Selective hydrogenation of polyene to monoene by cobalt carbonyl complex catalysts bearing tert-phosphine

Abstract

The selective hydrogenation of 1,5,9-cyclododecatriene to cyclododecene by use of a series of complex catalysts of the type [Co(CO)₃PR₃]₂(R = alkyl, aryl) in homogeneous phase has been studied with special interest in the relations between the σ-donor strength of used tert-phosphine and catalyst activity. The complex containing trialkylphosphines are stable enough to be recovered after the reaction and exerted almost complete selectivity. The mechanism of the selective hydrogenation is postulated in view of the effect of σ-donor ligand which modifies the equilibrium condition between σ- and π-allyl type reaction-intermediates produced by the addition of metal hydride to diene and also from in view of the configurational factors which may influence the stability of these intermediates.