On the bonding properties of diphosphanylmethanide complexes with the group-14 elements silicon, germanium, tin, and lead in their divalent oxidationstates

The mono- and bidentate chelation of the main-group elements silicon, germa nium, tin, and lead through the phosphorus atoms of the diphosphanylmethani de ligand has been studied by means of quantum chemical methods. In accord with experimental investigations, the species are found to adopt a psi-tbp conformation of high flexibility. The various distortional modes causing th e axial and equatorial positions to become equivalent have also been invest igated. In addition, the bonding situations in the electronically related b is(diamino)- and the higher element homologue bis(diarsanyl)methanide ligan d systems have been studied. The bonding situation in the hitherto experime ntally unknown bis(diamino)methanide Ligands is predicted to be similar to that in bis(amidinate) complexes. An analysis of the electron distributions (natural bond orbital population analysis) in these compounds reveals that the central main-group element is positively charged and weakly chelated b y the surrounding ligands.