Continuous Shape Measures as a Stereochemical Tool in Organometallic Chemistry

The continuous shape measures of homoleptic organometallic compounds of the transition elements relative to the classical coordination polyhedra offer a tool for their accurate stereochemical description, including geometries along polyhedral interconversion pathways. The use of the centroid of π-bonded carbon atoms to define a coordination position allows us to show that polyhedral continuous shape measures may serve as excellent stereochemical descriptors for complexes with such ligands as olefins, alkynes, and allyls. Such an approach can be extended to treat π-bonded diolefins as bidentate ligands, defining their bite and establishing comparisons with classical chelating ligands such as diamines, carboxylates, and diketonates. The adequacy of considering the η5-coordinated cyclopentadienide ligand as occupying one or three coordination positions in the piano-stool [M(η5-Cp)L3] complexes is also discussed.