Hexaphenylcyclotrisiloxane, C36H30O3Si3, a redetermination

Abstract

Abstract. orthorhombic, P212~21, a=

Strained Metallastannoxanes−Ring-Opening Polymerization versus Retention of Six-Membered-Ring Structure

“…The conclusions drawn from NMR spectroscopy and molecular weight determinations concerning the ring size and Si−O−Sn connectivities in solution are confirmed by X-ray analysis. Compounds 1 , 2 , 4 , and 6 are six-membered rings which can be regarded as formal derivatives of cyclo -(Ph 2 SiO) 3 9a in which one Ph 2 Si unit is replaced by Sn[(CH 2 ) 3 NMe 2 ] 2 , Sn[(CH 2 ) 3 N(Me)CH 2 ] 2 , Sn[Cp(CO) 2 Fe] 2 , and Sn( t -Bu)[Cp(CO) 3 W], respectively. Eight-membered cyclo -stannasiloxane 3 is a formal derivative of cyclo -(Ph 2 SiO) 4 9b with two Ph 2 Si units being replaced by Sn[(CH 2 ) 3 NMe 2 ].…”

On the SiOSi angle in 1,2-di-tert-butyl-1,1,2,2-tetraphenyldisiloxane

“…Fig. 2 shows the values of SiO distances, along with the corresponding SiOSi angles, that have been determined for seven disiloxane molecules in the crystalline state at various temperatures, and, in addition (for the point at the extreme left), values for hexaphenylcyclotrisiloxane (Tomlins, Lydon, Akrigg & Sheldrick, 1985). The least-squares line calculated through the points, for which weights inversely proportional to the standard deviations were used, is represented by r= 1.6957-0.0004550 (0 in degrees).…”

“…It is interesting to note that the two butyl groups are not in the trans position with respect to the Si...Si direction, but assume the gauche conformation. The plane of the SiOSi moiety is not between the planes containing the Si(2)...Si (1) (a) Hexaphenylcyclotrisiloxane (Tomlins et al, 1985); (b) O(SiH3) 2 (Barrow et al, 1979); (c) OISi(CH3)3] 2 (Barrow et al, 1979); (d) O{Si[C(CHs)s](C6Hs)2} 2 (present paper); (e) methylpentaphenyldisiloxane (Voronkov et al, 1981) Glidewell & Liles, 1981). (Tomlins et al, 1985).…”

“…The plane of the SiOSi moiety is not between the planes containing the Si(2)...Si (1) (a) Hexaphenylcyclotrisiloxane (Tomlins et al, 1985); (b) O(SiH3) 2 (Barrow et al, 1979); (c) OISi(CH3)3] 2 (Barrow et al, 1979); (d) O{Si[C(CHs)s](C6Hs)2} 2 (present paper); (e) methylpentaphenyldisiloxane (Voronkov et al, 1981) Glidewell & Liles, 1981). (Tomlins et al, 1985). The interior angle of the four phenyl groups at the C-Si bond has an average value of 116.5 (2) ° in the present molecule.…”

Chiral cyclotrisiloxanes

“…Several crystal structures for 4 were reported and for those that crystallized in the monoclinic crystal system, P2 1 2 1 2 1 showed chirality. 12 As in the case of 1, the phenyl groups of 4 formed a three-blade propeller structure with either P or M chirality (Fig. 3).…”