The assignment and validation of metal oxidation states in the Cambridge Structural Database

A methodology has been developed for the semi-automatic assignment and chec king of formal oxidation states for metal atoms in the majority of metallo- organic complexes stored in the Cambridge Structural Database (CSD). The me thod uses both chemical connectivity and bond-length data, via ligand donor group templates and bond-valence sums, respectively. In order to use bond- length data, the CSD program QUEST has been modified to allow the coordinat ion sphere of metal atoms to be recalculated using user-defined criteria at search time. The new methodology has been used successfully to validate th e +1, +2 and +3 oxidation states in 743 four-coordinate copper complexes in the CSD for which atomic coordinates are available in ca 99% of structures using one or other method, and both succeed for >86% of structures.