Some four- and five-co-ordinate cations of platinum(II) containing alkylphosphine and hydride ligands

Abstract

Hydrogen-1 and ³¹P n.m.r. spectroscopy have been used to study the equilibrium of trans-[PtH(I)(PEt₃)₂] with an additional phosphine L [mol ratio 1 : 1, L = PMe_3-nH_n(n= 0–3) or PEt₃] in CD₂Cl₂ solution. The spectra are temperature dependent and the cation [PtH(PEt₃)₂L]⁺ is observed at –90 °C. These cations (except L = PH₃) have been isolated as [BPh₄]^– salts from reactions in methanol. A mixture of trans-[PtH(I)(PEt₃)₂] and PMeH₂(mol ratio 1 : 2) gives completely reversible temperature-dependent n.m.r. spectra from which the formation of [PtH(PMeH₂)₂(PEt₃)₂]⁺ is inferred. Reaction of [PtH(PEt₃)₃]⁺ with PMeH₂, PMe₂H, or PMe₃ at –90 °C in CD₂Cl₂ gives well resolved spectra of [PtH(PEt₃)L₃]⁺. The spectra show the five-co-ordinate cations to have a trigonal-bipyramidal structure with the PEt₃ groups in equatorial positions.