1,1,3,3-Tetra-tert-butyl-2,2-diisopropyl-4,4-diphenyl­cyclo­tetra­silane

The molecule in the structure of the title compound, C₃₄H₆₀Si₄, lies on a twofold rotation axis that passes through the two Si atoms, resulting in a planar cyclo­tetra­silane ring. The dihedral angle between the cyclo­tetra­silane ring and the phenyl ring is 68.20 (5)°. The Si-Si bonds [2.4404 (8) and 2.4576 (8) Å] are longer than a standard Si-Si bond (2.34 Å) and the C-Si-C bond angle [97.07 (14)°] of the phenyl-substituted Si atom is smaller than the tetra­hedral bond angle (109.5°). These long bonds and small bond angle are favorable for reducing the steric hindrance among the bulky substituents.

anti-2,2,3,3,6,6,7,7,10,10,11,11,14,14,15,15-Hexadeca­methyl-2,3,6,7,10,11,14,15-octa­silapenta­cyclo­[10.4.2.2^4,9.0^5,8.0^13,16]icosa-1(17),4,8,12(18),13(16),19-hexa­ene

The title compound, C₂₈H₅₂Si₈, was synthesized by condensation of two mol­ecules of 1,2,3,4-tetra­kis­(chloro­dimethyl­sil­yl)benzene with lithium. The 3,4-disila-1,2-benzocyclo­butene rings in the centrosymmetric molecule are bridged by 1,1,2,2-tetra­methyl­disilanylene chains with an anti conformation. The benzene rings are deformed by fusion with a 3,4-disilacyclo­butene ring resulting in a slight boat conformation. Two Si-C bonds are bent to reduce the steric repulsion between the methyl groups on the two Si atoms and the methyl groups on another two Si atoms.