cis and trans influences on [Pt(SR_F)(triphos)]⁺ complexes (SR_F = polyfluorobenzothiolate)

Abstract

Platinum(II) derivatives of the tridentate ligand Ph₂PCH₂CH₂P(Ph)CH₂CH₂PPh₂ (triphos), including [Pt(SR_F)(triphos)](CF₃SO₃) R_F = C₆F₄CF₃-4 1, C₆F₅2, C₆HF₄-4 3, C₆H₄CF₃-4 4, C₆H₃F₂-2,4 5, C₆H₄F-2 6, C₆H₄F-4 7 and C₆H₅8, have been prepared and characterised. ¹H, ¹⁹F and ³¹P solution NMR has been used to evaluate the cis and trans influences of the fluorinated and non-fluorinated benzothiolate ligands, particularly through the cis and trans¹J_Pt–P values. The crystal and molecular structures of [Pt(SC₆F₄CF₃-4)(triphos)](CF₃SO₃) 1, with a perfluorinated thiolate ligand, [Pt(SC₆HF₄-4)(triphos)](CF₃SO₃) 3, having a fluorinated thiolate, and [Pt(SC₆H₅)(triphos)](CF₃SO₃) 8, bearing a non-fluorinated moiety, are discussed as examples of extreme electronegativities.

---

1. Introduction

A large number of studies focusing on trans and cis influences have been published from when they were first observed¹ up to the present day.²trans and cis influences have long been used to rationalise bond strengths and bond lengths and therefore reactivity,³ but their scope has been extended to include theoretical implications,⁴ the study of a growing number of ligands,⁵ their role in influencing the stability of geometrical isomers,⁶ and the particular chemical behaviours of specific processes, such as bond and molecule activation⁷ or ligand exchange.⁸ On the other hand, because the trans and cis influences also play significant roles in the chemistry of main group⁹ and rare earth elements,¹⁰ the general validity of these aspects is now well documented.

We have long-standing interest in transition metal derivatives bearing both phosphines and fluorinated benzothiolate ligands.¹¹ In particular, we are interested in the possible modulation of molecular properties induced by variations of the fluorination degree of benzothiolate ligands attached to the metal centre. If such a modulation is to be rationally achieved to some degree, a measure of the relative influence of each ligand is required. In this case, the modulated properties are the trans and cis influences.

To that end, we have examined the cis and trans influences of a series of fluorinated benzothiolate ligands (SR_F)⁻ in cationic complexes with the general formula [Pt(SR_F)(triphos)]⁺. PhP(CH₂CH₂PPh)₂ (triphos) has been widely studied¹² and is very useful for heteronuclear NMR studies because, once it is co-coordinated to platinum, this tridentate ligand allows the simultaneous observation of three ³¹P NMR coupling constants (¹J_Pt–Ptrans, ¹J_Pt–Pcis and ²J_{Ptrans–Pcis}).¹³ Furthermore, in square planar compounds, the tridentate ligand leaves just a single free and unique place of coordination to be occupied by the fluorothiolated ligands.

This work reports the synthesis of a new series of compounds with the general formula [Pt(SR_F)(triphos)](CF₃SO₃), R_F = C₆F₄CF₃-4 1, C₆F₅2, C₆HF₄-4 3, C₆H₄CF₃-4 4, C₆H₃F₂-2,4, 5, C₆H₄F-2 6, C₆H₄F-4 7 and C₆H₅8. The results show that there is a strengthening of the platinum–phosphorous bond trans to the thiolate as the number of fluorine atoms on this ligand increases.

2. Experimental

2.1. General

Solvents were dried using established procedures and were distilled under nitrogen gas immediately prior to use.²⁵ Thin-layer chromatography (TLC) (Merck, silica gel 60 F254 and neutral aluminium oxide 60 F254) was used to monitor the progress of the reactions being studied using hexane/ethyl acetate (9 : 1) as the eluent. All of the reactions were carried out under inert conditions with dry oxygen-free nitrogen gas using Schlenk techniques. Melting points were obtained using a Fisher-Johns melting point apparatus. Infrared spectra were recorded as KBr pellets on a Perkin Elmer Model 1605 Fourier spectrometer in the range of 4000 to 400 cm⁻¹. Elemental analyses were determined using a Fisons EA-1108 instrument. Nuclear magnetic resonance spectra, ¹H, ¹³C, ¹⁹F{¹H} and ³¹P{¹H}, were recorded on a Varian Unity INOVA-300 spectrometer. Chemical shifts are in ppm relative to internal TMS δ = 0 (¹H, ¹³C) and CFCl₃ (for ¹⁹F) and H₃PO₄ (for ³¹P) at 0 ppm as external references. J values are given in Hz. The following abbreviations were used for the multiplicities: s = singlet, bs = broad singlet, d = doublet, dd = doublets of doublets, t = triplet, and m = multiple. Positive-ion fast atom bombardment mass spectrometry (FAB⁺-MS) spectra were recorded on a Jeol JMS-SX102A mass spectrometer operated at an acceleration voltage of 10 kV. Samples were desorbed from a 3-nitrobenzyl alcohol matrix using 3 keV xenon atoms. Mass measurements in FAB are performed at a resolution of 3000 using magnetic field scans and the matrix ions as the reference material. Tl(CH₃COO), C₆H₅SH, C₆F₅SH and K₂[PtCl₄] were supplied by the Aldrich Co.; Ag(CF₃SO₃), Ph₂PC₂H₄P(Ph)C₂H₄PPh₂ and C₆HF₄SH were from Strem Chemicals; and 4-C₆F₄(CF₃)SH, 4-C₆H₄FSH, 4-C₆H₄(CF₃)SH and 2,4-C₆H₃F₂SH were acquired from Oakwood Products Inc. All of these chemicals were used without further purification. Tl(SR_F) (R_F = C₆F₄(CF₃)-4, C₆F₅, C₆HF₄-4, C₆H₄(CF₃)-4, C₆H₃F₂-2,4, C₆H₄F-2, C₆H₄F-4 and C₆H₅) salts were prepared by reacting stoichiometric quantities of the corresponding reactants (Tl(CH₃COO) + R_FSH) in water under vigorous stirring, filtering the precipitate and recrystallising the precipitate from acetone. [PtCl(triphos)]Cl (ref. 26) and [Pt(CF₃SO₃)(triphos)] (CF₃SO₃) (ref. 27) were prepared by published methods.

