Nature and cooperativity of metal−ligand bonds in groups ۵, ۷, ۹ and ۱۱half-sandwich cyclopentadienyl complexes

Half-sandwich complexes that have an metal center attached to a cyclopentadienyl ligand haveattracted much attention due to their unique electronic and chemical properties. The term sandwichcompound was introduced in organometallic nomenclature in ۱۹۵۶ in a report by Dunitz and coworkerswho confirmed the structure of ferrocene by X-ray crystallography [۱]. In this work, weinvestigate the electronic structure and bonding interactions in a set of half-sandwich complexesusing advanced computational methods and recently developed methodolgies [۲, ۳]. The aim ofthis project is to provide a detailed theoretical investigation of the nature of bond, and cooperativityof bonds for half-sandwich complexes containing cyclopentadienyl and carbonyl ligands with thegeneral formula [M(η۵–Cp)(CO)n] (M=Cu+, Au+, Ag+, n=۱, M= Co+, Ir+, Ru+, n=۲, Mn+, Re+, Tc+,n=۳, V+, Nb+, Ta+, n=۴). The geometries of all complexes were fully optimized at the B۳LYP,B۹۷۱, M۰۶-D۳, M۰۶L and MP۲ levels with the def۲-TZVP basis set using the GAUSSIAN-۰۹program without any symmetry restrictions. Vibrational frequency analysis, calculated at all levelsof theory, indicates that the optimized structures are at the stationary points corresponding to localminima without any imaginary frequency.The results indicate that the type and degree ofcooperativity of bonds in the series of these complexes depend highly on the type and nature ofcentral metal ion.

Keywords:

Theoretical study , Half-sandwich compounds , Cooperativity of bonds , Nature of bonds