Structures of Solvated Hexaphenyldisiloxanes

Abstract

C36H30OSi2.2C6H 6 (1); Mr = 691"03, trigonal, space group R3, a/¢=11.325(4), cu= 26-738(6)A [aR = 11-054 (2) /~, aR=61.63(2) ], V =2969.86A 3, Z=3, J)~,=1.159gcm -3, /z= 0.93 cm-1, A(Mo Ka) = 0.71069/~, F(000) = 1098, T = 293 K, final R = 0.044 for 1293 observed reflections with I> 3o'(1). C36Ha0OSi2.2C7H8 (2); Mr = 719.08, trigonal, space group R3, a~ = 11.542 (4), cn = 26-735 (6)/~ [aR = 11"129 (2) A, aR = 62"47 (2) ], V =3084"41/~3, Z=3, Dx=1"161gcm -3, lZ= 0.91 cm-1, A(Mo Ka) = 0.71069/~, F(000) = 1146, T = 293 K, final R = 0-066 for 727 observed reflections with I > 30"(/). (1) and (2) are isotypic. The molecule has 3 symmetry with the phenyl groups in staggered conformation. It consists of a central fragment Si--O--Si along the crystallographic c axis being linear by an inversion center. The principal interatomic distances are d(Si---O) = 1-622 (1) and d(Si--C)- 1.899 (2) A in (1), and d(Si--O) = 1.620 (2) and d(Si--C) = 1-866 (6) A in (2). In (1) the anisotropic thermal displacement parameters for the O atom, however, indicate a deviation from the linearity of the Si--O--Si fragment caused by static or dynamic disorder. This deviation would yield d(Si--O) = 1.64 A and/3(Si---O--Si) = 163 °.