Solutions of lithium tetrafluoroborate in N,N-dimethylformamide-acetonitrile and N,N-dimethyl-
formamide-tetrahydrofuran mixed solvents have been investigated by infrared and Raman spectroscopies. New bands, due to Li^＋ solvation, were detected in the region of the C＝O strectching, O＝C—N deformation and CH₃ rocking modes for N,N-dimethylformamide. The change in band for the co-solvents was weak. The number of N,N-dimethylformamide molecules in the first solvation shell of Li^＋ was calculated and the preferential solvation of lithium ion by N,N-dimethylformamide indicated. This result has been supported by our ab initio calculations.

Key words: lithium tetrafluoroborate, N,N-dimethylformamide, acetonitrile, tetrahydrofuran, vibrational spectroscopy