W0014

Systematic Analysis of Metal 7-Coordination Sphere Geometry from Crystallographic Data. Jing Wen Yao^a, J.A.K. Howard^a, R. C.B.Copley^a and F.H. Allen^b, (a)Dept. of Chem., Univ. of Durham, Durham, DH1 3LE, UK, (b)CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK

A computational procedure using the valence angles of metal coordination sphere, which addresses the problems of dimensionality and atomic permutational complexity for higher coordination number (n >= 7), has been applied to all the examples retrieved from Cambridge Structural Database (CSD)¹.

In a systematic analysis of metal coordination sphere geometries, it is necessary to consider the topological symmetry so that all the possible permutation isomers are taken accounted like in the carbocycle systems². This symmetry gives rise to n! equivalent enumerations of the ligand atoms L for each ML_n sphere. 5040 such permutations need assigning to a 7-coordination complex. This results in a large size of multivariate matrix dataset and has restricted the application of systematic study only to the low coordination number.

Using the proposed computational procedure, a unique atomic enumeration representing a polyhedral form for each fragment can be effectively assigned. In this way, principal component analysis (PCA) and other multivariate analysis techniques can be applied to geometrical problem of ML₇ sphere. The PC-scatterplots and a one or two-dimensional mappings of multi-dimensional valence angle space reveal geometrical preferences, deformations from standard polyhedral geometries, and interconversions between polyhedral forms for all the observed ML₇ complexes.

[1] Allen, F. H. & Kennard, O., Chemical Design Automation News, 8,1, (1993).

[2] Allen, F. H., Howard, J.A.K. & Pitchford, N. A., Acta Cryst., B49, 910, (1991).