Synthesis of alkyl- and aryl[hydrotris(pyrazolyl)borato]carbonylruthenium complexes by decarbonylation of alcohols. Synthesis of TpRuH(H-2)(PPh(3)) [Tp equals hydrotris(pyrazolyl)borate], an observable intermediate in the decarbonylation reaction

Treatment of TpRuCl(PPh(3))(CH3CN) (Tp=hydrotris(pyrazolyl)borate) with NaBH4 in ethanol did not yield the expected hydride complex TpRuH(PPh(3))(CH3CN) (2) but rather the methyl carbonyl complex TpRu(CH3)(CO)(PPh(3)) (1b). Formation of 1b was due to decarbonylation of ethanol by 2 generated in situ by NaBH4 reduction of TpRuCl(PPh(3))(CH3CN). Analogous reactions in the presence of other primary alcohols RCH(2)OH (R=H, C2H5, n-C3H7, C6H5, C6H4CH3-4, and C6H4Cl-4) led to the corresponding sigma-organyl complexes TpRuR(CO)(PPh(3)). A common feature of the reactions is that the R groups of alcohols RCH(2)OH become the sigma-organyl groups in the final metal complexes. A mechanism involving metal-eta(2)-aldehyde and -eta(2)-dihydrogen intermediates is proposed for the decarbonylation reaction. This is supported by the observation of the eta(2)-dihydrogen complex TpRuH(H-2)(PPh(3)) (3) during the decarbonylation reaction. 3 was synthesized independently by heating a THF solution of 2 under 40 atm of H-2 at 60 degrees C for 48 h or by heating 2 in CH3OH at 60 degrees C under 6 atm of H-2 for 5-6 h.