CARBON-MONOXIDE ACTIVATION BY POLY(1-PYRAZOLYL)BORATOIRIDIUM COMPLEXES

The syntheses Of [IrH(HBPz3)(COOH)(CO)] (2), [IrH(HBPz3)(COOMe)(CO)] (5) and [IrH(HBPz3)-(COOEt)(CO)] (6) are described. They are prepared by the direct reaction of [Ir(HBPZ3)(CO)2] (1) with H2O, MeOH, or EtOH, respectively. Compound (2) is stable in the solid state and in solution at room temperature, but decomposes in refluxing acetonitrile to give the dihydride [IrH2(HBPZ3)(CO)] (3). The protonations of 1, 2 and 5 with HBF4.H2O lead to the cationic complex [IrH(HBPZ3)(CO)2]BF4 (4). Complex 5 is also obtained by reaction of 2 with methanol or by treatment of 4 with KOH/MeOH. The complex [Ir(BPz4)(CO)2] (7) also reacts with H2O and MeOH at room temperature, in the presence of CO; these reactions do not go to completion. The products of these reactions are most probably [IrH(BPZ4)(COOH)(CO)] and [IrH(BPz4)(COOMe)(CO)]. Treatment of 7 with H2O in refluxing acetonitrile leads to [IrH2(BPz4)(CO)] (8).