INTRODUCTION

•	Conformation rearragements are well known in five coordinate species, involving interconversion between square pyramid and trigonal bipyramidal geometries. See R. R. Holmes, Acc. Chem. Res., 1979, 12, 257 and R. R. Holmes and J. A. Deiters, J. Am. Chem. Soc, 1977, 99, 3318.

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Four coordinate metals have a tendency to adopt one of two geometries: square planar or tetrahedral. However, these geometries can be affected by external factors, e.g. substituents, and thus not all metal complexes have idealised conformations. The geometries can be described using the four cis-ML2 angles as well as the two trans-ML2 angles. Clearly these would be expected to be around 90o and 180o respectively for square planar complexes while all angles would be around 109.5o for tetrahedral complexes.

•	The 3D search facility available in ConQuest can be used to facilitate the study of such systems and potential interconversion ‘transition states’.