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Issue 2, 2005
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Neutral carbene analogues of the heaviest Group 13 elements: Consideration of electronic and steric effects on structure and stability

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Abstract

The neutral monovalent Group 13 β-diketiminato complexes [CH{(CF3)2CN-2,6-iPr2C6H3}2In] and [CH{(Me)2CN-2,6-iPr2C6H3}2Tl] have been synthesised by analogous ‘one-pot’ procedures involving reaction of [KN(SiMe3)2] with the appropriate β-imino-enamine and Group 13 iodide. The structure of the indium complex reveals that replacement of the ligand backbone methyl groups of the previously reported complex [CH{(Me)2CN-2,6-iPr2C6H3}2In] with trifluoromethyl substituents results in only minor modifications to the dimensions of the NCCCNIn metallacycle. The electronic structures of both indium species were interrogated by DFT calculations to reveal similar frontier molecular orbital schemes. In agreement with calculations performed previously on the aluminium and gallium complexes, [CH{(Me)2CN-2,6-iPr2C6H3}2Al] and [CH{(Me)2CN-2,6-iPr2C6H3}2Ga], the HOMO in both indium species comprises a metal-based sp-hybrid while the LUMO is a ligand-based orbital of π symmetry. The vacant indium p-orbital is represented by the LUMO + 1. Although incorporation of the fluorinated substituents results in a stabilisation of the system overall, the stabilities and observed structural features of the complexes are reasoned to be primarily a result of the steric profile of the very bulky ligands and not through any redistribution of the electron density within the cyclic species. The thallium complex is isostructural to the analogous and previously reported aluminium, gallium and indium species. The greater stability of the monovalent state however is reflected in a reordering of the orbital energies and a stabilisation of the metal-based orbitals in the frontier region of the MO scheme.

Graphical abstract: Neutral carbene analogues of the heaviest Group 13 elements: Consideration of electronic and steric effects on structure and stability

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Publication details

The article was received on 20 Sep 2004, accepted on 19 Nov 2004 and first published on 07 Dec 2004


Article type: Paper
DOI: 10.1039/B414462G
Citation: Dalton Trans., 2005,0, 273-277

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    Neutral carbene analogues of the heaviest Group 13 elements: Consideration of electronic and steric effects on structure and stability

    M. S. Hill, P. B. Hitchcock and R. Pongtavornpinyo, Dalton Trans., 2005, 0, 273
    DOI: 10.1039/B414462G

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