Reaction mechanisms of metal–metal-bonded carbonyls. Part 15. Reactions of nonacarbonyl(triphenylphosphine)dimanganese and octacarbonylbis( triphenyiphosphine)dimanganese

Abstract

Kinetics of reactions of [{Mn(CO)₄(PPh₃)}₂] with carbon monoxide, oxygen, and triphenylphosphine are reported and the major reaction path in each case is concluded to involve initial reversible homolytic fission. Infrared evidence is adduced for the formation of substantial amounts of [Mn(CO)₃(PPh₃)₂] in cyclohexane after reaction with PPh₃. Reaction with oxygen proceeds by an additional path, not yet fully characterised but of almost equal importance. Data for reaction of [Mn₂(CO)₉(PPh₃)] with CO, PPh₃, and oxygen are also reported. Kinetic, and some thermodynamic, parameters for reactions of the decacarbonyls [M₂(CO)₁₀](M₂= Mn₂, Tc₂, Re₂, or MnRe) and their triphenylphosphine derivatives are compared, and the importance of steric effects in determining the kinetic strengths of the metal–metal bonds is pointed out.