Structural Preferences in Phosphanylthiolato Platinum(II) Complexes

Abstract

The transition‐metal complexes of heterotopic phosphanylthiolato ligands are useful in various reactions which depend on the stereochemistry of the complexes. Bis‐chelate complex [Pt(SCH2CH2PPh2‐κ2 P,S)2] (1) was obtained in good yields by direct base‐free substitution reaction of the corresponding phosphanylthiol (HSCH2CH2PPh2) with K2PtCl4 or by oxidative addition of the same phosphanylthiol to Pt(PPh3)4. In agreement with the antisymbiosis rule, complex 1 shows a cis‐P,P arrangement in solid state crystallizing in the monoclinic system (C2/c). Density functional theory (DFT) calculations on 1 reveal the right characteristics for the preferred cis‐P,P arrangement, rationalizing its formation. Direct base‐free reaction of [PtCl2(1,5‐cyclooctadiene)] with one equivalent of the same phosphanylthiol produce the trinuclear complex [PtCl(μ‐SCH2CH2PPh2‐κ2 P,S)]3 (2) instead of the binuclear structure common in palladium and nickel derivatives. Crystals of 2 are triclinic (P true1‾ ) showing a sulfur‐bridging edge‐sharing cyclic trinuclear complex with square‐planar coordination geometry around the platinum atoms and a Pt3S3 cycle in skew‐boat conformation. This preference for the trinuclear structure was rationalized mechanistically and through conceptual DFT.

Tuning diastereoisomerism in platinum(ii) phosphino- and aminothiolato hydrido complexes

“…Chelate assisted oxidative addition 4,13,22 of one equivalent of 2-(diphenylphosphino)ethanethiol (Hdppet, 1) to tetrakis(triphenylphosphine)platinum (0) gives the corresponding hydrido[2-(diphenylphosphino-kP)ethanethiolato-kS]triphenylphosphineplatinum(II) complex ([Pt(H)(dppet)(PPh 3 )], 8, Scheme 1). Complex 8 is isolated as a white solid in 68% yield and purified by recrystallization in dichloromethane/ether.…”

“…If Hdppet is added to default, a mixture of 8 and the reactant complex is obtained making impossible further separations. On the other hand, if an excess of Hdppet is used, a mixture of 8 and the bischelate [Pt(dppet) 2 ] is obtained, 13,23 which is also difficult to be separated especially if the bischelate complex is present in high quantities. Complex 8 presents a satisfactory EA and has been characterized by IR and NMR spectroscopy, as well as XRD.…”

“…Hydrido[(diphenylphosphino-kP)alkanethiolato-kS]triphenylphosphinoplatinum(II) complexes 9-11 were prepared by chelate assisted oxidative addition 4,13,22 of one equivalent of the corresponding phosphinothiol ligand (2-4) to tetrakis(triphenylphosphine)platinum(0) in moderate yields and were characterized by IR and NMR spectroscopy.…”

“…In this context, the diastereochemistry of these complexes has particular importance, as different diastereomers should present different activity, regioselectivity, and enantioselectivity in a given catalytic process. 7 As part of a project on the synthesis of new amino-and phosphinothiolato complexes of the group 10 metals and on the analysis of the ligand-based stereoelectronic effects that are determinants in the coordination conformations around the metal, 3,[8][9][10][11][12][13] we now report the preparation of new platinum(II) hydride complexes (8)(9)(10)(11) with 2-phosphinoethanethiolate ligands (2-(diphenylphosphino)ethanethiolate dppet 8, 1-(benzyloxy)-2-(diphenylphosphino)ethanethiolate bdppet 9, and 2-(diphenylphosphino)cyclohexanethiolate dppcyt 10) and a 3-phosphinothiolate ligand (3-(diphenylphosphino)propanethiolate dpppt 11). We also present, for the first time to our knowledge, the crystal structure determined by the X-ray analysis of a platinum(II) hydride complex with 2-phosphinoalkylthiolate ligand (8) and with 2-aminothiolate ligands: cysteamine (5) and natural chiral ligands methyl (cysMe) and ethyl (cysEt) ester-protected natural L-cysteine derivatives (6)(7).…”

Platinum phosphinothiolato hydride complexes: synthesis, structure and evaluation as tin-free hydroformylation catalysts

“…Furthermore, in a similar addition involving HSCH 2 CH 2 PPh 2 (dppet), this has been found to be the rate-determining step, according to conceptual DFT calculations. 14 The bischelate obtained in this way may contain small amounts of trans-[Pt(sarp) 2 ] which can be converted to cis-[Pt(sarp) 2 ] by further heating at 110 °C in toluene. The greater thermodynamic stability of the cis isomer is predicted by the greater trans influence of phosphorous over sulfur (or by the so called antisymbiosis rule) 15 while steric hindrance would favour the trans isomer.…”