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, 13CF3Cl, CF2Cl2, CFCl3, CCl4, and 13CCl4 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 Å) is a effectively a single bond. Evidently the gold atom with filled 5d and 4f orbitals cannot accommodate a π system for a methylidene-like complex without larger stabilizing/conjugating ligands on carbon.