title: Electronic and geometric structure of the 3d-transition metal monocarbonyls MCO, M=Sc, Ti, V, and Cr.
abstract: 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.
authors.affiliation: Laboratory of Physical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, P.O. Box 64 004, 15710 Zografou, Athens, Greece.
authors.forename: Constantine
authors.initials: C
authors.lastname: Koukounas
authors.forename: Stavros
authors.initials: S
authors.lastname: Kardahakis
authors.forename: Aristides
authors.initials: A
authors.lastname: Mavridis