On the coordination in metal saccharinates. Implications for bond-order models of metal-ligand binding

The structures of saccharinates retrieved from the Cambridge Structural Dat abase were used to discuss the coordination properties of deprotonated sacc harin. The series of the first-row metal(II) saccharinato isomorphs and of triphenylstannyl saccharinates were analyzed within the bond valence model (BVM). The "relative radius" parameter of the saccharinato ligand for the M (Ow)(4)(Nsac)(2) type of coordination was estimated (1.424 Angstrom) from c orrelation of the metal-N(saccharinato) distances with the Shannon-Prewitt ionic radii. Making use of the exponential bond distance-bond order (BDBO) relation of P auling within the BVM, ligand-specific mean bond order slims (MBOS) were re cently derived for several ligands. Coupled with the coordination number (C N), they are predictive for the metal-ligand bond lengths. Using parameteri zed power function instead of the exponential form of the BDBO relation, a new set of MBOS's is derived here: isothiocyanate 2.56 +/- 0.06; pyridine 1 .84 +/- 0.16; imidazole 2.02 +/- 0.12; chloride 2.05 +/- 0.10; water 1.54 /- 0.03. The two sets of MBOS values can be used to predict the metal-ligan d distances nearly equally well, showing that the distances are solely pred etermined by the MBOS and CN values, independently of the particular form o f BDBO relation used.