Matrix isolation FTIR and DFT studies of methyl isocyanide-boron trifluoride complex

The FTIR spectra of CH3NC and BF3 as well as their isotopomers co-deposited in low temperature Ar matrices were recorded. We observed several new infrared bands absent in the spectra of each component. These bands were assigned to the 1:1 EDA complex of CH3NC and BF3 based on the DFT calculations at the B3LYP/6-311CCG** level. The vibrational assignments and frequencies of the observed bands are the NC stretching at 2319.9 cmK1, the BF3 degenerate stretching at 1203.8 cmK1, the BF3 symmetric stretching at 840.4 cmK1 and the BF3 symmetric deformation at 638.0 cmK1 for the CH3NCK11BF3 isotopomer. Although the BF3 symmetric stretching is infrared inactive for free BF3 of D3h symmetry, complexation with methyl isocyanide would have induced a structural change in the BF3 moiety and the activation of this mode. Apart from some numerical discrepancies, the observed frequency shifts on complexation were in good agreement with the results of DFT calculation. Therefore, the structure of CH3NC-BF3 in solid Ar would be similar to the optimized C3v geometry, which corresponds to the gas phase structure. q 2004 Elsevier B.V. All rights reserved