Kinetic studies of CO substitution of metal carbonyls in the presence of O-atom transfer reagents

Abstract

Kinetic studies of CO substitution of metal carbonyls in the presence of O-atom transfer reagents show the reaction rates are first-order in metal carbonyl and in O-atom transfer reagent concentrations, but zero-order in entering-ligand concentration. This suggests an associative mechanism where a carbonyl C-atom is attacked by the O-atom of the reagent, affording the good leaving group CO 2 and generating an active intermediate which readily reacts with the entering ligand to produce the monosubstituted product. Metal carbonyls that have been investigated include the mononuclear compounds M(CO) 6 (M = Cr, Mo, W), M(CO) 5L, and M(CO) 5 (M = Fe, Ru, Os) as well as the cluster compounds (M 3(CO) 12 (M = Fe, Ru, Os), M 2(CO) 10 (M = Mn, Re), M 3(CO) 11 L (M = Fe, Ru, Os), and M 4(CO) 12 (M = Co, Ir). Most of the studies involve reactions with (CH 3) 3 NO, but other O-atom transfer reagents studied include C 6H 5IO, other amine oxides, pyridine oxides, ( p-CH 3OC 6H 4) 2EO (E = Se, Te), (C 6H 5) 3EO (E = P, As, Sb), and (C 6H 5)SO. Various factors relating to the metal carbonyls and to the O-atom transfer reagents that effect the rates of CO substitution are discussed.