Tuning diastereoisomerism in platinum(II) phosphino- and aminothiolato hydrido complexes
Chelate assisted oxidative addition of one equivalent of 2-phosphinothiols (2-(diphenylphosphino)ethanethiol 1, 1-(benzyloxy)-2-(diphenylphosphino)ethanethiol 2 and 2-(diphenylphosphino)-cyclohexanethiol 3) to tetrakis(triphenylphosphine)platinum(0) gives the corresponding hydrido[2-(phosphino-κP)thiolato-κS]triphenylphosphineplatinum(II) complexes 8–10. Temperature variable NMR studies show that these complexes display a chemical equilibrium between the cis-P,P and trans-P,P geometries, strongly displaced toward the trans-P,P configuration (70–90%). XRD studies carried out on crystals of 8 indicate that although the two geometric isomers are present in solution, only the trans-P,P is obtained in the solid state. These results differ from the cis-P,N geometry observed for the related hydrido[2-(amino-κN)thiolato-κS]triphenylphosphineplatinum(II) complexes 5–7 in solution. The crystal structures obtained for these aminothiolate hydrides show that the cis-P,N configuration is the only one observed in the solid state. Chelate assisted oxidative addition of one equivalent of 3-(diphenylphosphino)propanethiol 4 to tetrakis(triphenylphosphine)platinum(0) gives the resultant hydrido[3-(phosphino-κP)thiolato-κS]triphenylphosphineplatinum(II) complex 11. This 3-phosphinothiolate hydride shows in solution only a trans-P,P geometry but presents two chelate ring conformational isomers. Density functional theory calculations have been used to explore the ligand-based stereoelectronic effects that are determinant in the different diastereoisomerism observed in these platinum(II) hydrides (5–11).