Caution: Tl(I) salts are known to be extremely toxic. All procedures were conducted in the fume cupboard and the collected Tl(I) halide was immediately oxidized with concentrated HNO₃.

2.2. Synthesis

Preparation of compounds 1 to 8. All of the reactions were carried out using stoichiometric quantities of the reactants, and because all of the preparations were similar, only a typical procedure is described below. In a 50 mL round bottom flask, one equivalent of the corresponding thallium salt, Tl(SR_F) (ca. 45.3 mg, 0.1 mmol for R = C₆F₄CF₃) in 10 mL of dichloromethane and a solution of one equivalent of [Pt(CF₃SO₃)(triphos)](CF₃SO₃) (ca. 103.0 mg, 0.1 mmol) in 25 mL of dichloromethane were mixed under vigorous stirring. After 24 h, the yellow solution was filtered off to obtain white TlCl solid. The clear yellow solution was evaporated over a period of ca. 24 h to obtain yellow crystalline solids formulated as [Pt(SR_F)(triphos)](CF₃SO₃).
[Pt(SC₆F₄CF₃-4)(triphos)](CF₃SO₃) 1. White crystalline solid; 95.7% yield; mp: 110–111 °C; Anal. calcd for C₄₂H₃₃O₃F₁₀S₂P₃Pt: C: 44.7, H: 2.94, S: 5.68, found C: 44.7, H: 2.9, S: 5.7; IR (KBr): ν = 3056, 2920, 1641, 1473, 1437, 1324, 1260, 1141, 1029, 972 cm⁻¹; MS-FAB⁺ (m/z): 978 [M]⁺ (100); NMR ³¹P{¹H} (121.3 MHz, CDCl₃): 89.9 (d, P_trans, ¹J_Ptrans–Pt = 2524 Hz), 40.0 (d, P_cis, ¹J_Pcis–Pt = 2519 Hz, ²J_{Ptrans–Pcis} = 2.9 Hz); NMR ¹⁹F{¹H} (282 MHz, CDCl₃): −82.9 (s, 3F, CF₃SO₃), −136.30 (m, 2F, o-F), −147.28 (m, 2F, m-F), −60.4 (t, 3F, CF₃, ⁴J_F–F = 21.1 Hz); NMR ¹H (300 MHz, CDCl₃): 2.1–3.9 (m, 8H, CH₂–CH₂ triphos), 7.2–8.1 (m, 25H, Ph triphos).
[Pt(SC₆F₅)(triphos)](CF₃SO₃) 2. White crystalline solid; 98.3% yield; mp: d-195 °C; Anal. calcd for C₄₁H₃₃O₃F₈S₂P₃Pt C: 45.68, H: 3.08, S: 5.94, found C: 45.7, H: 3.0, S: 5.9; IR (KBr): ν = 3055, 2918, 1625, 1573, 1508, 1478, 1274, 1151, 1030, 857 cm⁻¹; MS-FAB⁺ (m/z): 928 [M]⁺ (100), 409 (M⁺-SR_F-(PPh₂)₂-(CH₂)₂). NMR ³¹P{¹H} (121.3 MHz, CDCl₃): 88.9 (d, P_trans, ¹J_Ptrans–Pt = 2466 Hz), 41.2 (d, P_cis, ¹J_Pcis–Pt = 2551 Hz; ²J_{Ptrans–Pcis} = 4.0 Hz). NMR ¹⁹F{¹H} (282 MHz, CDCl₃): −78.67 (s, 3F, CF₃SO₃), −132.34 (m, 2F, o-F), −163.1 (m, 2F, m-F), −159.7 (m, 1F, p-F). NMR ¹H (300 MHz, CDCl₃): 2.1–3.9 (m, 8H, CH₂–CH₂ triphos), 7.2–8.1 (m, 25H, Ph triphos).
[Pt(SC₆HF₄-4)(triphos)](CF₃SO₃) 3. White crystalline solid, 74.5% yield, mp: 244–245 °C. Anal. calcd for C₄₁H₃₄O₃S₂F₇P₃Pt C: 46.0, H: 3.3, S: 6.1. Found C: 46.5, H: 3.2, S: 6.0. IR (KBr): ν = 3055, 2920, 1625, 1482, 1436, 1262, 1151, 1030, 910 cm⁻¹; MS-FAB⁺ (m/z): 910 [M]⁺ (100). NMR ³¹P{¹H} (121.3 MHz, CDCl₃): 89.0 (d, P_trans, ¹J_Ptrans–Pt = 2465 Hz), 40.1 (d, P_cis, ¹J_Pcis–Pt = 2550 Hz; ²J_{Ptrans–Pcis} = 4.1 Hz). NMR ¹⁹F (282 MHz, CDCl₃): −78.77 (s, 3F, CF₃SO₃), −132.9 (m, 2F, m-F), −140.4 (m, 2F, o-F). NMR ¹H (300 MHz, CDCl₃): 6.22 (tt, 1H p-H), 2.1–3.9 (m, 8H, CH₂–CH₂ triphos), 7.2–8.1 (m, 25H, Ph triphos).
