Chemical bonding and electronic localization in a Ga(I) amide

The electron density in a one-coordinate [Ga(I) N(SiMe3 )R] complex has been determined from ab initio calculations and multipole modeling of 90 K X-ray data. The topologies of the Laplacian distribution and the ELI-D match a situation having an sp(3) -hybridized nitrogen with a tetrahedral arrangement of two single σ-bonds (to carbon and silicon) and two lone pairs pointing towards gallium in a scissor-grasping fashion. The analysis of the Laplacian distribution furthermore reveals a ligand-induced charge concentration (LICC) in the outer core of gallium oriented directly towards the nitrogen atom, and thus in between the two lone pairs. These observations might suggest that the trigonal planar nitrogen geometry result from a dative GaN bond, in which the roles of the metal and the ligand have been reversed with respect to a "standard" metal-ligand interaction, that is, the metal is here electron-donating. The ELI-D reveals a diffuse and directional lone pair on gallium, suggesting that this complex could serve as a σ-donor.