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Issue 9, 2011
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Stereochemistry of post-transition metal oxides: revision of the classical lone pair model

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Abstract

The chemistry of post transition metals is dominated by the group oxidation state N and a lower N-2 oxidation state, which is associated with occupation of a metal s2 lone pair, as found in compounds of Tl(I), Pb(II) and Bi(III). The preference of these cations for non-centrosymmetric coordination environments has previously been rationalised in terms of direct hybridisation of metal s and p valence orbitals, thus lowering the internal electronic energy of the N-2 ion. This explanation in terms of an on-site second-order Jahn–Teller effect remains the contemporary textbook explanation. In this tutorial review, we review recent progress in this area, based on quantum chemical calculations and X-ray spectroscopic measurements. This recent work has led to a revised model, which highlights the important role of covalent interaction with oxygen in mediating lone pair formation for metal oxides. The role of the anion p atomic orbital in chemical bonding is key to explaining why chalcogenides display a weaker preference for structural distortions in comparison to oxides and halides. The underlying chemical interactions are responsible for the unique physicochemical properties of oxides containing lone pairs and, in particular, to their application as photocatalysts (BiVO4), ferroelectrics (PbTiO3), multi-ferroics (BiFeO3) and p-type semiconductors (SnO). The exploration of lone pair systems remains a viable a venue for the design of functional multi-component oxide compounds.

Graphical abstract: Stereochemistry of post-transition metal oxides: revision of the classical lone pair model

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Publication details

The article was received on 13 Apr 2011 and first published on 13 Jun 2011


Article type: Tutorial Review
DOI: 10.1039/C1CS15098G
Citation: Chem. Soc. Rev., 2011,40, 4455-4463
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    Stereochemistry of post-transition metal oxides: revision of the classical lone pair model

    A. Walsh, D. J. Payne, R. G. Egdell and G. W. Watson, Chem. Soc. Rev., 2011, 40, 4455
    DOI: 10.1039/C1CS15098G

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