C-H activation by [bis(dialkoxyphosphino)ethane]platinum(0) and [bis(diaminophosphino)ethane]platinum(0) complexes: Platinum-platinum dimer formation limits yields

Article abstract of DOI:10.1021/om00020a012

Syntheses of new bidentate phosphorus-containing ligands and platinacycles that insert into C-H bonds of unactivated hydrocarbons under mild conditions are reported. The reactivities of the platinum neopentyl hydride species can be substantially increased by introducing oxygen- or nitrogen-containing substituents onto the phosphorus atoms. Dimeric species that are formed from the Pt(0) species are identified by comparing their ³¹P NMR spectra with simulated spectra. Further evidence for these dimers was obtained by cleaving them to mononuclear derivatives with alkyne and phosphine ligands. Formation of these dimers limits the efficiency of hydrocarbon activation. The extent of dimerization that occurs during alkane activation depends upon the steric crowdedness about the Pt(0) center. The X-ray structure of [-(CH₂)₄-C(CH₂O)₂]PCH ₂CH₂P[(OCH₂)₂C-(CH₂) ₄-]Pt(neo-Pe)Cl (9) has been determined: C₂₁H₃₉O₄PtCl₂·CH ₂Cl₂, M_r = 732.96, monoclinic, space group P2₁/n (No. 14), a = 14.667(3) A? b = 11.384(6) A?, c = 17.110(4) A?, β = 100.62(2)°, V = 2808(3) A?³, Z = 4, D_calc = 1.734 g cm^-3, μ(MO Kα) = 54.74 cm^-1, R = 0.048, R_w = 0.055.