DENSITY-FUNCTIONAL STUDY ON THE ELECTRONIC-STRUCTURE OF TRIOXORHENIUMORGANYLS

A linear combination of Gaussian-type orbital density functional (LCGT O-DF) investigation of three rhenium-oxo complexes, RReO(3) (R = CH3, eta(1)-C6H5, eta(5)-C5H5 is presented, showing the influence of the th ree different types of ligand-to-metal bonding sigma-alkyl, sigma-aryl , and pi-aryl, respectively. The calculated ionization potentials of t hese compounds are compared to their He I photoelectron spectra and fo und to be in excellent agreement. In particular, the present results f or H3C-ReO3 are much improved over various other theoretical approache s. Special attention is drawn to the -ReO3 fragment energy levels and to the nonbonding 2p lone pairs on the oxygen atoms; their relative en ergetic positioning allows conclusions on the charge distribution and thus on the Lewis acidity of the rhenium atom in the active site -ReO3 . To assist this interpretation, Mulliken fragment charges and calcula ted dipole moments are discussed. A recently proposed relationship bet ween the oxygen charge within the -ReO3 fragment and O-17 NMR shifts i s supported.