Stereoselective Decarbonylation of Methanol to Form a Stable Iridium(III) <i>trans</i>-Dihydride Complex

Thermolysis of the known cationic iridium complex [(PNP)Ir(C6H5)H]PF6 (PNP = 2,6-bis-(di-tert-butylphosphinomethyl)pyridine) in methanol results in reductive elimination of benzene and stereoselective methanol decarbonylation to form the new iridium(III) trans-dihydride carbonyl complex [(PNP)Ir(CO)H2]PF6 (trans-2). The iridium(III) dihydride complex [(PNP)Ir(H)2]PF6 (3) is formed as a minor product. cis-[(PNP)Ir(CO)H2]PF6 (cis-2) has been independently prepared by the reaction of dihydride 3 with CO and undergoes reductive elimination of hydrogen at room temperature to form the iridium(I) carbonyl [(PNP)Ir(CO)]PF6 (4), demonstrating that cis-2 is not an intermediate in the decarbonylation reaction.