Synthesis and characterisation of boranediyl- and diboranediyl-bridged diplatinum A-frame complexes

Abstract

A series of boranediyl-bridged diplatinum A-frame complexes, [Pt₂X₂(μ-BY)(μ-dmpm)₂] (X = Cl, Br, I; Y = aryl, alkyl, amino, halo; dmpm = bis(dimethylphosphino)methane), were synthesised by the twofold oxidative addition of BX₂Y to [Pt₂(nbe)₂(μ-dmpm)₂] (nbe = norbornene) or to the paddlewheel complex [Pt₂(μ-dmpm)₃]. Similarly, the addition of B₂X₂(NMe₂)₂ (X = Cl, Br) to [Pt₂(nbe)₂(μ-dmpm)₂] provided access to the diborane-1,2-diyl-bridged A-frame complexes [Pt₂X₂(μ-1,2-B₂(NMe₂)₂)(μ-dmpm)₂]. X-ray crystallographic studies of these (BY)_n-bridged complexes show structural trends depending on the steric demands of Y and the nature of X. Analysis of higher-order ³¹P NMR satellites provided information on J_P–Pt and J_Pt–Pt coupling constants, the latter correlating with the Pt⋯Pt distance. All (di)boranediyl complexes also proved unstable towards (successive) loss of the bridging “BY” unit(s), resulting in the formation of [Pt₂X₂(μ-dmpm)₂].