An `ab initio' investigation of the electronic structure of ion-pair enolates NH 2COCH 2CuPH 3, PH 2COCH 2CuPH 3, C 6H 5COCH 2CuPH 3, C 6H 5SOCH 2CuPH 3: the influence of the heteroatom. Part III

Abstract

The electronic structure and the geometry of the phosphinecopperacetamide, the phosphinecopperactylphosphine, the phosphinecopper-acetophenone and the phosphinecoppermethylphenylsulfoxide have been investigated through ab initio calculations. The different coordination modes, ηeta; 1-O, η 3 and η 1-C of the CuPH + 3 cation have been analyzed. The η 1-C coordination of the copper towards the enolate anion is preferred for the acetamide, while the η 3 coordination is the lowest in energy for the methylphenylsulfoxide. For the acetylphosphine and the acetophenone enolate anions the η 1-O and η 1-C coordinations are almost isoenergetic, while the η 3 coordination is higher in energy. A comparison between CuPH + 3 and TiF + 3, interacting with the same enolate anions, shows that a soft metal like copper stabilizes the η 1-C coordination, while a hard metal like titanium prefers the interaction with the other nucleophilic center, i.e. the oxygen.