Infrared Spectra of CX3-AuCl and CX2-AuCl2 Generated in Reactions of Laser-Ablated Gold Atoms with Chlorofluoromethanes and Carbon Tetrachloride

Laser-ablated gold atoms have been reacted with CF3Cl, (CF3Cl)-C-13, CF2Cl2, CFCl3, CCl4, and (CCl4)-C-13 in excess argon during condensation, and the CX3-AuCl (X = F, Cl) insertion products are generated. In the reactions of CFCl3 and CCl4 the methylidene complexes (CXCl-AuCl2) are also produced, and CFCl-AuCl2 is interconvertible with the insertion product CFCl2-AuCl upon photolysis. The tetrachloroauric insertion and methylidene complexes are energetically comparable and also structurally close to each other. These products reveal that C-Cl insertion by Au readily occurs, consistent with our previous Au investigations, and subsequent X migration also follows in case the methylidene is energetically reachable. The C-Au bonds of the insertion and methylidene complexes are comparable, unlike those of the previously studied transition-metal systems, and NBO results also show that the methylidene C-Au bond (B3LYP computed 2.04 angstrom) is a effectively a single bond. Evidently the gold atom with filled 5d and 4f orbitals cannot accommodate a g system for a methylidene-like complex without larger stabilizing/conjugating ligands on carbon.