[Pt(SC₆H₄(CF₃)-4)(triphos)](CF₃SO₃) 4. Yellow crystalline solid, 62.01% yield, mp: 90–91 °C. Anal. calcd for C₄₂H₃₇O₃S₂F₆P₃Pt, C: 47.7, H: 3.53, S: 6.0. Found C: 47.8, H: 3.5, S: 6.1. IR (KBr): ν = 3054, 2920, 1598, 1436, 1323, 1262, 1154, 1102, 1029, 831 cm⁻¹; MS-FAB⁺ (m/z): 907 [M]⁺ (100). NMR ³¹P{¹H} (121.3 MHz, CDCl₃): δ = 89.1 (d, P_trans, ¹J_Ptrans–Pt = 2370 Hz), 41.0 (d, P_cis, ¹J_Pcis–Pt = 2566 Hz; ²J_{Ptrans–Pcis} = 4.4 Hz). NMR ¹⁹F (282 MHz, CDCl₃): δ = −78.66 (s, 3F, CF₃SO₃), −62.20 (s, 3F, CF₃). NMR ¹H (300 MHz, CDCl₃): δ = 6.84 (d, 2H, o-H), 6.6 (d, 2H, m-H, ³J_H–H = 8.1 Hz), 2.1–3.9 (m, 8H, CH₂–CH₂ triphos), 7.2–8.1 (m, 25H, Ph triphos).
[Pt(SC₆H₃F₂-2,4)(triphos)](CF₃SO₃) 5. Yellow crystalline solid, 82.45% yield, mp: 108–109 °C. Anal. calcd for C₄₁H₃₆O₃S₂F₅P₃Pt, C: 48.9, H: 3.54, S: 6.26. Found C: 49.0, H: 3.7, S: 6.4. IR (KBr): ν = 3053, 2916, 1587, 1476, 1436, 1260, 1151, 1029, 961 cm⁻¹. MS-FAB⁺ (m/z): 874 [M]⁺ (100). NMR ³¹P{¹H} (121.3 MHz, CDCl₃): δ = 88.1 (d, P_trans, ¹J_Ptrans–Pt = 2354 Hz), 41.4 (d, P_cis, ¹J_Pcis–Pt = 2599 Hz; ²J_{Ptrans–Pcis} = 4.9 Hz). NMR ¹⁹F (282 MHz, CDCl₃): δ = −78.75 (s, 3F, CF₃SO₃), −100.42 (m, 1F, o-F), −114.69 (m, 1F, p-F). NMR ¹H (300 MHz, CDCl₃): δ = 6.84 (m, 1H, H-3), 6.1 (m, 1H, H-5), 5.9 (m, 1H, H-6), 2.1–3.9 (m, 8H, CH₂–CH₂ triphos), 7.2–8.1 (m, 25H, Ph triphos).
[Pt(SC₆H₄F-2)(triphos)](CF₃SO₃) 6. Yellow crystalline solid, 75.25% yield, mp: d-198 °C. Anal. calcd for C₄₁H₃₇O₃S₂F₄P₃Pt, C: 48.9, H: 3.7, S: 6.3. Found C: 49.0, H: 3.7, S: 6.4. IR(KBr): ν =3051, 2917, 1571, 1467, 1436, 1278, 1255, 1221, 1151, 1106, 1027, 998, 732, 750, 722, 706, 693, 636, 519 cm⁻¹. MS-FAB⁺ (m/z): 856 [M]⁺ (100), 407 (M⁺-SR_F-(PPh₂)₂-(CH₂)₂). NMR ³¹P{¹H} (121.3 MHz, CDCl₃): δ = 86.5 (d, P_trans, ¹J_Ptrans–Pt = 2354 Hz), 39.7 (d, P_cis, ¹J_Pcis–Pt = 2591 Hz; ²J_{Ptrans–Pcis} = 4.7 Hz). NMR ¹⁹F (282 MHz, CDCl₃): δ = −82.0 (s, 3F, CF₃SO₃), −108.32 (m, 1F, o-F). NMR ¹H (300 MHz, CDCl₃): δ = 6.9 (m, 1H, H-3), 6.5 (m, 1H, H-4), 6.2 (m, 1H, H-6), 6.34 (m, 1H, H-5), 2.1–3.9 (m, 8H, CH₂–CH₂ triphos), 7.2–8.1 (m, 25H, Ph triphos).
[Pt(SC₆H₄F-4)(triphos)](CF₃SO₃) 7. Yellow crystalline solid, 89.97% yield, mp: 105–108 °C. Anal. calcd for C₄₁H₃₇O₃S₂F₄P₃Pt, C: 48.9, H: 3.7, S: 6.3. Found C: 49.0, H: 3.7, S: 6.4. IR (KBr): ν = 3053, 2917, 1629, 1584, 1481, 1436, 1263, 1151, 1029, 829 cm⁻¹. MS-FAB⁺ (m/z): 856 [M]⁺ (100), 729 [M]⁺-SR_F (20). NMR ³¹P{¹H} (121.3 MHz, CDCl₃): δ = 87.7 (d, P_trans, ¹J_Ptrans–Pt = 2313 Hz), 41.8 (d, P_cis, ¹J_Pcis–Pt = 2613 Hz; ²J_{Ptrans–Pcis} = 5.3 Hz). NMR ¹⁹F (282 MHz, CDCl₃): δ = −82.0 (s, 3F, CF₃SO₃), −108.3 (m, 1F, p-F). NMR ¹H (300 MHz, CDCl₃): δ = 6.73 (m, 2H, o-H), 6.12 (m, 2H, m-H), 2.1–3.9 (m, 8H, CH₂–CH₂ triphos), 7.2–8.1 (m, 25H, Ph triphos).
[Pt(SC₆H₅)(triphos)](CF₃SO₃) 8. Yellow crystalline solid, 97.37% yield, mp: 234–235 °C. Anal. Calcd for C₄₁H₃₈O₃S₂P₃F₃Pt, C: 49.8, H: 3.87, S: 6.49. Found C: 49.8, H: 3.9, S: 6.5. IR(KBr): ν = 3052, 2922, 1575, 1471, 1435, 1271, 1147, 1029 cm⁻¹. MS-FAB⁺ (m/z): 838 [M]⁺ (100), 729 [M]⁺-SR_F (20). NMR ³¹P{¹H} (121.3 MHz, CDCl₃): δ = 87.5 (d, P_trans, ¹J_Ptrans–Pt = 2306 Hz), 41.6 (d, P_cis, ¹J_Pcis–Pt = 2609 Hz; ²J_{Ptrans–Pcis} = 5.2 Hz). NMR ¹⁹F (282 MHz, CDCl₃): δ = −78.78 (s, 3F, CF₃SO₃). NMR ¹H (300 MHz, CDCl₃): δ = 6.80 (m, 2H, o-H), 6.59 (m, 1H, p-H), 6.46 (m, 2H, m-H), 2.1–3.2 (m, 8H, CH₂–CH₂ triphos), 7.3–8.1 (m, 25H, Ph triphos).

