Oxidative addition of water by an iridium PCP pincer complex: Catalytic dehydrogenation of alkanes by IrH(OH){C6H3-2,6-(CH2PBu2t)(2)}

The dehydrogenation of IrH2{C6H3-2,6-(CH2PBu2t)(2)} (1) by tert-butylethyle ne followed by reaction with an excess of water leads to the isolation of I rH(OH){C6H3-2,6-(CH2PBu2t)(2)} (2) in nearly quantitative yield. The hydrid e hydroxo complex has been characterized by multinuclear NMR spectroscopy a s well as a single-crystal X-ray structure determination. An isotopic label ing study with D2O indicates that 2 arises from the oxidative addition of w ater to the intermediate 14-electron complex Ir{C6H3-2,6-(CH2PBu2t)(2)}. Th e title complex is an efficient catalyst for the transfer dehydrogenation o f cyclooctane to cyclooctene but shows no catalytic activity for the hydrox ylation of the alkane by water. The conversion of 1 to 2 can be reversed by placing a solution of 2 under 1 atm of H-2 at 25 degreesC.