1,1,2,2-Tetramethyl-1,2-disilacycloocta-3,7-diyne — structure and bonding properties of a highly strained cyclic diyne

Abstract

1,1,2,2-Tetramethyl-1,2-disilacycloocta-3,7-diyne (4) could be prepared by reaction of 1,8-dibromo-4,4,5,5-tetramethyl-4,5-disilaocta-2,6-diyne (9) with lithium in the presence of catalytic amounts of biphenyl. X-Ray investigations on single crystals of 4 revealed an almost planar structure adopting C_2v symmetry. The transannular distances between the pairs of carbon atoms in the triple bonds are 2.672 and 3.153 Å, respectively. The analysis of the He(I) photoelectron spectrum of 4 reveals a strong interaction between the in-plane π-orbitals of the triple bonds and the Si–Si σ-bond.