Low frequency infrared spectra of acetonitrile and acrylonitrile derivatives of chromium, molybdenum and tungsten hexacarbonyls

Abstract

The infrared spectra of the complexes M(CO) 6- n (L) n (M = Cr, W; L = CH 3CN, n = 1, 2; L = CH 2CHCN, n = 1) and M(CO) 3(CH 3CN) 3 (M = Cr, Mo, W) in the CsBr region have been studied. The spectra of W(CO) 6- n (CH 3CN) n ( n =1, 2, 3) were investigated in the 400-100 cm −1 region, and whereas three very weak bands are observed in the spectrum of W(CO) 3(CH 3CN) 3 below 265 cm −1, the mono- and disubstituted derivatives exhibit no absorption bands in the 400-100 cm −1 region. For the mono- and disubstituted derivatives, all bands in the 700-265 cm −1 region arise from metal—carbon stretching, MCO bending and CCN bending; and no metal—nitrogen stretching bands could be assigned. However, for M(CO) 3(CH 3CN) 3 metal—nitrogen stretching vibrations are assigned at 552, 495 cm −1 (Cr); 533, 481 cm −1 (Mo); and 538, 489 cm −1 (W). The bands below 265 cm −1 in the spectrum of W(CO) 3(CH 3CN) 3 have been tentatively assigned to WNC bending modes.