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Synthesis and Characterization of Two Isostructural POCOP Ni(II) Pincer Complexes Containing Fluorothiophenolate Ligands: [Ni(SC6F4-4-H){C6H2-3-(C2H3O)-2,6-(OPiPr2)2}] and [Ni(SC6F5){C6H2-3-(C2H3O)-2,6-(OPiPr2)2}]

Synthesis and Characterization of Two Isostructural POCOP Ni(II) Pincer Complexes Containing... molbank Communication Synthesis and Characterization of Two Isostructural POCOP Ni(II) Pincer Complexes Containing Fluorothiophenolate Ligands: [Ni(SC F -4-H){C H -3-(C H O)-2,6-(OP Pr ) }] and 6 4 6 2 2 3 2 2 [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] 6 5 6 2 2 3 2 2 1 1 2 2 , Eric G. Morales-Espinosa , Naytze Ortiz-Pastrana , Valente Gómez-Benítez , Reyna Reyes-Martínez *, 2 2 3 Hilda Amelia Piñón-Castillo , Laura A. Manjarrez-Nevárez , Juan M. German-Acacio 1 , and David Morales-Morales * Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, Circuito Exterior, Coyoacán, Mexico City 04510, Mexico; erichsm536@yahoo.com.mx (E.G.M.-E.); nay_37@hotmail.com (N.O.-P.) Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua (UACH), Circuito Universitario S/N, C.P., Chihuahua 31125, Mexico; ebenitez@uach.mx (V.G.-B.); hpinon@uach.mx (H.A.P.-C.); lmanjarrez@uach.mx (L.A.M.-N.) Red de Apoyo a la Investigación, Coordinación de la Investigación Científica-UNAM, Instituto Nacional de Ciencias Médicas y Nutrición SZ, C.P., Mexico City 14000, Mexico; jmga@cic.unam.mx * Correspondence: rreyesm@uach.mx (R.R.-M.); damor@unam.mx (D.M.-M.) Citation: Morales-Espinosa, E.G.; Ortiz-Pastrana, N.; Gómez-Benítez, V.; Abstract: Among their many applications, metal pincer complexes are of interest for their properties Reyes-Martínez, R.; Piñón-Castillo, as catalysts in cross-coupling reactions. Pincer ligands exhibit tridentate coordination to the metal H.A.; Manjarrez-Nevárez, L.A.; center and occupy the meridional positions forming two chelate rings. The two Ni(II) POCOP pincer German-Acacio, J.M.; complexes with a fluorothiophenolate ligand reported herein, with formulas [Ni(SC F -4-H){C H - 6 4 6 2 Morales-Morales, D. Synthesis and i i 3-(C H O)-2,6-(OP Pr ) }] (2) and [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] (3), are isostructural. 2 3 2 2 6 5 6 2 2 3 2 2 Characterization of Two Isostructural Additionally, they are prepared in a facile manner from the chloride compound [NiCl{C H -3- POCOP Ni(II) Pincer Complexes 6 2 (C H O)-2-6-(OP Pr ) }] (1). The complexes exhibited slightly distorted square planar geometries Containing Fluorothiophenolate 2 3 2 2 Ligands: [Ni(SC F -4-H){C H -3- 6 4 6 2 around the metal. The fluorothiophenolate ligands are responsible of the C—HF, C—F and (C H O)-2,6-(OP Pr ) }] and 2 3 2 2 C=O interactions that contribute to stabilize the crystal structure arrays. [Ni(SC F ){C H -3-(C H O)-2,6- 6 5 6 2 2 3 (OP Pr ) }]. Molbank 2022, 2022, 2 2 Keywords: crystal structure; fluorothiophenolate; POCOP ligand; pincer compounds; catalysis; catalyst M1359. https://doi.org/ 10.3390/M1359 Academic Editor: René T. Boeré 1. Introduction Received: 21 January 2022 In general, pincer complexes are constituted by an anionic chelating tridentate ligand Accepted: 28 April 2022 coordinated in a meridional fashion, the anionic position is coordinated to the metal center Published: 9 May 2022 by a negatively charged atom, typically a carbon atom of the aryl ring [1,2]. While the Publisher’s Note: MDPI stays neutral other positions are occupied by linkers of the same ligand including donor atoms such as with regard to jurisdictional claims in N, P, O, S or Se, located in the pendant arms at the ortho positions to the carbon atom [3]. published maps and institutional affil- These characteristics provide stability and play a key role on the reactivity of the complexes iations. they form. These properties, in combination with the mere variation of the metal center, are responsible for the wide variety of applications that pincer compounds have found in different areas of chemistry, this being particularly true in the case of catalysis [4,5]. Over the last years, our research group has focused on the design, synthesis and use of Copyright: © 2022 by the authors. pincer-type ligands and their transition metal complexes [6–8], mainly due to the versatility Licensee MDPI, Basel, Switzerland. of applications that they may have in different areas such as catalysis [9,10], materials [11], This article is an open access article and medicine [12,13]. Resorcinol-based POCOP-type pincer complexes of group 10 adopt a distributed under the terms and square planar geometry [14,15]. Traditionally, complexes of these transition metals have conditions of the Creative Commons been used as efficient catalysts in C–C cross-coupling reactions, which are one of the most Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ important kinds of catalytic reactions to produce carbon–carbon bonds. These reactions 4.0/). have been traditionally catalyzed by Pd(II) species, however in recent years research has Molbank 2022, 2022, M1359. https://doi.org/10.3390/M1359 https://www.mdpi.com/journal/molbank Molbank 2022, 2022, M1359 2 of 10 been focused in the potential use of their analogous nickel compounds. Thus, given the aforementioned properties of pincer complexes, Ni(II) pincer compounds have been considered as a suitable alternative for this kind of couplings [16]. Among the pincer complexes, phosphinite POCOP pincer ligands and their complexes have proved to be very valuable, since they exhibit similar and often enhanced reactivity when compared to their phosphine counterparts and are easily synthesized from the direct reaction of resorcinol with a given chlorophosphine. The simplicity of this procedure allows by careful selection of a resorcinol derivative to produce pincer ligands substituted in the 3-position of the aryl ring, giving entrance to the production of non-symmetric pincer ligands and their complexes in a rather simple form [5]. Thus, following our continuous interest in the design of new pincer ligands, their complexes, and potential applications as well as our long-standing interest in the use of fluorothiophenolate moieties to fine tune both electronics and sterics in a given compound [17,18], we would like to present our findings in the synthesis, characterization and structural analysis of the two non-symmetric Ni(II)-POCOP pincer complexes [Ni(SC F -4-H){C H -3-(C H O)-2,6-(OP Pr ) }] (2) and 6 4 6 2 2 3 2 2 [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] (3). 6 5 6 2 2 3 2 2 2. Results and Discussion The title complexes were obtained in good yields through metathetical reaction be- tween the parent Ni(II)-POCOP pincer complex and the corresponding thiolate lead salt according to Scheme 1. The POCOP ligand L1 was produced from the direct reaction of 2,4-dihydroxyacetophenone with ClP Pr in a 1:2 molar ratio using and slight excess of triethylamine as base. Further, the Ni(II)-POCOP pincer compound [NiCl{C H -3-(C H O)- 6 2 2 3 2-6-(OP Pr ) }] (1) was obtained from the reaction of NiCl 6 H O in refluxing toluene [7]. 