Studies of the oxidative addition of some substrates containing carbon–heteroatom bonds to some tungsten and platinum complexes

Abstract

The oxidative addition of some substrates containing carbon–heteroatom bonds to some tungsten and platinum complexes is analysed from a frontier orbital point of view. For the tungsten complexes the main attention is focused on [WCl₂(PR₃)₄] and for the platinum complexes on [Pt(PR₃)₄]. The tungsten complex is able to cleave carbon–heteroatom bonds giving two fragments of the substrate which add to the tungsten complex, whereas with the platinum complex the carbon–heteroatom bond adds to the metal. It is suggested that the first step in the reaction of the d⁴ tungsten complex with the substrates is a nucleophilic attack of the heteroatom in the substrate at the tungsten atom, an end-on interaction, followed by a side-on co-ordination. The oxidative addition is proposed to take place by electron transfer from a tungsten d orbital to the antibonding carbon–heteroatom orbital leading to cleavage of this bond. In the case of the platinum complex the first part of the reaction is also suggested to be an end-on interaction of the heteroatom in the substrate at the platinum atom followed by side-on co-ordination leading to the product.