Are Metallocene-Acetylene (M = Ti, Zr, Hf) Complexes Aromatic Metallacyclopropenes?

作者：Jemmis Eluvathingal D^*; Roy Subhendu; Burlakov V V; Jiao H; Klahn M; Hansen S; Rosenthal U

来源：Organometallics, 2010, 29(1): 76-81.

DOI：10.1021/om900743g

The bonding nature of metallocene acetylene complexes Cp(2)M(eta(2)-H(3)SiC(2)SiH(3)) 1M and CP(2)M (eta(2)- HC(2)H) 1M' (M = Ti, Zr, Hf) wits studied by density functional theory method. It is found that this acetylene complex has indeed it metallacyclopropene moiety with two in-plane M-C sigma-bonds and one out-of-plane pi-bond interacting with the metal center, resulting in the formation of it delocalized three-center and two-electron (3c-2e) system. Along with its delocalized out-of-plane bonding, this complex has been characterized its aromatic on the basis of the computed stabilizing energy and negative nucleus-independent chemical shifts (NICS). The aromatic stabilization increases from Ti to Zr and Hf, and this is because of the increased charge separation between the CP2M fragment and the H(3)SiC(2)SiH(3) (also HC(2)H) unit. The decrease of the M-C bond length from Zr to Hf is attributed to the increased s character of both M and C hybridization of the M-C a-bonds.

• 出版日期2010-1-11