Structural, Spectroscopic and Theoretical Studies of (^tButyl-isocyanide)gold(I) Iodide

Abstract

The complexes ( t BuNC)AuCl and ( t BuNC)AuI 13 C-labeled at the isocyanide group were prepared and investigated by concentration-and temperature-dependent IR and NMR spectroscopy in dichloromethane solution. No indication for association of the molecules was obtained. The crystal structure of the iodide complex was determined by X-ray diffraction methods and shown to feature only monomers with extremely large intermolecular Au-Au contacts of 4.162Å, well beyond the sum of the van der Waals radii. It therefore appears that ( t BuNC)AuI is a rare example of a sterically non-hindered L-Au-X complex which shows no aurophilic interactions whatsoever. In a quantum-chemical analysis (at the local MP2 level) of the dimerization of the model compounds (MeNC)AuCl and (MeNC)AuI in various dimer geometries it was demonstrated that the energy-balance of the dimerization is very delicate and not dominated solely by contributions from correlation / relativistic (aurophilic) effects.

Theoretical Chemistry of Gold

“…Electrostatic interactions: At this point it should be pointed out that the electrostatic multipole interactions between the components of the crystal are present. Some cases were analyzed by Pyykkö et al122 An example in which these interactions override the aurophilic attraction are the methylisocyanide halides, [(MeNCAuX) 2 ]; X=Cl,I 148…”

Syntheses, crystal structures, reactivity, and photochemistry of gold(iii) bromides bearing N-heterocyclic carbenes

“…Despite the steric repulsion of the substituents in 1-and 3-position and the small energetic differences between a coplanar and perpendicular orientation of the imidazolyl rings, the coplanar arrangement is found more often, because p-backbonding contributions are more pronounced in a coplanar than in a perpendicular orientation. As we point out in a recent publication, 25 there are subtle effects defining the aggregation of NHC-Ag-complexes in the solid state: the competition between the neutral form (NHC)AgCl and the ionic form [(NHC) 2 29 ). Nevertheless, the energetic differences between the different aggregation types seem to be small and the aggregation is very sensitive to small changes in crystallization conditions and alterations of the substitution of the NHC-ligand.…”

Synthesis, Characterization and Luminescence of Silver(I) and Gold(I) Complexes Bearing a Diethyl Acetal Functionalized N-Heterocyclic Carbene

“…Taking into account the sum of the van der Waals radii of silver (3.44Å [13]) these distances are indicative of only weak or even insignificant attractive argentophilic interactions. Therefore, this aggregation might be governed mainly by Coulombic or multipolar interactions (e. g. quadrupole-quadrupole interactions which in certain cases can even outperform metallophilic interactions [14]). It should be noted that this aggregation pattern is frequently found for silver halide complexes bearing NHC ligands, but is rarely observed with other ligands [7].…”