2 2 2 2 Finally, the POCOP pincer complexes including the fluorothiophenolate ligands [Ni(SC F - 6 4 i i 4-H){C H -3-(C H O)-2,6-(OP Pr ) }] (2) and [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] 6 2 2 3 2 2 6 5 6 2 2 3 2 2 (3) were prepared by metathesis reactions of the parent complex 1 with the lead salts of the corresponding thiophenolates ([Pb(SC F -4-H) ] and [Pb(SC F ) ]. In both cases, adequate 6 4 2 6 5 2 crystals were obtained by slow evaporation of CH Cl solutions of 2 and 3. The two pincer 2 2 complexes present the pincer ligand with a methylketone fragment in the 3-position of the phenyl ring. Both compounds crystalized in the centrosymmetric space group P21/n with very similar unit cell values (Table 1), intermolecular interactions and packing pat- terns, these characteristics suggesting isostructurality among the crystal structures. The asymmetric units are consistent of one molecule of the complex and four by unit cell. The coordination geometry around the metal centers Ni(II) in compounds 2 and 3 can be described as a slightly distorted square planar, as shown by the angles around the central atom that are different to 90 (Tables 2 and 3). The deviation from the best plane formed by coordination sphere (Ni1, S3, P1, C2 and P2 atoms) are of r.m.s. = 0.054 and 0.062 Å for complexes 2 and 3, respectively. The bond lengths and angles are similar in both complexes and the molecular structures including atom labels are shown in Figure 1. As expected, the POCOP ligands coordinate to the nickel center in a tridentate fashion via two phosphorus atoms (P1, P2) and one carbon (C2) atom, the ligand forming two chelating five-member rings (Ni–P–O–C–C) with bite angles P1–Ni1–C2 and P2–Ni1–C2 with values of 81.96 (14) and 82.12 (14) for complex 2, and 81.98 (8) and 82.13 (8) for complex 3. The chelate rings are near to coplanarity with the phenyl ring since the dihedral angles between the mean planes of the rings present values of 2.75 and 2.32 in complex 2, and of 1.84 and 1.48 in complex 3. The bond lengths of the coordinated pincer ligand are similar to other previously reported POCOP pincer complexes [19,20] (Tables 2 and 3). Completing the coordination sphere around the Ni(II) atoms one thiophenolate lig- and (S3), 2,3,5,6-tetrafluorothio phenolate ion ( SC F -4-H) in complex 2, and 2,3,4,5,6- 6 4 pentafluorothiophenolate ion ( SC F ) in complex 3. The fluorothiophenolate ligands 6 5 exhibit an orientation near to perpendicularity with the plane formed with the square plane geometry, having dihedral angles between the mean planes of 79.81 (16) and 76.26 (8) for compounds 2 and 3, respectively. The Ni1–S3 bond lengths are of 2.2054 (14) and Molbank 2022, 2022, M1359 3 of 10 2.2039 (9) Å with Ni1–S3–C21 angles of 112.37 (17) and 113.61 (10) for 2 and 3, respectively. The orientation of the thiolate ligand promotes the formation of intramolecular weak hy- drogen bond interactions of the type C–H between the methine (C12–H12) of one of the isopropyls and the fluorothiophenolate group (C21–C26) with distances of 3.095 Å in 2 and of 3.179 Å in 3. Intramolecular C–HS weak interactions between one methyl of the ligands and the sulfur atom as acceptor [C19–H19CS3, C19–H19BS3] (Tables 4 and 5) are also observed. Table 1. Crystallographic experimental details for (2) and (3). (2) CCDC 2142038 (3) CCDC 2142039 Crystal data Chemical formula C H F NiO P S C H F NiO P S 26 34 4 3 2 26 33 5 3 2 Mr 623.24 641.23 Crystal system, space group Monoclinic, P21/n Monoclinic, P21/n Temperature (K) 151 150 a, b, c (Å) 8.8138 (11), 10.0715 (13), 31.860 (4) 8.8159 (3), 10.1816 (3), 31.9637 (12) b ( ) 97.397 (4) 96.109 (2) 2804.6 (6) 2852.77 (17) V (Å3) Z 4 4 Radiation type Mo Ka Mo Ka m (mm ) 0.93 0.93 Crystal size (mm) 0.29  0.21  0.15 0.58  0.22  0.09 Data collection Bruker D8 Venture k geometry Bruker Smart Apex CCD Diffractometer diffractometer 208039-1 diffractometer 01-670-03 Absorption correction Analytical [21] Analytical [21] Tmin, Tmax 0.687, 0.820 0.616, 0.923 No. of measured, independent and 39113, 6919, 5212 38524, 6810, 5292 observed [I > 2s(I)] reflections Rint 0.080 0.080 (sin q/l)max (Å ) 0.667 0.658 Refinement 2 2 2 R[F > 2s (F )], wR(F ), S 0.069, 0.179, 1.11 0.048, 0.099, 1.09 No. of reflections 6919 6810 No. of parameters 343 352 H-atom parameters constrained 2 2 H-atom treatment w = 1/[s2(F ) + (0.0516P) + 13.4197P] H-atom parameters constrained 2 2 where P = (F + 2Fc )/3 1.78, 0.60 0.70, 0.34 Dr , Dr (e Å ) max min Computer programs: APEX2 v2014.1-1 [22], APEX2 v2012.10.0 [22], SAINT V8.34A [22], SAINT V8.27B [22], SHELXS2012 [23], SHELXL2014/7 [24], DIAMOND [25], publCIF [26]. Table 2. Selected geometric parameters (Å, ) for (2). Ni1–C2 1.898 (4) Ni1–P1 2.1662 (12) Ni1–P2 2.1524 (13) Ni1–S3 2.2054 (13) C2–Ni1–P2 82.12 (14) C2–Ni1–S3 169.35 (14) C2–Ni1–P1 81.95 (14) P2–Ni1–S3 90.55 (5) P2–Ni1–P1 163.94 (5) P1–Ni1–S3 104.93 (5) Table 3. Selected geometric parameters (Å, ) for (3). Ni1–C2 1.902 (3) Ni1–P1 2.1631 (8) Ni1–P2 2.1547 (8) Ni1–S3 2.2039 (8) C2–Ni1–P2 82.13 (8) C2–Ni1–S3 168.88 (9) C2–Ni1–P1 81.98 (9) P2–Ni1–S3 90.44 (3) P2–Ni1–P1 164.09 (3) P1–Ni1–S3 105.16 (3) Molbank 2022, 2022, M1359 4 of 10 Scheme 1. General synthesis of pincer complexes (2) and (3). Figure 1. The molecular structure of compounds (2) and (3), showing the atom labelling schemes. Displacement ellipsoids are drawn at 40% probability level. The intramolecular interactions are drawing as dashed lines. Molbank 2022, 2022, M1359 5 of 10 Table 4. Hydrogen-bond geometry (Å, ) for (2). D–H A D–H HA DA D–HA 0.98 2.50 3.352 (6) 145 C8–H8BF2 ii C10–H10AO3 0.98 2.47 3.418 (7) 163 C10–H10CF4 0.98 2.53 3.373 (7) 144 C13–H13CF1 0.98 2.50 3.307 (7) 140 iii C18–H18O2 1.00 2.64 3.615 (6) 164 C19–H19CS3 0.98 2.95 3.740 (5) 138 C20–H20BF1 0.98 2.59 3.572 (7) 176 Symmetry codes: (i) x + 1/2, y + 1/2, z + 3/2; (ii) x, y 1, z; (iii) x + 1, y + 2, z + 1. Table 5. Hydrogen-bond geometry (Å, ) for (3). D–HA D–H HA DA D–HA C8–H8CF2 0.98 2.49 3.312 (4) 141 ii 1.00 2.62 3.476 (3) 144 C9–H9F2 iii C10–H10AO3 0.98 2.52 3.458 (4) 160 C10–H10BF4 0.98 2.52 3.394 (4) 149 C13–H13BF1 0.98 2.59 3.325 (4) 132 C19–H19BS3 0.98 2.98 3.745 (3) 136 Symmetry codes: (i) x + 3/2, y 1/2, z + 1/2; (ii) x + 1, y, z; (iii) x, y + 1, z. Being both complexes isostructural the supramolecular arrangements are similar in both compounds. The presence of the fluorothiophenolate moieties give place to C–HF, C–F and C=O interactions. Additionally, two lone pair- interactions (lp-) were identified [27], the C7=O3Cg(C21–C26) interaction is formed by the carbonyl and the