On the electronic structure of main group diazadiene complexes, with boron, aluminium, gallium and indium, a density functional evaluation

Homoleptic diazabutadiene complexes with the Group 13 elements boron, aluminium, gallium and indium are studied by means of density functional calculations. For the homologues with aluminium and gallium they are in accord with experiment and predict tetrahedrally shaped complexes with C-2v symmetry. For the boron compound the complexes are also tetrahedral, but the nitrogens in one ring system are slightly pyramidalised. For the indium homologue a totally different geometry is obtained from the calculations. Both rings are almost in one plane, slightly twisted towards each other. As a consequence the spin density of the unpaired electron in the doublet system for E = B, Al, Ga is located in one ring system while it is equally spread over both rings for E = In, with concomitant strong spin polarisation for the overall structure. The formal oxidation state of the central atom is compared with the results of a charge density analysis.