The Photochemistry of the (cycloalkene)(hydro)(trispyrazolylborato)iridium complexes [Ir(eta4-cod)(TpMe2)] and [Ir(eta2-coe)H2(TpMe2)]: the Formation of [IrH4(TpMe2)] and [Ir(CO)H2(TpMe2)]

Photolysis of [Ir(eta(2)-coe)H-2(Tp(Me2))] (1; Tp(Me2)=hydrotris(3,5-dimethylpyrazolyl)borato, coe = (Z)-cyclooctene) in CH3OH gives a mixture of [IrH4(Tp(Me2))] (4) and [Ir(CO)H-2(Tp(Me2))] (5) in a ca. 1 : 1 ratio. Mass-spectral analysis of the distillate of the reaction mixture at the end of the photolysis shows the presence of coe. When pure CD3OD is used as solvent, the deuteride complexes [IrD4(Tp(Me2))] ((D-4)-4) and [Ir(CO)D-2(Tp(Me2))] ((D-2)-5) are obtained. Also the photolysis of [Ir(eta(4)-cod)(Tp(Me2))] (3) (cod = cycloocta-1,5-diene) gives 4 and 5. A key feature of this photoreaction is the intramolecular dehydrogenation of cod with formation of cycloocta-1,3,5-triene, detected by mass spectroscopy at the end of the photolysis. Labeling experiments using CD3OD show that the hydrides in 4 originate from MeOH. When (CH3OH)-C-13 is used as solvent, [Ir((CO)-C-13)H-2(Tp(Me2))] is formed demonstrating that CH3OH is the source of the CO ligand. The observation that the photolysis of both 1 and 3 give the same product mixture is attributed to the formation of a common intermediate, i.e., the coordinatively unsaturated 16e(-) species {IrH2(Tp(Me2))}.