PROTONATION OF THE CO-RH BOND IN CORH(MU-CO)(CO)(2)(MU-DPPM)(2)

The electronic structure of CoRh(mu-CO)(CO)(2)(mu-H2PCH2PH2)(2) and Co Rh(mu-H)(mu-CO)(CO)(2)(mu-H2PCH2PH2)(2) has been investigated by means of density functional calculations (DFT). The tetrahedral environment around the cobalt atom is the origin of the lack of direct metal-meta l interaction in the former complex. In the protonated form a three-ce nter, two-electron interaction emerges, inducing a slight lessening of the Co-Rh separation. The fluxionality process has also been investig ated. The energy barrier for the exchange of the semibridging carbonyl with the terminal CoCO carbonyl has been computed to be 19 kcal mol(- 1). A second pathway involving the terminal RhCO group appears 18 kcal mol(-1) above.