Infrared spectroscopic and theoretical investigation of the matrix-isolated reaction products of small molecules with laser-ablated transition and actinide metal atoms.

摘要

Laser-ablated metal atoms react with CH3X (X = F, Cl, and Br) producing novel compounds, which are trapped in an inert argon matrix. C-X bond activation forms the primary CH3---MX insertion complexes, which is followed by alpha-H transfer to form the simple methylidene CH 2=MHX complexes. Products are identified by their infrared spectrum, vibrational shifts upon isotopic substitution (13C and D), and comparison to theoretical predictions. Computations suggest these complexes possess considerable agostic distortions, an unusual interaction between the central metal atom and the bonded C-H electron pair. Reactions between metal atoms and CH2X2 (X = F or Cl) activate C-X bonds and produce CH2=MX2 complexes after alpha-halogen transfer. In these instances, no agostic interactions are observed indicating electron lone pair repulsions are substantially strong enough to prohibit agostic bonding. Group 4 metal atom reactions with CHX3 (X = F or Cl) produce either stable methylidene or triplet HC÷MX3 complexes, and reactions with CX4 (X = F or Cl) create partially filled triple bonded methylidyne species of the form XC÷MX3 as the major product. Possible reaction pathways are explored in detail. Freon-11, 12, and 13 (CFCl 3, CF2Cl2, and CF3Cl) react with transition metal atoms to create analogous methylidyne complexes. Here, the FC÷MX 3 complexes are formed on deposition, and photoisomerize to the ClC÷MX 3 product on UV light irradiation. The reaction products that form with molecular CF3Br and CF3I are also discussed.