Die Struktur des Tetraphenyldisiloxans

Structure of Tetraphenyldisiloxane Tetraphenyldisiloxane 1 crystallizes at 298 K monoclinically (P2₁/n; a = 1407.6; b = 610.7; c = 1262.7 pm; β = 95.87° Z = 2) and undergoes a second order phase transition at 200 K, in an almost unchanged structure of triclinic symmetry. At 298 K the molecules are already bent (Si? O? Si = 160°) with static or dynamical disorder of the bridging atom. Both Si? O distances are different (156 or 169 pm), because the shift of the bridging O atom is not perpendicular to the Si? to? Si vector. The reason for this remarkable behavior is not yet clear. According to the vibrational spectra, the Si? O? Si bridge is bent in the crystal but, in CCl₄ solution a dynamical oscillation through the linear configuration may occur.