corresponding fluorothiophenolate group. The interaction exhibits a Ocentroid distance of 3.368 (5) Å in complex 2 and of 3.347 (3) Å in complex 3 (1 + x, 1 + y,z; 1 + x, 1 + y,z), these interactions generate one dimensional chains along the (110) direction (Figure 2). The other lp- interactions is formed between the F4 atom of the thiophenolate ligand and the phenyl ring (C1–C6) of the pincer ligand, the interactions FCg showed distance values of 3.410 (3) and 3.407 (2) Å for complexes 2 and 3 (x, 1 + y, z; x, 1 + y, z), respectively, the interaction is extended along the (010) direction producing linear chains (Figure 3). The supramolecular networks are complemented with C10—H10AO3=C7 interactions between a methyl and the ketone fragments. The combination of the two lp- interactions give place to a supramolecular layer parallel to the (110) plane as shown in Figure 4. Figure 2. Fragment of the structure of compound (2) showing the formation of C7=O3Cg(C21–C26) interaction (dashed lines). The hydrogen atoms have been omitted for clarity. The array exhibits two C–HF interactions (C9–H9F2 and C11–H11AF1) between one isopropyl and the fluorothiophenolate, forming an eight-membered cycle motif that is extended along the (100) direction forming chains (Figure 5). Additionally, a centrosym- metric eight-member cycle motif is also identified and is formed by the C18–H18O2 interaction, giving place to a dimer, these dimers are kept together by the C8–H8BF2 Molbank 2022, 2022, M1359 6 of 10 interaction giving place to a bidimensional array parallel to the (101) plane (Figure 6). The C9–H9F2 and C11–H11AF1, C18–H18O2 interactions interlink the layers formed by the lp- interactions (Figure 4) producing a three-dimensional crystal arrangement. Figure 3. Representation of the chains formed by the F4Cg(C1–26) and C10–H10AO3=C7 interac- tions. The H atoms not involved in these interactions have been omitted for clarity. Figure 4. The molecular packing of compound (2) showing the formation of C7=O3Cg(C21–C26) and F4Cg(C1–26) interactions parallel to the (110) plane. The hydrogen atoms are omitted. Figure 5. View of the linear array along the (100) direction due the C9–H9F2 and C11–H11AF1 interactions. Only the hydrogen atoms that participle in the interactions are drawn. Molbank 2022, 2022, M1359 7 of 10 Figure 6. Fragment of the molecular packing showing the C18–H18O2 and C8–H8BF2 interac- tions (dashed lines) forming a layer arrangement parallel to the (101) plane, H atoms not involved in these interactions have been omitted for clarity. The structural analysis of the isostructural Ni(II)-POCOP pincer compounds show that the inclusion of the fluorothiophenolate ligands, generate interactions like C–HF, C–Fp and C=O that contribute to the stabilization of the crystal packing. The presence of these interactions could contribute to modify the properties so can be used in catalyst, medicine, or material sciences to produce MOFs. 3. Materials and Methods 3.1. General All chemical reagents were obtained commercially and used as received without further purification. Melting points were recorded on a Mel-Temp II apparatus and are reported without correction. NMR spectra were recorded on a Bruker-Avance 300 MHz 1 13 1 31 1 spectrometer, the H, C{ H} and P{ H} NMR spectra were recorded at 300, 75.6 and 121.7 MHz, respectively. Chemical shifts are reported in p.p.m. () relative to the chemical 1 13 1 31 1 shift of the residual solvent (CDCl ) for H and C{ H}. P{ H} NMR spectra were recorded with complete proton decoupling using 85% H PO as an external standard. 3 4 Elemental analyses were performed in a Thermo Scientific (Waltham, MA, USA) Flash 2000 elemental analyzer, using a Mettler Toledo XP6 Automated-S Microbalance and sulfanilamide as standard (Thermo Scientific BN 217826, attained values N = 16.40%, C = 41.91%, H = 4.65%, y S = 18.63%; certified values N = 16.26%, C = 41.81%, H = 4.71%, y S = 18.62%). MS-DART experiments were recorded on a Jeol AccuTOF JMS-T100LC mass spectrometer. 3.2. Synthesis of the Ligand [C H -4-(C H O)-1-3-(OP Pr ) ] (L1) 6 2 2 3 2 2 A Schlenk flask was charged with 2,4-dihydroxyacetophenone (1.3 mmol), Et N (3.3 mmol) and 20 mL of dry THF. The resulting mixture was stirred for 30 min at room temperature and then a solution of ClP Pr (2.6 mmol) in 5 mL of THF was added dropwise. The mixture was then set to reflux for 12 h and allowed to cool down to room temperature Molbank 2022, 2022, M1359 8 of 10 before filtered via cannula. The solvent was removed from the filtrate under vacuum to afford ligand L1 as a colorless viscous oil. Identity and purity of the ligand was assessed by 31 1 P{ H} NMR. Thus, this compound was used in the next step without further purification. 31 1 Yield: 80%. P{ H} NMR (122 MHz, CDCl ):  148.2 and 148.8 p.p.m. 3.3. Synthesis of Complex [NiCl{C H -3-(C H O)-2-6-(OP Pr ) }] (1) 6 2 2 3 2 2 A solution of ligand L1 (0.5 mmol) in toluene (10 mL) was added dropwise to a suspension of NiCl 6H O (0.5 mmol) in toluene (20 mL). The resulting mixture was set 2 2 to reflux for 16 h. After this time, the solvent is removed under vacuum and the crude product purified by column chromatography (hexanes/AcOEt 8:2) to afford the pure complex 1 as a yellow microcrystalline solid. Yield: 68%, 0.162 g; m.p. 136–138 C. H NMR (300 MHz, CDCl ):  7.54 (d, 1H, J = 8.5 Hz), 6.40 (d, 1H, J = 8.5 Hz), 2.47 (s, 3H, CH ), 3 H,H H,H 3 2.46–2.29 (m, 4H, CH), 1.23–1.43 (m, 24H, CH ). C NMR (75 MHz, CDCl ):  196.41 (C=O), 3 3 172.20 (dd, J = 11.8, 8.2 Hz, Ar–O), 167.93 (dd, J = 12.4, 8.4 Hz, Ar–O), 131.01 (Ar–H), 126.63 (t, J = 20.9 Hz, Ar–Ni), 118.11 (dd, J = 8.6, 1.4 Hz, Ar–CO), 106.52 (dd, J = 9.9, 1.5 Hz, Ar–H), i i 31.31 (CH ), 27.83 (ddd, J = 14.9, 10.7, 6.8 Hz, CH Pr), 17.40 (dd, J = 10.8, 4.5 Hz, CH Pr), 3 3 i 31 2 16.76 (d, J = 23.1 Hz, CH Pr). P NMR (122 MHz, CDCl ):  190.84 (d, (AB) J = 328 Hz, 3 3 P,P 2 + 1P), 187.57 (d, (AB) J = 328 Hz, 1P). MS (DART) m/z: 478 [(100%) M+H] . Anal. Calcd P,P (%) for C H ClO P Ni: C, 50.30; H, 6.96. Found: C, 50.28; H, 6.71. 20 33 3 2 3.4. General Procedure for Synthesis of Complexes 2 and 3 To a solution of complex 1 (0.088 mmol) in CH Cl (10 mL), a solution of either 2 2 [Pb(SC F -4H) ] or [Pb(SC F ) ] (0.044 mmol) in acetone (20 mL) was added dropwise 6 4 2 6 5 2 under stirring. The resulting red-brick solution was stirred overnight. After this time the resulting reaction mixture was filtered through a short plug of Celite to remove the PbCl and the solvent was removed under vacuum and the residue recrystallized from CH Cl 2 2 affording in both cases yellow crystals, that were suitable for the X-ray diffraction analysis. 