Syntheses of mono- and dinuclear silylplatinum complexes bearing a diphosphino ligand via stepwise bond activation of unsymmetric disilanes

Abstract

Zero-valence platinum complex [Pt(dppe)(η²-C₂H₄)] (1, dppe = 1,2-bis(diphenylphosphino)ethane) treated with disilanes HR¹R²SiSiMe₃ (a, R¹ = R² = Me; b, R¹ = R² = Ph; c, R¹ = H, R² = Ph) afforded the corresponding disilanylplatinum hydrides [Pt(dppe)(H)(SiR¹R²SiMe₃)] (2a–c) by oxidative addition of the Si–H bond to the platinum center. The 1,2-silyl migration in 2a,b led to the formation of bis(silyl)platinum complexes [Pt(dppe)(SiHR¹R²)(SiMe₃)] (3a,b) with a first-order rate constant of 7.2(2) × 10⁻⁴ s⁻¹ at 25 °C for 2a and 3.86(4) × 10⁻⁴ s⁻¹ at 40 °C for 2b, whereas 2c with R¹ = H followed by the transient generation of 3c dimerized rapidly to give the bis(μ-silylene)diplatinum complex [Pt(dppe)(μ-SiHPh)]₂ (4c) in a mixture of cis/trans isomers. Heating of the toluene solution of 3b at 100 °C resulted in a similar dimerization to 4b. In addition, a trinuclear platinum complex [Pt₃(dppe)₃(μ₃-SiPh)₂] (5) with a trigonal bipyramidal Pt₃Si₂ core arose from the reaction of 4c with 1 at 60 °C in toluene. Unsymmetric disilanes therefore accomplished the syntheses of various monomeric and dimeric platinum complexes via 1,2-hydrogen and silyl migration to the platinum center.