THE PHOTOCHEMISTRY OF THE (CYCLOALKENE)(HYDRO)(TRISPYRAZOLYLBORATO)IRIDIUM COMPLEXES [IR(ETA(4)-COD)(TP(ME2))] AND [IR(ETA(2)-COE)H-2(TP(ME2))] - THE FORMATION OF [IRH4(TP(ME2))] AND [IR(CO)H-2(TP(ME2))]

Photolysis of [Ir(eta(2)-coe)H-2(Tp(Me2))] (1; Tp(Me2)=hydrotris(3,5-d imethylpyrazolyl)borato, coe = (Z)-cyclooctene) in CH,OH gives a mixtu re 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 mixtur e at the end of the photolysis shows the presence of coe. When pure CD 3OD 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 photolys is 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 deh ydrogenation of cod with formation of cycloocta-1,3,5-triene, detected by mass spectroscopy at the end of the photolysis. Labeling experimen ts 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 CH,OH is the source of the CO ligand. The observati on that the photolysis of both 1 and 3 give the same product mixture i s attributed to the formation of a common intermediate, i.e., the coor dinatively unsaturated 16e(-) species {IrH2(Tp(Me2))}.