84624-72-6Relevant academic research and scientific papers
Reversible formation of Pt2(μ-H)2H(PEt3)4+ and Pt2(μ-H)H2(PEt3)4+ from the cis and trans isomers of dihydrobis(triethylphosphine)platinum(II)
Paonessa, Ralph S.,Trogler, William C.
, p. 1038 - 1048 (2008/10/08)
Irradiation of Pt(C2O4)L2, where L = P(C2H5)3, in CH3CN solvent under a hydrogen atmosphere produces [Pt2(μ-H)2HL4][O2CH], 1[O2CH], and CO2. Dimer 1 can also be prepared by the condensation reaction between PtH2L2 (a 90:10 trans:cis equilibrium mixture) and PtH(S)L2+, where S = a solvent such as acetone. When PtD2L2 is used in the reaction, deuterium is only incorporated into the bridging positions. Analyses of the spin and isotopic distribution patterns in the 31P, 1H, and 195Pt NMR spectra establish a solution geometry for 1 based on a cis-PtH2L2 molecule bound to the PtHL2+ fragment. The solution chemistry of 1 depends dramatically on the counterion. Basic anions X = I-, OCH3-, and O2CH- generate small equilibrium concentrations of PtH2L2, PtHXL2, and [PtH(S)L2]X. For example, 1[O2CH] reacts completely in the presence of C2H4 to yield Pt(C2H4)L2 whereas 1[B(C6H5)4] exhibits no such reactivity. Complex 1 efficiently catalyzes the decomposition of formic acid at 25°C; however, formate ion must be added in excess to promote the reaction. Monomers appear to be the active catalysts. The species 1[OH] formed by the addition of H2O to PtH2L2 also catalyzes the hydration of acetonitrile to acetamide. A symmetrical isomer, Pt2(μ-H)H2L4+ (2), of dimer 1 can be generated by the UV photolysis of Pt(C2O4)L2 in methanol. It appears that the initially formed trans-PtH(OCH3)L2 complex undergoes β-hydride abstraction to stereoselectively yield trans-PtH2L2. This species is trapped by trans-PtH(OCH3)L2 or [trans-PtH(S)L2][CH3O] to form 2 before isomerization to cis-PtH2L2 (and thereby 1) takes place. Dimer 2 is thermodynamically unstable with respect to 1, and bases such as pyridine or I- catalyze the isomerization. The relationship between the structures, fluxionality, and reactivity properties of 1, 2, and related dinuclear hydrido complexes is discussed. Lack of facile exchange between bridging and terminal hydrides in 1 and 2 is attributed to the trans disposition of terminal hydrogen to the bridging hydrogens.
