| Abstract
| - A series of new bis(amidate)-bis(amido) Ti and Zr complexes were synthesized and characterized. The solid-state structures indicate exclusively bidentate metal binding. Geometric isomerism is dependent upon the steric properties of the amidate ligand. By NMR spectroscopy, it was determined that one geometric isomer is predominant. DFT calculations on the geometrical isomers agreed with experimental observations, and bonding analysis indicated a reactive M−N amido π bond as the HOMO and a vacant d orbital as the LUMO.
- Easily prepared and highly modular organic amide proligands have been used to synthesize a series of newbis(amidate)-bis(amido) Ti and Zr complexes via protonolysis. These complexes have been structurally characterizedby NMR spectroscopy and X-ray crystallography. The solid-state molecular structures of these complexes indicatethat the amidate ligands bind to the metal centers in an exclusively bidentate fashion, resulting in discrete monomericspecies. Geometric isomerism in these species is highly dependent upon the steric characteristics of the proligandsutilized in the synthesis. In solution, these complexes are observed to isomerize on the NMR time scale, with oneisomer being predominant. Bonding in the bis(amidate)-bis(amido) complexes was investigated by DFT calculations.The geometric isomers predicted by theory matched the experimentally observed results, within experimental error.The orbitals associated with amidate−metal bonding are energetically well below the frontier orbitals. The HOMOin these complexes is a π orbital associated with amido ligand-to-metal bonding character, while the LUMO in allcases is a vacant d orbital on the metal center.
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