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Alkoxo (OR) and aryloxo (OAr) groups are versatile ancillary ligands in metalorganic chemistry and can be used to tune steric and electronic properties, particularly of mid- to high oxidation state metal centres.
In addition, the hydrolytic sensitivity of transition and main group metal alkoxides makes them useful precursors to oxide materials.

The examples given below illustrate our interests in the synthesis, structure, dynamic behaviour and reactivity of metal alkoxides and their derivatives.

Group 4

The Lewis acidic nature of M(IV) complexes in this group provide opportunities for a range of catalytic applications. In collaboration with ICI, we have studied role of Group 4 metal alkoxides in polyethyleneterephthalate (PET) polymerisation and in the catalysis of isocyanate reactions.

In a collaboration with Dr Simon Doherty we are currently developing ligand systems for better control of Group 4 catalysed reactions.

Group 4 elements are important components of electroceramics such as lead zirconium titanate (PZT) and barium titanate. Sol-gel processing of these and related materials is based upon hydrolysis of alkoxide solutions to which have been added various "modifiers" which are usually the source of multidentate ligands. We have studied the species produced when acetylacetone (acacH) is added to Ti(OR)₄ and have shown that the 1:1 reaction products [Ti(OR)₃(acac)] are dimeric and readily undergo ligand redistribution in solution to give Ti(OR)₄ and [Ti(OR)₂(acac)₂]. The hydrolysis of the resulting mixture for R = Prⁱ has been investigated using O-17 NMR spectroscopy and the results can be interpreted in terms of the hydrolysis behaviour of the individual mononuclear components.

Solid state Ti and Zr phosphonates M(O₃PR)₂ are of interest for heterogeneous catalysis because of their layered structures.

Titanium

Zirconium

Hafnium

Further details

Group 5

Vanadium

Niobium

Tantalum

M(OR)₅ (M = Nb, Ta)

Further details

Group 6

Molybdenum

Tungsten

MO(OR)₄ (M = Mo, W)
We have determined the structures of a range of Group 6 oxoalkoxides and compared their solution behaviour to that of the Group 5 pentaalkoxides.

All of these compounds have edge-shared bioctahedral structures wiith bridging alkoxides, as shown for the cyclohexoxide WO(OCy)₄ below.

Further details

Main Group element alkoxides