Electronic and geometric structure of the 3d-transition metal monocarbonyls MCO, M=Sc, Ti, V, and Cr.
The electronic and geometric structure of the 3d-transition metal monocarbonyls MCO, M=Sc, Ti, V, and Cr was investigated through coupled cluster (CC) and multireference variational methods (MRCI) combined with large basis sets. For the ground and a few low-lying excited states complete potential energy profiles were constructed at the CC-level of theory. The M-CO dissociation energies of the ground states X 4Sigma-,X 5Delta,X 6Sigma+, and X 7A' are calculated to be 36, 27, 18, and 2 kcal/mol for ScCO, TiCO, VCO, and CrCO, with respect to Sc(4F),Ti(5F),V(6D),Cr(7S)+CO(X 1Sigma+). The bonding is rather complicated and could be attributed mainly to pi-conjugation effects between the M and CO pi-electrons, along with weak sigma-charge transfer from CO to M atoms. Almost in all cases the metal atoms appear to be slightly positively charged, at least according to the direction of the dipole moment vectors and the MRCI population densities.
Koukounas
Constantine
C
Laboratory of Physical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, P.O. Box 64 004, 15710 Zografou, Athens, Greece.
Kardahakis
Stavros
S
Mavridis
Aristides
A