2.3. X-Ray crystal structure determination

Suitable crystals for X-ray diffraction analyses of compounds 1, 3 and 8 were grown by slow (multiday) solvent evaporation of a concentrated acetone solution at room temperature (293–298 K). Crystals were mounted on a glass fiber. A full hemisphere of data was collected with 30 s frames using an Enraf-Nonius Kappa diffractometer fitted with a CCD based detector using MoK_α radiation (0.71073 Å). Diffraction data and unit-cell parameters were consistent with the assigned space groups. The structures were solved by direct methods, completed by subsequent Fourier syntheses and refined with full-matrix least-squares methods against |F²| data. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were treated as idealized contributions. Scattering factors and anomalous dispersion coefficients are contained in the SHELXTL 5.03 program library.²⁸ Ball-and-stick and space-filling diagrams were prepared using DIAMOND.²⁹

Crystal structure data for [Pt(SC₆F₄CF₃-4)((C₆H₅)₂PC₂H₄P(C₆H₅)C₂H₄P(C₆H₅)₂)](CF₃SO₃) 1. C₄₂H₃₃F₁₀O₃P₃PtS₂, M = 1127.80, triclinic, a = 11.1223(4) Å, b = 13.6579(6) Å, c = 16.7386(7) Å, α = 67.229(3)°, β = 81.640(2)°, γ = 71.075(2)°, V = 2217.22(16) ų, T = 293(2) K, space group P1̄, Z = 2, μ(MoKα) = 3.447 mm⁻¹, 11 281 reflections measured, 6966 independent reflections (R_int = 0.0381). The final R₁ values were 0.0866 (I > 2σ(I)). The final wR(F²) values were 0.2318 (I > 2σ(I)). The final R₁ values were 0.1128 (all data). The final wR(F²) values were 0.2972 (all data). The goodness of fit on F² was 1.335. CCDC 1025112.

Crystal structure data for [Pt(SC₆HF₄-4)((C₆H₅)₂PC₂H₄P(C₆H₅)C₂H₄P(C₆H₅)₂)](CF₃SO₃) 3. C₄₁H₃₄F₇O₃P₃PtS₂, M = 1059.80, monoclinic, a = 10.188(2) Å, b = 19.711(4) Å, c = 21.039(4) Å, β = 96.02(3)°, V = 4201.8(14) ų, T = 293(2) K, space group P2₁/n, Z = 4, μ(MoKα) = 3.622 mm⁻¹, 16 857 reflections measured, 5642 independent reflections (R_int = 0.0950). The final R₁ values were 0.0724 (I > 2σ(I)). The final wR(F²) values were 0.1729 (I > 2σ(I)). The final R₁ values were 0.1537 (all data). The final wR(F²) values were 0.2359 (all data). The goodness of fit on F² was 1.037. CCDC 1026048.

Crystal structure data for [Pt(SC₆H₅)((C₆H₅)₂PC₂H₄P(C₆H₅)C₂H₄P(C₆H₅)₂)](CF₃SO₃) 8. C₄₁H₃₈F₃O₃P₃PtS₂, M = 987.83, monoclinic, a = 10.2751(3) Å, b = 19.9018(7) Å, c = 19.3686(8) Å, β = 93.7440(10)°, V = 3952.3(2) ų, T = 293(2) K, space group P2₁/n, Z = 4, μ(MoKα) = 3.830 mm⁻¹, 13 735 reflections measured, 6381 independent reflections (R_int = 0.0790). The final R₁ values were 0.0660 (I > 2σ(I)). The final wR(F²) values were 0.1774 (I > 2σ(I)). The final R₁ values were 0.1106 (all data). The final wR(F²) values were 0.2267 (all data). The goodness of fit on F² was 1.066. CCDC 1025113.

3. Results and discussion

3.1. Synthesis of Pt(II) complexes 1–8

[Pt(SR_F)(triphos)](CF₃SO₃) square planar thiolate platinum(II) complexes 1 to 8 (triphos = PhP(CH₂CH₂PPh₂)₂; R_F = C₆F₄CF₃-4 1, C₆F₅2, C₆HF₄-4 3, C₆H₄CF₃-4 4, C₆H₄F₂-2,4 5, C₆H₄F-2 6, C₆H₄F-4 7 and C₆H₅8) were synthesized by metathesis reactions, in a 1 : 1 stoichiometry, between [Pt(CF₃SO₃)(triphos)](CF₃SO₃) and the corresponding thallium thiolate salts, Tl(SR_F). They were all isolated as white or yellow solids, which were relatively soluble in acetone, acetonitrile and dimethylsulfoxide. Compounds 1–8 are inert to oxidation in an open atmosphere over a period of weeks.

¹H, ¹⁹F and ³¹P NMR, FAB⁺ mass spectrometry, elemental analyses and vibrational spectra described in the experimental section have been used to characterise the prepared complexes.

