Photochemistry of μ-hydrido-tetrakis(tertiary phosphine)diplatinum complexes

The present work examines the photochemistry of mu -hydrido-tetrakis(ethylphosphine)diplatinum complexes, trans-trans monohydrido-bridged [(PEt3)(2)HPt(mu -H)PtH(PEt3)(2)][BPh4] (1) and trans-cis dihydrido-bridged [(PEt3)(2)HPt(mu -H-2)Pt(PEt3)(2)][BPh4] (2). The primary photoprocess of these complexes is homolysis of their Pt-Pt bonds. Interesting consequences of Pt-Pt bond dissociation include cleavage of Pt(mu -H)Pt and Pt(mu -H-2)Pt yielding the reactive complexes [(PEt3)(2)PtH2] (3) and [(PEt3)(2)PtH(S)][BPh4] (4) (S: solvent). Depending on experimental conditions, photoproducts 3 and 4 can undergo a multiplicity of reactions. In acetone photoproducts 3 and 4 undergo a thermal coupling reaction forming the trans-cis isomer 2. Selective photolysis of 3 and 4 gives elimination of H-2 and solvent with generation of reactive intermediates [(PEt3)(2)Pt] (5) and [(PEt3)(2)PtH](+) (6). Photogenerated 5 and 6 fragments react cleanly with CO to form 18 electron compounds [(PEt3)(2)Pt(CO)(2)] (7) and [(PEt3)(2)Pt(H)(CO)](+) (8). In CH2Cl2, the photoproducts 5 and 6 could abstract halide from the solvent to form as the only final products [(PEt3)(2)Pt(Cl)CH2Cl] (9) and [(PEt3)(2)Pt(H)Cl] (10). The photoreactions are interpreted in terms of excited state decay channels.