AB INITIO STUDY OF CHEMICAL ACTIVATION AND HYDROGENATION OF WHITE PHOSPHORUS IN REACTION WITH RHODIUM TRIHYDRIDE COMPLEX

The four-stage mechanism of reaction of the rhodium trihydride complex [(triphos)RhH3] (triphos=1,1,1tris(diphenylphosphanylmethyl) ethane) with the white phosphorus molecule resulting in the phosphane and the cyclo-P-3 complex [(triphos) M(eta(3)-P-3] is analyzed on the basis of ab initio calculations of reactants, products, and intermediate complexes of reaction. It is shown that generation of the transient complex [(triphos) RhH(eta(1):eta(1)-P-4)] followed by intramolecular hydrogen atom migration from the metal to one of the phosphorus atoms is the energetically favourable process. Calculations also show that P-4 molecule is activated by coordination to the above complex: the metal-bonded P-P edge is broken, and the tetrahedron P-4 is opened to form the butterfly geometry. This activation is realized mainly due to the one-orbital back donation of 4d-electron density from the atom of Rh to the unoccupied antibonding triple degenerate t(1)*-MO of P-4.