3.2. Solid-state molecular structures of [Pt(SC₆F₄CF₃-4)(triphos)][OTf] 1, [Pt(SC₆HF₄-4)(triphos)][OTf] 3 and [Pt(SC₆H₅)(triphos)][OTf] 8

Moderate-quality crystals for X-ray diffraction analysis of complexes [Pt(SC₆F₄CF₃-4)(triphos)](CF₃SO₃) 1, [Pt(SC₆HF₄-4)(triphos)](CF₃SO₃) 3 and [Pt(SC₆H₅)(triphos)](CF₃SO₃) 8 were obtained by slow evaporation of concentrated acetone solutions at room temperature (293–298 K). The molecular structure in the solid state of compounds 1, 3 and 8 with their respective numbering schemes is depicted in Fig. 1 to 3. Selected bond lengths (Å) and angles (°) are summarized in Table 1.

Fig. 1 Ball and stick and space-filling representations with the numbering scheme of the molecular structure of [Pt(SC₆F₄CF₃-4)(triphos)](CF₃SO₃) 1 determined by single crystal X-ray diffraction. Pt = gray, P = pink, S = yellow, C = black, F = green, H = white. The counterion has been omitted for clarity.

Fig. 2 Ball and stick and space-filling representations with the numbering scheme of the molecular structure of [Pt(SC₆HF₄-4)(triphos)](CF₃SO₃) 3 determined by single crystal X-ray diffraction. Pt = gray, P = pink, S = yellow, C = black, F = green, H = white. The counterion has been omitted for clarity.

Fig. 3 Ball and stick and space-filling representations with the numbering scheme of the molecular structure of [Pt(SC₆H₅)(triphos)](CF₃SO₃) 8 determined by single crystal X-ray diffraction. Pt = gray, P = pink, S = yellow, C = black, H = white. The counterion has been omitted for clarity.

Table 1 Selected bond lengths (Å) and angles (°) for compounds 1, 3 and 8

	1	3	8
Bond length (Å)
Pt1–S1	2.354(3)	2.343(5)	2.349(6)
Pt1–P1	2.325(4)	2.313(5)	2.295(3)
Pt1–P2	2.239(3)	2.234(4)	2.237(3)
Pt1–P3	2.292(4)	2.308(4)	2.331(3)
Angles (°)
P1–Pt1–S1	102.9(1)	104.3(2)	88.0(2)
P1–Pt1–P2	84.4(1)	83.4(2)	83.9(1)
P2–Pt1–P3	82.6(1)	83.9(2)	83.9(1)
P3–Pt1–S1	90.2(2)	88.8(2)	105.1(2)
P2–Pt1–S1	172.7(1)	172.1(1)	168.6(2)
Pt1–S1–C1	109(1)	115(1)	88.0(2)

---

For the three molecular structures, platinum(II) lies at the centre of a distorted square-planar geometry with the triphos ligand coordinated in a tridentate fashion forming two five-membered rings. All platinum–phosphorous bond lengths and angles are in agreement with previously reported values.^14–16 The Pt1–P2 bond is shorter than the two mutually trans platinum–phosphorous bonds due to the double chelate effect, in agreement with previously reported chloride complexes [PtCl(triphos)]X (X = Cl⁻ or CuCl₂⁻).^13a The thiolate ligand, SR_F⁻, occupies the platinum fourth coordination site with the expected bond lengths and angles for platinum–thiolate complexes.^17–21

[Pt(SC₆F₄CF₃-4)(triphos)][OTf] 1. Isolated crystals belong to the triclinic space group P1̄. There is a complete platinum complex monocation and one trifluoromethanesulfonate anion in the asymmetric unit; both trifluoromethyl groups on the structure are disordered. The electron-deficient character of the perfluorinated aromatic ring of the thiolate ligand SC₆F₄CF₃-4 induces an aromatic interaction²² with one of the electron-rich phenyl rings of the triphos ligand with an interplanar distance of 3.6 Å between centroids of both rings, which is not observed in the non-fluorinated complex 8 (vide infra).

[Pt(SC₆HF₄-4)(triphos)][OTf] 3. The analyzed crystal belongs to the monoclinic space group P2₁/n. The asymmetric unit consists of a complete platinum complex and a trifluoromethanesulfonate anion. The SC₆F₄H-4 thiolate ring also forms an aromatic interaction with one of the electron-rich phenyl rings of the triphos ligand with an interplanar distance of 3.7 Å, slightly larger than the one observed for the extremely electron-poor SC₆F₅CF₃-4 thiolate in complex 1.

[Pt(SC₆H₅)(triphos)][OTf] 8. Isolated crystals belong to the monoclinic space group P2₁/n. A complete platinum complex and a trifluoromethanesulfonate anion are present in the asymmetric unit. The carbon atoms on the thiolate phenyl ring were refined isotropically. In clear contrast to the molecular structures of complexes 1 and 3, all the aromatic rings distribute uniformly in the space to minimize electrostatic repulsion between them.

It is clear that there is no significant difference in the Pt–P2 bond distance (P_trans to the thiolate ligand) for the three complexes. Bond lengths in similar complexes that have phosphorus and sulphur ligands trans to each other are those of cis-[Pt(SPh)(PhSCSO)(PPh₃)₂] (2.287(3) Å),^20a [Pt(SPh)₂(Ph₂CH=CHPPh₂)] (Pt(1)–P(1) 2.2362(18) Å and Pt(1)–P(2) 2.2462(18) Å)^20b and [Pt(SPh)₂(dppf)] (dppf = Fe(η⁵-C₅H₄PPh₂)₂, Pt1–P1 2.313(1) Å and Pt1–P2 2.294(1) Å).^20c

This is an unexpected result because the ¹J_Pt–Ptrans is very different between them (vide infra) and therefore this similarity in bond lengths probably reflects factors such steric hindrances, crystal packing and the restraints imposed by the double-chelating triphos ligand which are not present in solution.

3.3. Solution nuclear magnetic resonance

In terms of nuclear magnetic resonance, the magnetic systems corresponding to each of the fluorinated rings included in this work are p-C₆F₄(CF₃) and p-C₆H₄(CF₃) AA′BB′X₃; C₆F₅, and C₆H₅ AA′BB′C; p-C₆F₄H and p-C₆H₄F AA′BB′X; and 2,4-C₆H₄F₂ ABCXY. The ¹H and ¹⁹F NMR parameters for compounds 1 to 8 are listed in the experimental section.

