THE FIRST SPECTROSCOPIC OBSERVATION OF AN EQUILIBRIUM BETWEEN A DIGERMENE AND GERMYLENES AND EXPERIMENTAL-DETERMINATION OF A BOND-DISSOCIATION ENERGY OF A GE-GE DOUBLE-BOND

An extremely hindered digermene (E)Tbt(Mes)Ge=Ge(Mes)Tbt (2; Tbt = 2,4 ,6-tris[bis(trimethylsilyl)methyl]phenyl; Mes = mesityl) was synthesiz ed. The temperature dependent change of UV-vis absorptions of 2 in sol ution indicated the quantitative interconversion between 2 and the cor responding germylene 3. The thermodynamic parameters (Delta H = 14.7 /- 0.2 kcal mol(-1) and Delta S = 42.4 +/- 0.8 cal mol(-1) K-1) (1 cal = 4.184 J) for the dissociation of digermene 2 to germylene 3 were ob tained from temperature dependence of the absorptions of 2.