Matrix Infrared Spectroscopic and Theoretical Investigations of X2CX···MX and CX3-MX Provided in Reactions of Ag and Au with Tetrahalomethanes.

Abstract

Reactions of laser-ablated silver atoms with tetrahalomethanes have been carried out in excess argon, and the products were identified via examination of the matrix spectra and their variation on photolysis and annealing. While production of the insertion products (CX3-AgX) was evident in all Ag reactions, different sets of product absorptions were also observed in the higher frequency region (1260-720 cm-1). They increased on photolysis but decreased on annealing, opposite to the absorptions of the insertion products. They have been assigned to weakly bound complexes of CX3 and AgX (X2CX···AgX), which were generated in halogen abstraction by the metal atom from CX4. These Cl-mediated Ag complexes are only slightly higher in energy than the insertion products due to the d10s1 electron configuration of the group 11 metal. NBO analyses reveal that the CX3 radical is coordinated to an ionic species (Ag+Cl-) via electron-rich X. The product absorptions marked "m" in the previous Au + CX4 study also most probably originated from the weakly bound product, which is more stable than the methylidene (X2C-AuX2).