Quantifying donor-dependent relationships between geometric parameters of chelating ligands.

Two new pseudo-octahedral Ir(III) bis-NHC complexes reveal how coordination geometry affects ligand conformation. Comparison with their pseudo-square-planar Ir(I) analogues prompted us to identify and quantify an inverse relationship between the α and chair angles. Analysis of crystallographic structures from the CSD demonstrates its broader applicability and reveals distinct relationships for C- and N-donor ligands.