3.4.1. [Ni(SC F -4-H){C H -3-(C H O)-2,6-(OP Pr ) }] (2) 6 4 6 2 2 3 i 2 2 Yield: 93%, 0.051 g; m.p. 131–134 C. H NMR (300 MHz, CDCl ):  7.58 (d, 1H, J = 8.5 Hz), 6.65 (m, 1H), 6.46 (d, 1H, J = 8.5 Hz), 2.48 (s, 3H, CH ), 2.01–2.15 (m, 4H, H,H H,H 3 31 2 CH), 1.19–1.32 (m, 24H, CH ). P NMR (122 MHz, CDCl ):  194.21 (d, (AB) J = 293 Hz, 3 3 P,P 2 19 1P), 191.05 (d, (AB) J = 293 Hz, 1P). F NMR (283 MHz, CDCl ):  131.54–131.72 P,P 3 (m, o-F), 140.81–141.00 (m, m-F). MS (DART) m/z: 624 [(100%) M+H] . Anal. Calcd (%) for C H F NiO P S: C, 50.11; H, 5.50. Found: C, 50.13; H, 5.52. 26 34 4 3 2 3.4.2. [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] (3) 6 5 6 2 2 3 i 2 2 Yield: 90%, 0.050 g; m.p. 145–149 C. H NMR (300 MHz, CDCl ): 7.58 (d, 1H, J = 8.5 Hz), 6.46 (d, 1H, J = 8.5 Hz), 2.48 (s, 3H, CH ), 1.99–2.16 (m, 4H, CH), H,H H,H 3 31 2 1.13–1.36 (m, 24H, CH ). P NMR (122 MHz, CDCl ):  194.38 (d, (AB) J = 292 Hz, 1P), 3 3 P,P 2 19 191.22 (d, (AB) J = 292 Hz, 1P). F NMR (283 MHz, CDCl ):  130.99–131.16 (m, o-F), P,P 3 161.08–161.35 (m, p-F), 163.61–163.95 (m, m-F). MS (DART) m/z: 642 [(100%) M+H] . Anal. Calcd (%) for C H F NiO P S: C, 48.70; H, 5.19. Found: C, 48.69; H, 5.17. 26 33 5 3 2 3.5. Refinement Crystal data, data collection and structure refinement details are summarized in Table 1. Carbon-bound H atoms were positioned geometrically and included as riding atoms, with C–H = 0.98 Å with U (H) values of 1.5U (C) for methyl H, and C–H = 0.95 Å and 1.00 Å iso eq with U (H) values of 1.2 U (C) for methine. For more information about the structures of eq iso compounds 2 and 3, please refer to Supplementary Materials, as the picture shows 4. Conclusions Thus, in conclusion, we have provided a facile procedure for the synthesis of two Ni(II) pincer complexes including fluorinated thiolates on their structures. The complexes Molbank 2022, 2022, M1359 9 of 10 were fully characterized both in solution and solid state. Further analysis in the solid state revealed some interesting features that can be useful for the further development of these species and potential uses in catalysis, medicinal chemistry and materials sciences, some of these possibilities being currently explored in our laboratories. Supplementary Materials: The following supporting information can be downloaded. Supplemen- tary data for complexes (2) and (3) has been deposited at the Cambridge Crystallographic Data Centre. Copies of this information are available free of charge on request from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax: +44-1223-336033; e-mail deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk (accessed on 21 January 2022), quoting the deposition numbers CCDC 2142038-2142039. Author Contributions: Conceptualization, D.M.-M. and R.R.-M.; methodology, E.G.M.-E., R.R.-M., V.G.-B., J.M.G.-A. and N.O.-P.; software, N.O.-P., J.M.G.-A. and R.R.-M.; validation, D.M.-M., N.O.-P., J.M.G.-A. and R.R.-M.; formal analysis, D.M.-M., N.O.-P., J.M.G.-A. and R.R.-M.; investigation, E.G.M.-E., R.R.-M., V.G.-B. and N.O.-P.; resources, D.M.-M.; data curation, D.M.-M., R.R.-M. and E.G.M.-E.; writing—original draft preparation, D.M.-M., R.R.-M., E.G.M.-E., H.A.P.-C., L.A.M.-N.; writing—review and editing, D.M.-M. and R.R.-M.; visualization, N.O.-P. and R.R.-M.; supervision, D.M.-M. and R.R.-M.; project administration, D.M.-M.; funding acquisition, D.M.-M. All authors have read and agreed to the published version of the manuscript. Funding: Programa de Becas Posdoctorales-DGAPA-UNAM (Oficios: CJIC/CTIC/4064/2015 and CJIC/CTIC/4652/2016, respectively). CONACYT (grant NoA1-S-033933), PAPIIT (grant NoIN210520) and Subsecretaria de Eduacion Superior (PRODEP) grant OF-17-8204. Data Availability Statement: Not applicable. Acknowledgments: We would like to thank Simon Hernandez-Ortega, Chem. EngLuis Velasco Ibarra, Francisco Javier Pérez Flores, Q. Eréndira García Ríos, Lucia del Carmen Márquez Alonso, Lucero Ríos Ruiz, Alejandra Núñez Pineda (CCIQS), Q. María de la Paz Orta Pérez, Naytze Ortiz- Pastrana and Q. Roció Patiño-Maya for technical assistance. Conflicts of Interest: The authors declare no conflict of interest. Additionally, the funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the result. References 1. Morales-Morales, D. The chemistry of PCP pincer phosphinite transition metal complexes. In The Chemistry of the Pincer Compounds, 1st ed.; Morales-Morales, D., Jensen, C.M., Eds.; Elsevier: Amsterdam, The Netherlands, 2007; pp. 151–180. 2. Albrecht, M.; Morales-Morales, D. Pincer-Type Iridium Complexes for Organic Transformations. In Iridium Complexes in Organic Synthesis, 1st ed.; Oro, L.A., Claver, C., Eds.; Wiley-VCH: Weinheim, Germany, 2009; pp. 299–323. 3. Valdés, H.; González-Sebastián, L.; Morales-Morales, D. Aromatic para-functionalized NCN pincer compounds. J. Organomet. Chem. 2017, 845, 229–257. [CrossRef] 4. Morales-Morales, D. Pincer Complexes. Applications in Catalysis. Rev. Soc. Quim. Mex. 2004, 48, 338–346. [CrossRef] 5. Asay, M.; Morales-Morales, D. Non-symmetric pincer ligands: Complexes and applications in catalysis. Dalton Trans. 2015, 44, 17432–17447. [CrossRef] [PubMed] 6. Estudiante-Negrete, F.; Hernández-Ortega, S.; Morales-Morales, D. Ni(II)–POCOP pincer compound [NiCl{C H -2,10-(OPPh ) }] 10 5 2 2 an efficient and robust nickel catalyst for the Suzuki–Miyaura coupling reactions. Inorg. Chim. Acta 2012, 387, 58–63. [CrossRef] 7. Solano-Prado, M.A.; Estudiante-Negrete, F.; Morales-Morales, D. Group 10 phosphinite POCOP pincer complexes derived from 4-n-dodecylresorcinol: An alternative way to produce non-symmetric pincer compounds. Polyhedron 2010, 29, 592–600. [CrossRef] 8. Basauri-Molina, M.; Hernández-Ortega, S.; Morales-Morales, D. Microwave-Assisted C–C and C–S Couplings Catalysed by Organometallic Pd-SCS or Coordination Ni-SNS Pincer Complexes. Eur. J. Inorg. Chem. 2014, 4619–4625. [CrossRef] 9. Suzuki, T. Organic Synthesis Involving Iridium-Catalyzed Oxidation. Chem. Rev. 2011, 111, 1825–1845. [CrossRef] 10. Gunanathan, C.; Milstein, D. Bond Activation and Catalysis by Ruthenium Pincer Complexes. Chem. Rev. 2014, 114, 12024–12087. [CrossRef] 11. Brown, D.G.; Schauer, P.A.; Borau-Garcia, J.; Fancy, B.R.; Berlinguette, C.P. Stabilization of Ruthenium Sensitizers to TiO2 Surfaces through Cooperative Anchoring Groups. J. Am. Chem. Soc. 2013, 135, 1692–1695. [CrossRef] 12. Ramírez-Rave, S.; Ramírez-Apan, M.T.; Tlahuext, H.; Morales-Morales, D.; Toscano, R.A.; Grevy, J.M. Non-symmetric CNS- Pt(II) pincer complexes including thioether functionalized iminophosphoranes. Evaluation of their in vitro anticancer activity. J. Organomet. Chem. 2016, 814, 16–24. [CrossRef] Molbank 2022, 2022, M1359 10 of 10 13. Tabrizi, L.; Chiniforoshan, H. New platinum(II) complexes of CCC-pincer N-heterocyclic carbene ligand: Synthesis, characteriza- tion, cytotoxicity and antileishmanial activity. J. Organomet. Chem. 2016, 818, 98–105. [CrossRef] 14. Choi, J.; MacArthur, A.H.R.; Brookhart, M.; Goldman, A.S. Dehydrogenation and Related Reactions Catalyzed by Iridium Pincer Complexes. Chem. Rev. 2011, 111, 1761–1779. [CrossRef] 15. Selander, N.; Szabó, K.J. Catalysis by Palladium Pincer Complexes. Chem. Rev. 2011, 111, 2048–2076. [CrossRef] 16. Asay, M.; Morales-Morales, D. Recent Advances on the Chemistry of POCOP–Nickel Pincer Compounds. Top. Organomet. Chem. 2006, 54, 239–268. 