As expected, the ³¹P{¹H} NMR spectra of compounds 1 to 8 reflect the square planar structures of these complexes and exhibit one resonance arising from the two phosphorus nuclei in the trans positions and one signal due to the third phosphorus atom trans to the thiolate ligand. The relative ratio of these signals is 2 : 1, respectively, and both have platinum satellites due to coupling to ¹⁹⁵Pt (33% natural abundance).

Some phosphorus–phosphorus magnetic couplings are unobservable, but this is expected for square-planar triphos derivatives with all of the phosphorus atoms coordinated to the same metal centre. The range of chemical shifts for the phosphorus atoms in cis and trans positions is very narrow, 39.7–41.8 and 89.9–86.5 ppm, respectively. The NMR parameters for compounds 1 to 8 are collected in Table 2.

Table 2 ³¹P chemical shifts (ppm) and coupling constants (Hz) for compounds [Pt(SR_F)(triphos)]⁺1 to 8 and selected examples of published parameters for [PtX(triphos)]⁺ compounds

Compound		δ ^31Pcis ppm	δ ^31Ptrans ppm	^1 J Pt–Pcis Hz	^1 J Pt–Ptrans Hz	^2 J Pcis–Ptrans Hz
[Pt(SC6F4(CF3-4))(triphos)]^+	1	40.0	89.9	2519	2524	2.9
[Pt(SC6F5)(triphos)]^+	2	41.2	88.9	2551	2466	4.0
[Pt(SC6HF4-4)(triphos)]^+	3	41.0	89.0	2550	2465	4.1
[Pt(SC6H4(CF3)-4)(triphos)]^+	4	41.0	89.1	2566	2370	4.4
[Pt(SC6H3F2-2,4)(triphos)]^+	5	41.4	88.0	2599	2354	4.9
[Pt(SC6H4F-2)(triphos)]^+	6	39.7	86.5	2591	2354	4.7
[Pt(SC6H4F-4)(triphos)]^+	7	41.8	87.7	2613	2313	5.3
[Pt(SC6H5)(triphos)]^+	8	41.6	87.5	2609	2306	5.2
[Pt(OTf)(triphos)]^+^12c				2513	3314
[PtCl(triphos)]^+^12c				2451	3080
[Pt(SnR)(triphos)]^+^12c				2323	2433
[PtCl(triphos)]^+^12d				2456	3065
[Pt(SCN)(triphos)]^+^12d				2442	3049
[PtBr(triphos)]^+^12d				2449	3016
[PtI(triphos)]^+^12d				2417	2902
[Pt(NCS)(triphos)]^+^12d				2445	2725
[Pt(CN)(triphos)]^+^12d				2373	2216
[Pt(SMe)(triphos)]^+^12d				2639	2190
[Pt(Me)(triphos)]^+^12d				2745	1521

---

Platinum–phosphorous coupling constants show differences of up to ca. 94 Hz for the cis configuration and much larger differences of up to ca. 217 Hz for the trans arrangement. The magnitude of the coupling constant ¹J_Pt–Pcis decreases with a decrease in the degree of fluorination of the ring, from 2519 Hz when R_F = C₆F₄(CF₃) to 2608 Hz when R_F = C₆H₅. In contrast, ¹J_Pt–Ptrans follows the opposite trend and goes from 2523 Hz when R_F = C₆F₄(CF₃) to 2313 Hz when R_F = C₆H₅, reflecting the cis and trans influences on the order of this series.

Several correlations of the NMR data are found. For example, the linear relationship between ¹J_Pt–Ptrans and ²J_{Ptrans–Pcis} is shown in Fig. 4.

Fig. 4 Linear relationship between ¹J_Pt–Ptrans and ²J_{Pcis–Ptrans} for compounds 1 to 8. ¹J_Pt–Ptrans = −95.567(²J_{Ptrans–Pcis}) + 2817.3 with R² = 0.9408.

As an additional element, the Mulliken charge on each sulphur atom in the corresponding free thiol (calculated by the non-geometrical restricted optimisation of the structure using Gaussian 03W²³) is shown in Fig. 5 plotted against the ¹J_Pt–Ptrans for the corresponding compound. Although this basic calculation level accounts for the electronic effects on single molecules, there is a remarkable linear correlation for compounds 1 to 8 with the presumably more electronegative ligands having the more positively charged sulphur atoms.

Fig. 5 Mulliken S atom charge on the free thiols versus the ¹J_Pt–Ptrans for compounds 1 to 8. ¹J_Pt–Ptrans = 1233.1(Mulliken S charge) + 2117.2 with R² = 0.9655.

As suggested by the NMR data, the proposed order of the trans influence (decreasing ¹J_Pt–Ptrans coupling constants, increasing the trans influence) is SC₆F₄CF₃-4 < SC₆F₅ ≈ SC₆HF₄-4 < SC₆F₄CF₃ < SC₆H₃F₂-2,4 < SC₆H₄F-2 ≈ SC₆H₄F-4 < SC₆H₅. The thiolate ligand series should be put in place of the SPh ligand of the following sequence of the strength of the trans influence suggested from a very sound study of this parameter: Ph > Me > SPh > SePh > NO₂ > I > N₃> Br > Cl > AcO > CF₃COO > F > NO₃.²⁴

4. Conclusions

In this paper, we analysed the relationship between the nature of a series of polyfluorinated thiolates (SR_F) and the ³¹P NMR-derived cis and trans influences on the (SR_F)–Pt–(triphos) coordination system.

The direct relationship between the magnitude of the coupling constants ¹J_Pt–Pcis and ¹J_Pt–Ptrans and the platinum–phosphorus bond energy is now well established, and according to the magnitude of the coupling constants, it was found that both the cis and trans influences of the SR_F ligands follow the same order, i.e., SC₆F₄CF₃-4 < SC₆F₅ ≈ SC₆HF₄-4 < SC₆F₄CF₃ < SC₆H₃F₂-2,4 < SC₆H₄F-2 ≈ SC₆H₄F-4 < SC₆H₅.

