PRESSURE EFFECTS ON BIMOLECULAR REDUCTIVE QUENCHING OF THE PLATINUM(II) DIMER PT2(MU-ETA-2-H2P2O5)4(4-) BY ORGANIC SUBSTRATES

Pressure effects are reported for the quenching dynamics of the lowest energy excited state of the d8-d8 dimer Pt2(μ-η2-H2P2O5)44- (3Pt2⋆). Volumes of activation (ΔV⋆) are reported for the H atom abstraction by 3Pt2⋆ from various organic substrates and for O2 quenching of 3Pt2⋆ in methanol solution. The H atom donors studied include a series of benzyl alcohols, allyl alcohol, tributyltin hydride, and benzyl methyl ether. Volumes of activation of-5.4 ± 0.6 cm3 mol-1 and-4.1 ± 0.7 cm3 mol-1 have been measured for quenching by benzyl alcohol and benzyl methyl ether, respectively. These negative ΔV⋆ values suggest an associative interaction between the excited state dimer and the H atom donor. The mechanistic implications of the pressure effects on the rates for other quenchers are discussed. © 1990, American Chemical Society. All rights reserved.