Amine, amido, and imido complexes of tantalum supported by a pyridine-linked bis(phenolate) pincer ligand: Ta - N π-bonding influences pincer ligand geometry

Ian A. Tonks, Larry M. Henling, Michael W. Day, John E. Bercaw

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29 Scopus citations

Abstract

A series of tantalum imido and amido complexes supported by a pyridine-linked bis(phenolate) ligand has been synthesized. Characterization of these complexes via X-ray crystallography reveals both C s and C 2 binding modes of the bis(phenolate) pyridine ligand, with complexes containing two or fewer strong jr-donor interactions from ancillary ligands giving C s symmetry, whereas three strong jr-donor interactions (e.g., three amido ligands or one amido ligand and one imido ligand) give C 2-symmetric binding of the bis(phenolate)pyridine ligand. DFT calculations and molecular orbital analyses of the complexes have revealed that the preference for C s-symmetric ligand binding is a result of tantalum - phenolate π-bonding, whereas in cases where tantalum - phenolate π-bonding is overridden by stronger Ta - N π-bonding, C 2-symmetric ligand binding is preferred, likely because conformationally this is the lowest-energy arrangement. This electronically driven change in geometry indicates that, unlike analogous metallocene systems, the bis(phenolate)pyridine pincer ligand is not a strong enough π-donor to exert dominant control over the electronic and geometric properties of the complex.

Original languageEnglish (US)
Pages (from-to)5096-5105
Number of pages10
JournalInorganic chemistry
Volume48
Issue number12
DOIs
StatePublished - Jun 15 2009

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