A simple route to highly active ruthenium catalysts for formylation reactions with hydrogen and carbon dioxide

A simple route to ruthenium catalysts suitable for formamide production from amines, hydrogen and carbon dioxide is reported. The formylation of 3-methoxypropylamine has been employed as a test reaction. Highly active and selective ruthenium based catalysts were formed in situ under reaction conditions from solid RuCl3 in the presence of triphenylphosphine (PPh3) and 1,2-bis(diphenylphosphino)ethane. While RuCl3 does not catalyze the reaction effectively, the addition of phosphines led to nearly five-fold increase in rate. The achieved turnover frequencies are comparable to those of synthesized reference Ru-phosphine complexes. As a consequence of the high activity only very small amounts (similar to 300 ppm) of both RuCl3 and the phosphine are necessary to catalyze effectively the formylation reaction. Despite the very low concentration of the Ru complex, the structure of the in situ formed active complex was elucidated by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy. Both indicated similar local structure for the in situ formed complex and a Ru-reference complex after reaction. (C) 2004 Elsevier B.V. All rights reserved.