17. Olivos-Suárez, A.I.; Ríos-Moreno, G.; Hernández-Ortega, S.; Toscano, R.A.; García, J.J.; Morales-Morales, D. Reactivity of fluorinated thioether ligands of the type [C H Br-2-(CH SR )] towards transition metal complexes of the group 10. Inorg. Chim. 6 4 2 F Acta. 2007, 360, 4133–4141. [CrossRef] 18. Baldovino-Pantaleón, O.; Hernández-Ortega, S.; Reyes-Martínez, R.; Morales-Morales, D. A second monoclinic polymorph of 3 0 {2,6-bis[(2,4,5-trifluorophenyl) iminomethyl]pyridine- N,N ,N”} dichloridonickel(II). Acta Cryst. 2012, E68, m134. 19. García-Eleno, M.A.; Padilla-Mata, E.; Estudiante-Negrete, F.; Pichal-Cerda, F.; Hernández-Ortega, S.; Toscano, R.A.; Morales- Morales, D. Single step, high yield synthesis of para-hydroxy functionalized POCOP ligands and their Ni(II) pincer derivatives. New J. Chem. 2015, 39, 3361–3365. [CrossRef] 20. García-Eleno, M.A.; Quezada-Miriel, M.; Reyes-Martínez, R.; Hernández-Ortega, S.; Morales-Morales, D. A compara- tive study of the packing of two polymorphs of the nickel(II) pincer complex [2,6-bis(di-tert-butylphosphinoyl)-4-(3,5- dinitrobenzoyloxy)phenyl- P,C1,P’]chloridonickel(II). Acta Cryst. 2016, C72, 393–397. [CrossRef] 21. Sheldrick, G.M. SADABS; University of Göttingen: Göttingen, Germany, 1996. 22. Bruker. APEX2, SAINT; Bruker AXS Inc.: Madison, WI, USA, 2012. 23. Sheldrick, G.M. A short history of SHELX. Acta Cryst. 2008, A64, 112–122. [CrossRef] 24. Sheldrick, G.M. Crystal structure refinement with SHELXL. Acta Cryst. 2015, C71, 3–8. 25. Brandenburg, K. Diamond; Crystal Impact GbR: Bonn, Germany, 2006. 26. Westrip, S.P.J. publCIF: Software for editing, validating and formatting crystallographic information files. Appl. Cryst. 2010, 43, 920–925. [CrossRef] 27. Mooibroek, T.J.; Gamez, P.; Reedijk, J. Lone pair– interactions: A new supramolecular bond? CrystEngComm 2008, 10, 1501–1515. 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Synthesis and Characterization of Two Isostructural POCOP Ni(II) Pincer Complexes Containing Fluorothiophenolate Ligands: [Ni(SC6F4-4-H){C6H2-3-(C2H3O)-2,6-(OPiPr2)2}] and [Ni(SC6F5){C6H2-3-(C2H3O)-2,6-(OPiPr2)2}]

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molbank Communication Synthesis and Characterization of Two Isostructural POCOP Ni(II) Pincer Complexes Containing Fluorothiophenolate Ligands: [Ni(SC F -4-H){C H -3-(C H O)-2,6-(OP Pr ) }] and 6 4 6 2 2 3 2 2 [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] 6 5 6 2 2 3 2 2 1 1 2 2 , Eric G. Morales-Espinosa , Naytze Ortiz-Pastrana , Valente Gómez-Benítez , Reyna Reyes-Martínez *, 2 2 3 Hilda Amelia Piñón-Castillo , Laura A. Manjarrez-Nevárez , Juan M. German-Acacio 1 , and David Morales-Morales * Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, Circuito Exterior, Coyoacán, Mexico City 04510, Mexico; erichsm536@yahoo.com.mx (E.G.M.-E.); nay_37@hotmail.com (N.O.-P.) Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua (UACH), Circuito Universitario S/N, C.P., Chihuahua 31125, Mexico; ebenitez@uach.mx (V.G.-B.); hpinon@uach.mx (H.A.P.-C.); lmanjarrez@uach.mx (L.A.M.-N.) Red de Apoyo a la Investigación, Coordinación de la Investigación Científica-UNAM, Instituto Nacional de Ciencias Médicas y Nutrición SZ, C.P., Mexico City 14000, Mexico; jmga@cic.unam.mx * Correspondence: rreyesm@uach.mx (R.R.-M.); damor@unam.mx (D.M.-M.) Citation: Morales-Espinosa, E.G.; Ortiz-Pastrana, N.; Gómez-Benítez, V.; Abstract: Among their many applications, metal pincer complexes are of interest for their properties Reyes-Martínez, R.; Piñón-Castillo, as catalysts in cross-coupling reactions. Pincer ligands exhibit tridentate coordination to the metal H.A.; Manjarrez-Nevárez, L.A.; center and occupy the meridional positions forming two chelate rings. The two Ni(II) POCOP pincer German-Acacio, J.M.; complexes with a fluorothiophenolate ligand reported herein, with formulas [Ni(SC F -4-H){C H - 6 4 6 2 Morales-Morales, D. Synthesis and i i 3-(C H O)-2,6-(OP Pr ) }] (2) and [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] (3), are isostructural. 2 3 2 2 6 5 6 2 2 3 2 2 Characterization of Two Isostructural Additionally, they are prepared in a facile manner from the chloride compound [NiCl{C H -3- POCOP Ni(II) Pincer Complexes 6 2 (C H O)-2-6-(OP Pr ) }] (1). The complexes exhibited slightly distorted square planar geometries Containing Fluorothiophenolate 2 3 2 2 Ligands: [Ni(SC F -4-H){C H -3- 6 4 6 2 around the metal. The fluorothiophenolate ligands are responsible of the C—HF, C—F and (C H O)-2,6-(OP Pr ) }] and 2 3 2 2 C=O interactions that contribute to stabilize the crystal structure arrays. [Ni(SC F ){C H -3-(C H O)-2,6- 6 5 6 2 2 3 (OP Pr ) }]. Molbank 2022, 2022, 2 2 Keywords: crystal structure; fluorothiophenolate; POCOP ligand; pincer compounds; catalysis; catalyst M1359. https://doi.org/ 10.3390/M1359 Academic Editor: René T. Boeré 1. Introduction Received: 21 January 2022 In general, pincer complexes are constituted by an anionic chelating tridentate ligand Accepted: 28 April 2022 coordinated in a meridional fashion, the anionic position is coordinated to the metal center Published: 9 May 2022 by a negatively charged atom, typically a carbon atom of the aryl ring [1,2]. While the Publisher’s Note: MDPI stays neutral other positions are occupied by linkers of the same ligand including donor atoms such as with regard to jurisdictional claims in N, P, O, S or Se, located in the pendant arms at the ortho positions to the carbon atom [3]. published maps and institutional affil- These characteristics provide stability and play a key role on the reactivity of the complexes iations. they form. These properties, in combination with the mere variation of the metal center, are responsible for the wide variety of applications that pincer compounds have found in different areas of chemistry, this being particularly true in the case of catalysis [4,5]. Over the last years, our research group has focused on the design, synthesis and use of Copyright: © 2022 by the authors. pincer-type ligands and their transition metal complexes [6–8], mainly due to the versatility Licensee MDPI, Basel, Switzerland. of applications that they may have in different areas such as catalysis [9,10], materials [11], This article is an open access article and medicine [12,13]. Resorcinol-based POCOP-type pincer complexes of group 10 adopt a distributed under the terms and square planar geometry [14,15]. Traditionally, complexes of these transition metals have conditions of the Creative