The Raman Spectrum of Liquid Diborane

摘要

The Raman spectrum of B2H6(l) is found to contain an isotopic triplet (v1) 793, 806, 821 cmmdash;1, a broad line (v2?) 1108 cmmdash;1and a very intense doublet (v3?) 2102, 2523 cmmdash;1as well as several weaker lines. Abnormally large values for the Bsngbnd;B, Csngbnd;C, and Sisngbnd;Si bond force constants in B2H6, C2H6, and Si2H6suggest that these bonds are compressed in these molecules by forces which may be associated with those which restrict internal rotation. The value of 55.3plusmn;1.5 cal./deg. is calculated for the entropy of B2H6(g) at 25deg;. Combined with the known heat of formation this value leads to a free energy of formation of mdash;30,000plusmn;4000 cal. for B2H6(g) at 25deg;. This large value does not truly indicate high stability, for diborane decomposes easily to form other boron hydrides.