title: Experimental charge density analysis of a gallium(I) N-heterocyclic carbene analogue.
abstract: The experimental electron density of the only known example of a four-membered Ga(I) N-heterocyclic carbene analogue has been determined by multipole modeling of 90 K X-ray diffraction data and compared to theoretical data. In order to obtain a satisfactory model, it is necessary to modify the radial dependency of the core electrons of Ga using two separate scaling parameters for s,p- and d-electrons. Evidence for significant lone-pair density on Ga is found in the electron density and derived properties despite the partial positive charge of this atom. Static deformation density and molecular electrostatic potential clearly show a directional lone pair on Ga, whereas the Laplacian of the total electron density does not; this feature is, however, present in the Laplacian of the valence-only density. The Ga center also acts as an acceptor in four intramolecular C-H···Ga contacts, whose nature is probed by density properties. Substantial covalent character is apparent in the Ga-N bonds, but no sign of donation from filled N p-orbitals to empty Ga p-orbitals is found, whereas π-delocalization over the organic ligand is evident. This study highlights the utility of experimental charge density analysis as a technique to investigate the unusual bonding and electronic characteristics of low oxidation state/low coordinate p-block complexes.
authors.affiliation: Department of Chemistry & Centre for Materials Crystallography, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark. jacobo@chem.au.dk
authors.forename: Jacob
authors.initials: J
authors.lastname: Overgaard
authors.forename: Cameron
authors.initials: C
authors.lastname: Jones
authors.forename: Deepak
authors.initials: D
authors.lastname: Dange
authors.forename: James A
authors.initials: JA
authors.lastname: Platts
mesh_terms: D005708:Gallium / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; C030011:carbene; D005708:Gallium; D008697:Methane