Commons been used as efficient catalysts in C–C cross-coupling reactions, which are one of the most Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ important kinds of catalytic reactions to produce carbon–carbon bonds. These reactions 4.0/). have been traditionally catalyzed by Pd(II) species, however in recent years research has Molbank 2022, 2022, M1359. https://doi.org/10.3390/M1359 https://www.mdpi.com/journal/molbank Molbank 2022, 2022, M1359 2 of 10 been focused in the potential use of their analogous nickel compounds. Thus, given the aforementioned properties of pincer complexes, Ni(II) pincer compounds have been considered as a suitable alternative for this kind of couplings [16]. Among the pincer complexes, phosphinite POCOP pincer ligands and their complexes have proved to be very valuable, since they exhibit similar and often enhanced reactivity when compared to their phosphine counterparts and are easily synthesized from the direct reaction of resorcinol with a given chlorophosphine. The simplicity of this procedure allows by careful selection of a resorcinol derivative to produce pincer ligands substituted in the 3-position of the aryl ring, giving entrance to the production of non-symmetric pincer ligands and their complexes in a rather simple form [5]. Thus, following our continuous interest in the design of new pincer ligands, their complexes, and potential applications as well as our long-standing interest in the use of fluorothiophenolate moieties to fine tune both electronics and sterics in a given compound [17,18], we would like to present our findings in the synthesis, characterization and structural analysis of the two non-symmetric Ni(II)-POCOP pincer complexes [Ni(SC F -4-H){C H -3-(C H O)-2,6-(OP Pr ) }] (2) and 6 4 6 2 2 3 2 2 [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] (3). 6 5 6 2 2 3 2 2 2. Results and Discussion The title complexes were obtained in good yields through metathetical reaction be- tween the parent Ni(II)-POCOP pincer complex and the corresponding thiolate lead salt according to Scheme 1. The POCOP ligand L1 was produced from the direct reaction of 2,4-dihydroxyacetophenone with ClP Pr in a 1:2 molar ratio using and slight excess of triethylamine as base. Further, the Ni(II)-POCOP pincer compound [NiCl{C H -3-(C H O)- 6 2 2 3 2-6-(OP Pr ) }] (1) was obtained from the reaction of NiCl 6 H O in refluxing toluene [7]. 2 2 2 2 Finally, the POCOP pincer complexes including the fluorothiophenolate ligands [Ni(SC F - 6 4 i i 4-H){C H -3-(C H O)-2,6-(OP Pr ) }] (2) and [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] 6 2 2 3 2 2 6 5 6 2 2 3 2 2 (3) were prepared by metathesis reactions of the parent complex 1 with the lead salts of the corresponding thiophenolates ([Pb(SC F -4-H) ] and [Pb(SC F ) ]. In both cases, adequate 6 4 2 6 5 2 crystals were obtained by slow evaporation of CH Cl solutions of 2 and 3. The two pincer 2 2 complexes present the pincer ligand with a methylketone fragment in the 3-position of the phenyl ring. Both compounds crystalized in the centrosymmetric space group P21/n with very similar unit cell values (Table 1), intermolecular interactions and packing pat- terns, these characteristics suggesting isostructurality among the crystal structures. The asymmetric units are consistent of one molecule of the complex and four by unit cell. The coordination geometry around the metal centers Ni(II) in compounds 2 and 3 can be described as a slightly distorted square planar, as shown by the angles around the central atom that are different to 90 (Tables 2 and 3). The deviation from the best plane formed by coordination sphere (Ni1, S3, P1, C2 and P2 atoms) are of r.m.s. = 0.054 and 0.062 Å for complexes 2 and 3, respectively. The bond lengths and angles are similar in both complexes and the molecular structures including atom labels are shown in Figure 1. As expected, the POCOP ligands coordinate to the nickel center in a tridentate fashion via two phosphorus atoms (P1, P2) and one carbon (C2) atom, the ligand forming two chelating five-member rings (Ni–P–O–C–C) with bite angles P1–Ni1–C2 and P2–Ni1–C2 with values of 81.96 (14) and 82.12 (14) for complex 2, and 81.98 (8) and 82.13 (8) for complex 3. The chelate rings are near to coplanarity with the phenyl ring since the dihedral angles between the mean planes of the rings present values of 2.75 and 2.32 in complex 2, and of 1.84 and 1.48 in complex 3. The bond lengths of the coordinated pincer ligand are similar to other previously reported POCOP pincer complexes [19,20] (Tables 2 and 3). Completing the coordination sphere around the Ni(II) atoms one thiophenolate lig- and (S3), 2,3,5,6-tetrafluorothio phenolate ion ( SC F -4-H) in complex 2, and 2,3,4,5,6- 6 4 pentafluorothiophenolate ion ( SC F ) in complex 3. The fluorothiophenolate ligands 6 5 exhibit an orientation near to perpendicularity with the plane formed with the square plane geometry, having dihedral angles between the mean planes of 79.81 (16) and 76.26 (8) for compounds 2 and 3, respectively. The Ni1–S3 bond lengths are of 2.2054 (14) and Molbank 2022, 2022, M1359 3 of 10 2.2039 (9) Å with Ni1–S3–C21 angles of 112.37 (17) and 113.61 (10) for 2 and 3, respectively. The orientation of the thiolate ligand promotes the formation of intramolecular weak hy- drogen bond interactions of the type C–H between the methine (C12–H12) of one of the isopropyls and the fluorothiophenolate group (C21–C26) with distances of 3.095 Å in 2 and of 3.179 Å in 3. Intramolecular C–HS weak interactions between one methyl of the ligands and the sulfur atom as acceptor [C19–H19CS3, C19–H19BS3] (Tables 4 and 5) are also observed. Table 1. Crystallographic experimental details for (2) and (3). (2) CCDC 2142038 (3) CCDC 2142039 Crystal data Chemical formula C H F NiO P S C H F NiO P S 26 34 4 3 2 26 33 5 3 2 Mr 623.24 641.23 Crystal system, space group Monoclinic, P21/n Monoclinic, P21/n Temperature (K) 151 150 a, b, c (Å) 8.8138 (11), 10.0715 (13), 31.860 (4) 8.8159 (3), 10.1816 (3), 31.9637 (12) b ( ) 97.397 (4) 96.109 (2) 2804.6 (6) 2852.77 (17) V (Å3) Z 4 4 Radiation type Mo Ka Mo Ka m (mm ) 0.93 0.93 Crystal size (mm) 0.29  0.21  0.15 0.58  0.22  0.09 Data collection Bruker D8 Venture k geometry Bruker Smart Apex CCD Diffractometer diffractometer 208039-1 diffractometer 01-670-03 Absorption correction Analytical [21] Analytical [21] Tmin, Tmax 0.687, 0.820 0.616, 0.923 No. of measured, independent and 39113, 6919, 5212 38524, 6810, 5292 observed [I > 2s(I)] reflections Rint 0.080 0.080 (sin q/l)max (Å ) 0.667 0.658 Refinement 2 2 2 R[F > 2s (F )], wR(F ), S 0.069, 0.179, 1.11 0.048, 0.099, 1.09 No. of reflections 6919 6810 No. of parameters 343 352 H-atom parameters constrained 2 2 H-atom treatment w = 1/[s2(F ) + (0.0516P) + 13.4197P] H-atom parameters constrained 2 2 where P = (F + 