Platinum(II) complexes with ligands (RO)2PCH2P(OR)2(R = Me, Et, Ph, or C6H4Me-4); crystal structure of cis,cis-[Pt2Me4{µ-(EtO)2PCH2P(OEt)2}2]

Abstract

Reaction of the ligands (RO)₂PCH₂P(OR)₂(R = Me, Et, Ph, or C₆H₄Me-4) with the compounds [Pt₂Me₄(µ-SMe₂)₂] or [PtX₂(SMe₂)₂](X = Cl, Br, or I) gives the corresponding complexes cis,cis-[Pt₂Me₄{µ-(RO)₂PCH₂P(OR)₂}₂](1) and cis,cis-[Pt₂X₄{µ-(RO)₂PCH₂P(OR)₂}₂](2). Complexes (2) with R = Me or Et were also prepared by treating [PtX₂(SMe₂)₂] with Cl₂PCH₂PCl₂, followed by reaction with methanol or ethanol respectively. The crystal structure of the complex cis,cis-[Pt₂Me₄{µ-(EtO)₂PCH₂P(OEt)₂}₂] has been determined by X-ray diffraction methods [space group P2₁/a, a= 28.792(8), b= 10.560(2), c= 11.660(5)Å, β= 99.63(3)°, and Z= 4; R= 0.051 for 3 525 independent reflections with I 2.5σ(I)]. In the molecular structure, two cis-PtMe₂ fragments are bridged by two (EtO)₂PCH₂P(OEt)₂ ligands to form an eight-membered Pt₂P₄C₂ ring with C_s boat–chair conformation and a Pt ⋯ Pt separation of 3.459(1)Å. Studies by ¹H and ³¹P n.m.r. spectroscopy indicate that all complexes (1) have this conformation but that complexes (2) adopt a chair conformation. The factors affecting both the formation of mononuclear or binuclear complexes with diphosphinomethane ligands and the conformations adopted by binuclear complexes are interpreted in terms of steric effects of the ligands.