In addition, Fig. 4 shows the relationship between the cis and trans coupling constants and the corresponding chemical shifts, which show that in this series, both effects are well detected and follow the same order.

The bond lengths found for Pt–P_trans when the opposite ligands are SC₆F₄CF₃-4, SC₆HF₄-4 and SC₆H₅ are practically identical, and therefore, in our case, the crystallographic evidence does not show a significant difference in the trans influence of these ligands.

Acknowledgements

This work was supported by CONACYT (Project CB-2012-177498) and DGAPA-UNAM (Project IN-202314). We thank Mr Esteban Padilla Mata for experimental assistance.

References

1. (a) A. Pidcock, R. E. Richards and L. M. Venanzi, J. Chem. Soc. A, 1966, 1007–1710; (b) L. M. Venanzi, Chem. Br., 1968, 4, 162–167; (c) G. B. Kauffman, J. Chem. Educ., 1977, 54, 86–89.
2. (a) A. O. Ogweno, S. O. Ojwach and M. P. Akerman, Dalton Trans., 2014, 43, 1228–1237; (b) J. Olguín, H. Müller-Bunz and M. Albrecht, Chem. Commun., 2014, 50, 3488–3490; (c) D. Mendola, N. Saleh, N. Vanthuyne, C. Roussel, L. Toupet, F. Castiglione, T. Caronna, A. Mele and J. Crassous, Angew. Chem., Int. Ed., 2014, 53, 5786–5790; (d) X. Xu, B. Pooi, H. Hirao and S. H. Hong, Angew. Chem., Int. Ed., 2014, 53, 1283–1287.
3. (a) J. E. Wheatley, C. A. Ohlin and A. B. Chaplin, Chem. Commun., 2014, 50, 685–687; (b) L. Rigamonti, M. Rusconi, A. Forni and A. Pasini, Dalton Trans., 2011, 40, 10162–10173.
4. A. Stirling, N. N. Nair, A. Lledós and G. Ujaque, Chem. Soc. Rev., 2014, 43, 4940–4952.
5. (a) Z. W. Lai, R. F. Yang, K. Y. Ye and H. Sun, Beilstein J. Org. Chem., 2014, 10, 1261–1266; (b) K. A. Netland, A. Krivokapic and M. Tilset, J. Coord. Chem., 2010, 63, 2909–2927; (c) J. A. Dimmer, H. Schubert and L. Wassermann, Chem. – Eur. J., 2009, 15, 10613–10619.
6. (a) O. O. Lubimova and O. V. Sizova, Russ. J. Coord. Chem., 2005, 31, 575–579; (b) J. N. Harvey, K. M. Heslop, A. G. Orpen and P. G. Pringle, Chem. Commun., 2003, 278–279; (c) G. K. Anderson and R. J. Cross, Chem. Soc. Rev., 1980, 9, 185–215; (d) B. C. Sanders, S. M. Hassan and T. C. Harrop, J. Am. Chem. Soc., 2014, 136, 10230–10233.
7. (a) H. Kondo, F. Yu, J. Yamaguchi, G. Liu and K. Itami, Org. Lett., 2014, 16, 4212–4215; (b) L. T. Haar, K. P. Jensen, J. Boesen and H. E. M. Christensen, J. Inorg. Biochem., 2010, 104, 136–145; (c) H. J. Zhu and T. Ziegler, Organometallics, 2008, 27, 1743–1749.
8. J. Goodman, V. V. Grushin, R. B. Larichev, S. A. MacGregor, W. J. Marshall and D. C. Roe, J. Am. Chem. Soc., 2010, 132, 12013–12026.
9. (a) M. Ochiai, T. Sueda, K. Miyamoto, P. Kiprof and V. V. Zhdankin, Angew. Chem., 2006, 118, 8383–8386; (b) P. K. Sajith and C. H. Suresh, Inorg. Chem., 2011, 50, 8085–8093.
10. (a) K. Krogh-Jespersen, M. D. Romanelli, J. H. Melman, T. J. Emge and J. G. Brennan, Inorg. Chem., 2010, 49, 552–560; (b) T. J. Emge, A. Komienko and J. G. Brennan, Acta Crystallogr., Sect. C: Cryst. Struct. Commun., 2009, 65, m422–m425; (c) E. Lu, O. J. Cooper, J. McMaster and F. Tuna, Angew. Chem., Int. Ed., 2014, 53, 6696–6700; (d) A. J. Lewis, K. C. Mullane and E. Nakamaru-Ogiso, Inorg. Chem., 2014, 53, 6944–6953.
11. (a) G. Rivera, S. Bernès, C. Rodríguez de Barbarín and H. Torrens, Inorg. Chim. Acta, 2009, 362, 5122–5125; (b) L. Villanueva, M. Arroyo, S. Bernès and H. Torrens, Chem. Commun., 2004, 1942–1943; (c) G. Rivera, S. Bernés and H. Torrens, Polyhedron, 2007, 26, 4276–4286; (d) S. E. Castillo-Blum, M. Flores-Alamo, D. Franco-Bodek, G. Hernandez and H. Torrens, Inorg. Chem. Commun., 2014, 45, 44–47; (e) J. Tiburcio, S. Bernès and H. Torrens, Polyhedron, 2006, 25, 1549–1554.
12. (a) A. Ienco, S. Midollini, A. Orlandini and A. Vacca, Inorg. Chim. Acta, 2004, 357, 2615–2623; (b) M. I. Garcıá-Seijo, A. Castiñeiras, B. Mahieu, L. Janosic, Z. Berente, L. Kollar and M. E. Garcıa-Fernandez, Polyhedron, 2001, 20, 855–868; (c) T. Marx and L. Wesemann, J. Organomet. Chem., 2000, 614–615, 137–143; (d) G. Annibale, P. Bergamini, V. Bertolasi, M. Cattabriga and V. Ferretti, Inorg. Chem. Commun., 2000, 3, 303–306; (e) G. Annibale, P. Bergamini and M. Cattabriga, Inorg. Chim. Acta, 2001, 316, 25–32; (f) D. Fernandez, P. Sevillano, M. I. García-Seijo, A. Castiñeiras, L. Janosi, Z. Berente, L. Kollar and M. E. García-Fernandez, Inorg. Chim. Acta, 2001, 312, 40–52.
