Tripodal oxygen and tripodal hydroformylation reactions:: formation of novel rhodium(III) carbonyl bis(acyl) complexes

The rhodium(l) complexes TpmsRh(CO)(2) (1) and TpmsRh(cod) (2) of the tripodal nitrogen ligand tris(pyrazolyl)methanesulfonate, Tpms(-) = [(pz)(3)CSO3](-), catalyze the hydroformylation of 1-hexene. Addition of phosphine has a negative effect on the activity. The hydroformylation activity reaches a maximum at about 60 degreesC. At temperatures above 80 degreesC hydrogenation becomes an important secondary reaction. When the catalysis is performed at 60 degreesC in acetone with 1 or 2 as catalyst precursor all of the rhodium is recovered in the form of the rhodium(III) bis(acyl) complex TpmsRh(CO)(COC6H13)(2) (9). A similar behaviour is observed with rhodium(l) complexes bearing the tripodal oxygen ligand L-OMe(-) = [(cyclopentadienyl)tris(dimethylphosphito-P) cobalt O,O',O''](-). In this case all of the rhodium is transformed into LOMeRh(Co)(COC6H13)(2) (10). These hitherto unknown bis(acyl) rhodium(III) complexes show the same catalytic activity as the rhodium(l) starting compounds. (C) 2003 Elsevier B.V. All rights reserved.