Crystal structure of syn-2,2′-bifenchylidene E at –120 °C

Abstract

An X-ray crystal structure determination at –120 °C of syn-2,2′-bifenchylidene E, (I)[orthorhombic, space group P2₁2₁2₁, a= 8.574(2), b= 9.568(2), c= 19.841(3)Å, Z= 4, direct methods, final R 0.050 for 2 129 independent reflexions] shows the effects of steric hindrance on bond distances, valence angles, and twist of the central double bond. Mean C(sp²)–C(sp³) single-bond distance is 1.565 Å, while the spread of C(sp³)–C(sp³)(Me) distances is 1.512–1.555 Å. Central bond-lengthening due to steric hindrance is not very apparent (1.349 Å). Valency-angle distortions relieve steric hindrance in methyl groups. The shortest 1,6-intramolecular contact between methyl group carbons is 3.145 Å. Intermolecular contacts are as expected.