13. (a) D. Fernandez, M. I. García-Seijo, P. Sevillano, A. Castiñeiras and M. E. García-Fernandez, Inorg. Chim. Acta, 2005, 358, 2575–2584; (b) G. Petocz, L. Janosi, W. Weissensteiner, Z. Csok, Z. Berente and L. Kollar, Inorg. Chim. Acta, 2000, 303, 300–305; (c) M. Bortoluzzi, G. Annibale, G. Marangoni, G. Paolucci and B. Pitteri, Polyhedron, 2006, 25, 1979–1984.
14. F. A. Cotton and B. Hong, Polydentate Phosphines: Their Syntheses, Structural Aspects, and Selected Applications, Prog. Inorg. Chem., 1992, 40, 179.
15. P. Sevillano, A. Habtemariam, S. Parsons, A. Castiñeiras, M. E. García and P. J. Sadler, J. Chem. Soc., Dalton Trans., 1999, 2861–2870.
16. H. Braunschweig, K. Radacki and A. Schneider, Science, 2010, 328, 345–347.
17. G. Rivera, H. Torrens and S. Bernes, Acta Crystallogr., Sect. E: Struct. Rep. Online, 2006, E62, m3287–m3288.
18. G. Rivera, S. Bernes, C. Rodriguez de Barbarin and H. Torrens, Inorg. Chem., 2001, 40, 5575–5580.
19. S. E. Castillo-Blum, M. Flores-Alamo, D. Franco-Bodek, G. Hernandez and H. Torrens, Inorg. Chem. Commun., 2014, 45, 44–47.
20. (a) J. W. Gosselink, G. van Koten, A. M. F. Brouwers and O. K. Overbeek, J. Chem. Soc., Dalton Trans., 1981, 242–252; (b) R. H. Vaza, R. M. Silvaa, J. H. Reibenspiesb and O. A. Serra, J. Braz. Chem. Soc., 2002, 13, 82–87; (c) W. S. Han, Y.-J. Kim and S. W. Lee, Bull. Korean Chem. Soc., 2003, 24, 60–64; (d) M. D. Rudd and J. C. Jeffery, Inorg. Chim. Acta, 2007, 360, 3394–3399; (e) J. W. Gosselinka, A. M. F. Brouwergse, G. van Koten and K. Vrieze, J. Chem. Soc., Chem. Commun., 1979, 1045–1047; (f) M. H. Nguyen and J. H. K. Yip, Organometallics, 2013, 32, 1620–1629; (g) M. H. Nguyen, C. Y. Wong and J. H. K. Yip, Organometallics, 2011, 30, 6383–6392; (h) J. Schneider, P. Du, X. Wang, W. W. Brennessel and R. Eisenberg, Inorg. Chem., 2009, 48, 1498–1506.
21. K. Osakada, T. Hosoda and T. Yamamoto, Bull. Chem. Soc. Jpn., 2000, 73, 923–930.
22. (a) C. R. Patrick and G. S. Prosser, Nature, 1960, 1021; (b) T. Dahl, Acta Chem. Scand., Ser. A, 1975, 29, 699–705; (c) H. Adams, J. L. Jimenez-Blanco, G. Chessari, C. A. Hunter, C. M. R. Low, J. M. Sanderson and J. G. Vinter, Chem. – Eur. J., 2001, 7, 3494–3503; (d) J. R. Lane, G. C. Saunders and S. J. Webb, CrystEngComm, 2013, 15, 1293–1295; (e) A. Hori, H. Takeda, J. R. Premkumar and G. N. Sastry, J. Fluorine Chem., 2014, 168, 193–197; (f) S. M. Hsu, Y. C. Lin, J. W. Chang, Y. H. Liu and H. C. Lin, Angew. Chem., Int. Ed., 2014, 53, 1921–1927.
23. M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham,C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez and J. A. Pople, Gaussian 03W, Gaussian Inc., Wallingford, CT, 2004.
24. L. Rigamonti, A. Forni, M. Manassero, C. Manassero and A. Pasini, Inorg. Chem., 2010, 49, 123–135.
25. J. A. Riddick, W. B. Bunger and T. K. Sakano, Organic Solvents. Physical Properties and Methods of Purifications, Techniques of Chemistry, Wiley-Interscience, New York, 4th edn, 1986, vol. II.
26. M. I. García-Seijo, A. Castiñeiras, B. Mahieu, L. Jánosi, Z. Berente, L. Kollár and M. E. García-Fernández, Polyhedron, 2000, 20, 855–868.
27. (a) G. Annibale, P. Bergamini, V. Bertolasi, M. Cattabriga and V. Ferretti, Inorg. Chem. Commun., 2000, 3, 303–306; (b) G. Annibale, P. Bergamini and M. Cattabriga, Inorg. Chim. Acta, 2001, 316, 25–32.
28. G. M. Sheldrick, SHELXTL 6.14 Program Library, Brüker Analytical Instrument Division, Madison, Wisconsin, USA, 2003.
29. DIAMOND 3.0, Visual Crystal Structure Information System, Crystal Impact, Postfach 1251, D-53002 Bonn, Germany, 2004.

---

Footnotes

† Electronic supplementary information (ESI) available. CCDC 1025112 (1), 1026048 (3) and 1025113 (8). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4nj01686f

‡ Present address: Departamento de Química, Cinvestav, Av. Instituto Politécnico Nacional 2508, San Pedro Zacatenco, 07360, México D.F., Mexico.

---