Molecular structure of 1,1,8,8-tetramethyl-1,8-digermacyclotetradecane: the first 14-membered germacycles

Abstract

An X-ray crystallographic analysis indicated that 1,1,8,8-tetramethyl-1,8-digermacyclotetradecane exists exclusively as the [3434] conformer with germanium atoms at corner sites in the crystalline state. Molecular mechanics calculations (MM2) of 1,8-digermacyclotetradecane and germacyclohexanes showed that small C–Ge–C bond angle and C–Ge–C–C dihedral angle are characteristic of germacycles ranging from 14-membered to 6-membered rings. This tendency is also expected for the acyclic system when the C–Ge–C–C moiety is in the gauche conformation.