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

• Published in: Journal of photochemistry and photobiology. A, Chemistry Chemistry, 2001-11, Vol.144 (2-3), p.101-106
• Main Authors: Boaretto, Rita, Sostero, Silvana, Traverso, Orazio
• Format: Article
• Language: English
• Subjects: Absorption spectra; Chemistry; Exact sciences and technology; General and physical chemistry; Hydridodiplatinum complexes; Photochemistry; Photolysis; Physical chemistry of induced reactions (with radiations, particles and ultrasonics)
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/S1010-6030(01)00545-7

The present work examines the photochemistry of μ-hydrido-tetrakis(ethylphosphine)diplatinum complexes, trans–trans monohydrido-bridged [(PEt3)2HPt(μ-H)PtH(PEt3)2][BPh4] (1) and trans–cis dihydrido-bridged [(PEt3)2HPt(μ-H2)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(μ-H)Pt and Pt(μ-H2)Pt yielding the reactive complexes [(PEt3)2PtH2] (3) and [(PEt3)2PtH(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 H2 and solvent with generation of reactive intermediates [(PEt3)2Pt] (5) and [(PEt3)2PtH]+ (6). Photogenerated 5 and 6 fragments react cleanly with CO to form 18 electron compounds [(PEt3)2Pt(CO)2] (7) and [(PEt3)2Pt(H)(CO)]+ (8). In CH2Cl2, the photoproducts 5 and 6 could abstract halide from the solvent to form as the only final products [(PEt3)2Pt(Cl)CH2Cl] (9) and [(PEt3)2Pt(H)Cl] (10). The photoreactions are interpreted in terms of excited state decay channels.