2Fc )/3 1.78, 0.60 0.70, 0.34 Dr , Dr (e Å ) max min Computer programs: APEX2 v2014.1-1 [22], APEX2 v2012.10.0 [22], SAINT V8.34A [22], SAINT V8.27B [22], SHELXS2012 [23], SHELXL2014/7 [24], DIAMOND [25], publCIF [26]. Table 2. Selected geometric parameters (Å, ) for (2). Ni1–C2 1.898 (4) Ni1–P1 2.1662 (12) Ni1–P2 2.1524 (13) Ni1–S3 2.2054 (13) C2–Ni1–P2 82.12 (14) C2–Ni1–S3 169.35 (14) C2–Ni1–P1 81.95 (14) P2–Ni1–S3 90.55 (5) P2–Ni1–P1 163.94 (5) P1–Ni1–S3 104.93 (5) Table 3. Selected geometric parameters (Å, ) for (3). Ni1–C2 1.902 (3) Ni1–P1 2.1631 (8) Ni1–P2 2.1547 (8) Ni1–S3 2.2039 (8) C2–Ni1–P2 82.13 (8) C2–Ni1–S3 168.88 (9) C2–Ni1–P1 81.98 (9) P2–Ni1–S3 90.44 (3) P2–Ni1–P1 164.09 (3) P1–Ni1–S3 105.16 (3) Molbank 2022, 2022, M1359 4 of 10 Scheme 1. General synthesis of pincer complexes (2) and (3). Figure 1. The molecular structure of compounds (2) and (3), showing the atom labelling schemes. Displacement ellipsoids are drawn at 40% probability level. The intramolecular interactions are drawing as dashed lines. Molbank 2022, 2022, M1359 5 of 10 Table 4. Hydrogen-bond geometry (Å, ) for (2). D–H A D–H HA DA D–HA 0.98 2.50 3.352 (6) 145 C8–H8BF2 ii C10–H10AO3 0.98 2.47 3.418 (7) 163 C10–H10CF4 0.98 2.53 3.373 (7) 144 C13–H13CF1 0.98 2.50 3.307 (7) 140 iii C18–H18O2 1.00 2.64 3.615 (6) 164 C19–H19CS3 0.98 2.95 3.740 (5) 138 C20–H20BF1 0.98 2.59 3.572 (7) 176 Symmetry codes: (i) x + 1/2, y + 1/2, z + 3/2; (ii) x, y 1, z; (iii) x + 1, y + 2, z + 1. Table 5. Hydrogen-bond geometry (Å, ) for (3). D–HA D–H HA DA D–HA C8–H8CF2 0.98 2.49 3.312 (4) 141 ii 1.00 2.62 3.476 (3) 144 C9–H9F2 iii C10–H10AO3 0.98 2.52 3.458 (4) 160 C10–H10BF4 0.98 2.52 3.394 (4) 149 C13–H13BF1 0.98 2.59 3.325 (4) 132 C19–H19BS3 0.98 2.98 3.745 (3) 136 Symmetry codes: (i) x + 3/2, y 1/2, z + 1/2; (ii) x + 1, y, z; (iii) x, y + 1, z. Being both complexes isostructural the supramolecular arrangements are similar in both compounds. The presence of the fluorothiophenolate moieties give place to C–HF, C–F and C=O interactions. Additionally, two lone pair- interactions (lp-) were identified [27], the C7=O3Cg(C21–C26) interaction is formed by the carbonyl and the corresponding fluorothiophenolate group. The interaction exhibits a Ocentroid distance of 3.368 (5) Å in complex 2 and of 3.347 (3) Å in complex 3 (1 + x, 1 + y,z; 1 + x, 1 + y,z), these interactions generate one dimensional chains along the (110) direction (Figure 2). The other lp- interactions is formed between the F4 atom of the thiophenolate ligand and the phenyl ring (C1–C6) of the pincer ligand, the interactions FCg showed distance values of 3.410 (3) and 3.407 (2) Å for complexes 2 and 3 (x, 1 + y, z; x, 1 + y, z), respectively, the interaction is extended along the (010) direction producing linear chains (Figure 3). The supramolecular networks are complemented with C10—H10AO3=C7 interactions between a methyl and the ketone fragments. The combination of the two lp- interactions give place to a supramolecular layer parallel to the (110) plane as shown in Figure 4. Figure 2. Fragment of the structure of compound (2) showing the formation of C7=O3Cg(C21–C26) interaction (dashed lines). The hydrogen atoms have been omitted for clarity. The array exhibits two C–HF interactions (C9–H9F2 and C11–H11AF1) between one isopropyl and the fluorothiophenolate, forming an eight-membered cycle motif that is extended along the (100) direction forming chains (Figure 5). Additionally, a centrosym- metric eight-member cycle motif is also identified and is formed by the C18–H18O2 interaction, giving place to a dimer, these dimers are kept together by the C8–H8BF2 Molbank 2022, 2022, M1359 6 of 10 interaction giving place to a bidimensional array parallel to the (101) plane (Figure 6). The C9–H9F2 and C11–H11AF1, C18–H18O2 interactions interlink the layers formed by the lp- interactions (Figure 4) producing a three-dimensional crystal arrangement. Figure 3. Representation of the chains formed by the F4Cg(C1–26) and C10–H10AO3=C7 interac- tions. The H atoms not involved in these interactions have been omitted for clarity. Figure 4. The molecular packing of compound (2) showing the formation of C7=O3Cg(C21–C26) and F4Cg(C1–26) interactions parallel to the (110) plane. The hydrogen atoms are omitted. Figure 5. View of the linear array along the (100) direction due the C9–H9F2 and C11–H11AF1 interactions. Only the hydrogen atoms that participle in the interactions are drawn. Molbank 2022, 2022, M1359 7 of 10 Figure 6. Fragment of the molecular packing showing the C18–H18O2 and C8–H8BF2 interac- tions (dashed lines) forming a layer arrangement parallel to the (101) plane, H atoms not involved in these interactions have been omitted for clarity. The structural analysis of the isostructural Ni(II)-POCOP pincer compounds show that the inclusion of the fluorothiophenolate ligands, generate interactions like C–HF, C–Fp and C=O that contribute to the stabilization of the crystal packing. The presence of these interactions could contribute to modify the properties so can be used in catalyst, medicine, or material sciences to produce MOFs. 3. Materials and Methods 3.1. General All chemical reagents were obtained commercially and used as received without further purification. Melting points were recorded on a Mel-Temp II apparatus and are reported without correction. NMR spectra were recorded on a Bruker-Avance 300 MHz 1 13 1 31 1 spectrometer, the H, C{ H} and P{ H} NMR spectra were recorded at 300, 75.6 and 121.7 MHz, respectively. Chemical shifts are reported in p.p.m. () relative to the chemical 1 13 1 31 1 shift of the residual solvent (CDCl ) for H and C{ H}. P{ H} NMR spectra were recorded with complete proton decoupling using 85% H PO as an external standard. 3 4 Elemental analyses were performed in a Thermo Scientific (Waltham, MA, USA) Flash 2000 elemental analyzer, using a Mettler Toledo XP6 Automated-S Microbalance and sulfanilamide as standard (Thermo Scientific BN 217826, attained values N = 16.40%, C = 41.91%, H = 4.65%, y S = 18.63%; certified values N = 16.26%, C = 41.81%, H = 4.71%, y S = 18.62%). MS-DART experiments were recorded on a Jeol AccuTOF JMS-T100LC mass spectrometer. 3.2. Synthesis of the Ligand [C H -4-(C H O)-1-3-(OP Pr ) ] (L1) 6 2 2 3 2 2 A Schlenk flask was charged with 2,4-dihydroxyacetophenone (1.3 mmol), Et N (3.3 mmol) and 20 mL of dry THF. The resulting mixture was stirred for 30 min at room temperature and then a solution of ClP Pr (2.6 mmol) in 5 mL of THF was added dropwise. The mixture was then set to reflux for 12 h and allowed to cool down to room temperature Molbank 2022, 2022, M1359 8 of 10 before filtered via cannula. The solvent was removed from the filtrate under vacuum to afford ligand L1 as a colorless viscous oil. Identity and purity of the ligand was assessed by 31 1 P{ H} NMR. Thus, this compound was used in the next step without further purification. 