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

Abstract

The FTIR spectra of CH 3NC and BF 3 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 CH 3NC and BF 3 based on the DFT calculations at the B3LYP/6-311++G** level. The vibrational assignments and frequencies of the observed bands are the NC stretching at 2319.9 cm −1, the BF 3 degenerate stretching at 1203.8 cm −1, the BF 3 symmetric stretching at 840.4 cm −1 and the BF 3 symmetric deformation at 638.0 cm −1 for the CH 3NC− 11BF 3 isotopomer. Although the BF 3 symmetric stretching is infrared inactive for free BF 3 of D 3 h symmetry, complexation with methyl isocyanide would have induced a structural change in the BF 3 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 CH 3NC-BF 3 in solid Ar would be similar to the optimized C 3 v geometry, which corresponds to the gas phase structure.