Vibrational spectra of crystalline tetrakis(trimethylsilyl) silane(IV), Si[Si(CH3)(3)](4), at high pressures

Infrared and Raman spectra of crystalline tetrakis(trimethylsilyl)silane(IV ), Si[Si(CH3)(3)](4) (TTMSS), have been recorded at various pressures rangi ng from ambient to similar to 55 kbar with the aid of diamond-anvil cell (D AC). The vibrational data strongly suggest the occurrence of a phase transi tion at about 2-3 kbar, which appears to be associated mainly with a change in the rearrangement of the trimethylsilyl groups. The tetrahedral Si-Si-4 skeleton itself is not greatly affected by the application of high pressur es. The v(C-H) and v(Si-C) modes of the attached trimethylsilyl groups are, however, particularly sensitive to pressure and exhibit significant change s in their pressure dependences (dv/dp) in both the lR and Raman spectra. T he observed pressure dependences range from -0.61 to 2.28 cm(-1) kbar(-1). Differential scanning calorimetric measurements also indicate the occurrenc e of the phase transition fairly close to room temperature (-37.6 degreesC) . (C) 2001 Elsevier Science B.V. All rights reserved.