31 1 Yield: 80%. P{ H} NMR (122 MHz, CDCl ):  148.2 and 148.8 p.p.m. 3.3. Synthesis of Complex [NiCl{C H -3-(C H O)-2-6-(OP Pr ) }] (1) 6 2 2 3 2 2 A solution of ligand L1 (0.5 mmol) in toluene (10 mL) was added dropwise to a suspension of NiCl 6H O (0.5 mmol) in toluene (20 mL). The resulting mixture was set 2 2 to reflux for 16 h. After this time, the solvent is removed under vacuum and the crude product purified by column chromatography (hexanes/AcOEt 8:2) to afford the pure complex 1 as a yellow microcrystalline solid. Yield: 68%, 0.162 g; m.p. 136–138 C. H NMR (300 MHz, CDCl ):  7.54 (d, 1H, J = 8.5 Hz), 6.40 (d, 1H, J = 8.5 Hz), 2.47 (s, 3H, CH ), 3 H,H H,H 3 2.46–2.29 (m, 4H, CH), 1.23–1.43 (m, 24H, CH ). C NMR (75 MHz, CDCl ):  196.41 (C=O), 3 3 172.20 (dd, J = 11.8, 8.2 Hz, Ar–O), 167.93 (dd, J = 12.4, 8.4 Hz, Ar–O), 131.01 (Ar–H), 126.63 (t, J = 20.9 Hz, Ar–Ni), 118.11 (dd, J = 8.6, 1.4 Hz, Ar–CO), 106.52 (dd, J = 9.9, 1.5 Hz, Ar–H), i i 31.31 (CH ), 27.83 (ddd, J = 14.9, 10.7, 6.8 Hz, CH Pr), 17.40 (dd, J = 10.8, 4.5 Hz, CH Pr), 3 3 i 31 2 16.76 (d, J = 23.1 Hz, CH Pr). P NMR (122 MHz, CDCl ):  190.84 (d, (AB) J = 328 Hz, 3 3 P,P 2 + 1P), 187.57 (d, (AB) J = 328 Hz, 1P). MS (DART) m/z: 478 [(100%) M+H] . Anal. Calcd P,P (%) for C H ClO P Ni: C, 50.30; H, 6.96. Found: C, 50.28; H, 6.71. 20 33 3 2 3.4. General Procedure for Synthesis of Complexes 2 and 3 To a solution of complex 1 (0.088 mmol) in CH Cl (10 mL), a solution of either 2 2 [Pb(SC F -4H) ] or [Pb(SC F ) ] (0.044 mmol) in acetone (20 mL) was added dropwise 6 4 2 6 5 2 under stirring. The resulting red-brick solution was stirred overnight. After this time the resulting reaction mixture was filtered through a short plug of Celite to remove the PbCl and the solvent was removed under vacuum and the residue recrystallized from CH Cl 2 2 affording in both cases yellow crystals, that were suitable for the X-ray diffraction analysis. 3.4.1. [Ni(SC F -4-H){C H -3-(C H O)-2,6-(OP Pr ) }] (2) 6 4 6 2 2 3 i 2 2 Yield: 93%, 0.051 g; m.p. 131–134 C. H NMR (300 MHz, CDCl ):  7.58 (d, 1H, J = 8.5 Hz), 6.65 (m, 1H), 6.46 (d, 1H, J = 8.5 Hz), 2.48 (s, 3H, CH ), 2.01–2.15 (m, 4H, H,H H,H 3 31 2 CH), 1.19–1.32 (m, 24H, CH ). P NMR (122 MHz, CDCl ):  194.21 (d, (AB) J = 293 Hz, 3 3 P,P 2 19 1P), 191.05 (d, (AB) J = 293 Hz, 1P). F NMR (283 MHz, CDCl ):  131.54–131.72 P,P 3 (m, o-F), 140.81–141.00 (m, m-F). MS (DART) m/z: 624 [(100%) M+H] . Anal. Calcd (%) for C H F NiO P S: C, 50.11; H, 5.50. Found: C, 50.13; H, 5.52. 26 34 4 3 2 3.4.2. [Ni(SC F ){C H -3-(C H O)-2,6-(OP Pr ) }] (3) 6 5 6 2 2 3 i 2 2 Yield: 90%, 0.050 g; m.p. 145–149 C. H NMR (300 MHz, CDCl ): 7.58 (d, 1H, J = 8.5 Hz), 6.46 (d, 1H, J = 8.5 Hz), 2.48 (s, 3H, CH ), 1.99–2.16 (m, 4H, CH), H,H H,H 3 31 2 1.13–1.36 (m, 24H, CH ). P NMR (122 MHz, CDCl ):  194.38 (d, (AB) J = 292 Hz, 1P), 3 3 P,P 2 19 191.22 (d, (AB) J = 292 Hz, 1P). F NMR (283 MHz, CDCl ):  130.99–131.16 (m, o-F), P,P 3 161.08–161.35 (m, p-F), 163.61–163.95 (m, m-F). MS (DART) m/z: 642 [(100%) M+H] . Anal. Calcd (%) for C H F NiO P S: C, 48.70; H, 5.19. Found: C, 48.69; H, 5.17. 26 33 5 3 2 3.5. Refinement Crystal data, data collection and structure refinement details are summarized in Table 1. Carbon-bound H atoms were positioned geometrically and included as riding atoms, with C–H = 0.98 Å with U (H) values of 1.5U (C) for methyl H, and C–H = 0.95 Å and 1.00 Å iso eq with U (H) values of 1.2 U (C) for methine. For more information about the structures of eq iso compounds 2 and 3, please refer to Supplementary Materials, as the picture shows 4. Conclusions Thus, in conclusion, we have provided a facile procedure for the synthesis of two Ni(II) pincer complexes including fluorinated thiolates on their structures. The complexes Molbank 2022, 2022, M1359 9 of 10 were fully characterized both in solution and solid state. Further analysis in the solid state revealed some interesting features that can be useful for the further development of these species and potential uses in catalysis, medicinal chemistry and materials sciences, some of these possibilities being currently explored in our laboratories. Supplementary Materials: The following supporting information can be downloaded. Supplemen- tary data for complexes (2) and (3) has been deposited at the Cambridge Crystallographic Data Centre. Copies of this information are available free of charge on request from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax: +44-1223-336033; e-mail deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk (accessed on 21 January 2022), quoting the deposition numbers CCDC 2142038-2142039. Author Contributions: Conceptualization, D.M.-M. and R.R.-M.; methodology, E.G.M.-E., R.R.-M., V.G.-B., J.M.G.-A. and N.O.-P.; software, N.O.-P., J.M.G.-A. and R.R.-M.; validation, D.M.-M., N.O.-P., J.M.G.-A. and R.R.-M.; formal analysis, D.M.-M., N.O.-P., J.M.G.-A. and R.R.-M.; investigation, E.G.M.-E., R.R.-M., V.G.-B. and N.O.-P.; resources, D.M.-M.; data curation, D.M.-M., R.R.-M. and E.G.M.-E.; writing—original draft preparation, D.M.-M., R.R.-M., E.G.M.-E., H.A.P.-C., L.A.M.-N.; writing—review and editing, D.M.-M. and R.R.-M.; visualization, N.O.-P. and R.R.-M.; supervision, D.M.-M. and R.R.-M.; project administration, D.M.-M.; funding acquisition, D.M.-M. All authors have read and agreed to the published version of the manuscript. Funding: Programa de Becas Posdoctorales-DGAPA-UNAM (Oficios: CJIC/CTIC/4064/2015 and CJIC/CTIC/4652/2016, respectively). CONACYT (grant NoA1-S-033933), PAPIIT (grant NoIN210520) and Subsecretaria de Eduacion Superior (PRODEP) grant OF-17-8204. Data Availability Statement: Not applicable. Acknowledgments: We would like to thank Simon Hernandez-Ortega, Chem. EngLuis Velasco Ibarra, Francisco Javier Pérez Flores, Q. Eréndira García Ríos, Lucia del Carmen Márquez Alonso, Lucero Ríos Ruiz, Alejandra Núñez Pineda (CCIQS), Q. María de la Paz Orta Pérez, Naytze Ortiz- Pastrana and Q. Roció Patiño-Maya for technical assistance. Conflicts of Interest: The authors declare no conflict of interest. Additionally, the funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the result. References 1. Morales-Morales, D. The chemistry of PCP pincer phosphinite transition metal complexes. In The Chemistry of the Pincer Compounds, 1st ed.; Morales-Morales, D., Jensen, C.M., Eds.; Elsevier: Amsterdam, The Netherlands, 2007; pp. 151–180. 2. Albrecht, M.; Morales-Morales, D. Pincer-Type Iridium Complexes for Organic Transformations. 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Journal

MolbankMultidisciplinary Digital Publishing Institute

Published: May 9, 2022

Keywords: crystal structure; fluorothiophenolate; POCOP ligand; pincer compounds; catalysis; catalyst

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