74280-92-5Relevant academic research and scientific papers
Selective cleavage of the Pt-C(alkyl) bond in alkylarylplatinum(II) complexes and mechanism of cis to trans isomerization of the resulting solvento complexes
Alibrandi, Giuseppe,Minniti, Domenico,Scolaro, Luigi Monsù,Romeo, Raffaello
, p. 318 - 324 (2008/10/08)
Protonolysis of the complexes cis-[Pt(PEt3)2(R)(Me)] (R = Me, Ph, mesityl) by H+A- (A- = ClO4-, BF4-, p-toluenesulfonate) in methanol selectively cleaves the alkyl group, yielding cis-[Pt(PEt3)2(R)(MeOH)]+ and methane. The rates show first-order dependence on complex and on proton concentrations, obeying the simple rate law kobsd = kH[H+]. Steric hindrance on the Pt-C bond causes a decrease in rate. A mechanism is proposed that involves rate-determining attack of the proton on the Pt-C bond with release of methane in a three-center transition state. The resulting methanol intermediate spontaneously converts to its trans isomer, and for all systems the isomeric equilibrium lies well to the side of the trans form. At 303.16 K for R = Me, ki = 6.76 × 10-3 s-1, ΔH≠ = 106 ± 4 kJ mol-1, ΔS≠ = +63 ± 12 J K-1 mol-1; for R = Ph, ki = 11.9 × 10-3 s-1, ΔH≠ = 112 ± 3 kJ mol-1, ΔS≠ = +84 ± 8 J K-1 mol-1; for R = mesityl, ki = 28.8 × 10-3 s-1, ΔH≠ = 106 ± 3 kJ mol-1, ΔS≠ = + 75 ± 8 J K-1 mol-1. Isomerization of cis-[Pt(PEt3)2(Me)(MeOH)]+ in diethyl ether-methanol mixtures undergoes mass law retardation by [MeOH]. The rates of isomerization of cis-[Pt(PEt3)2(Me)(S)]+ (S = a series of hydroxylic solvents) are little influenced by the nature of the solvent. As in the case of the related halide species, the isomerization mechanism involves interconversion of two T-shaped 3-coordinate intermediates that show discriminating ability toward scavenging agents.
