Crystal structure of a very hindered olefin: 1,1-diphenyl-2,2-di-t-butylethylene at –155 °C

Abstract

An X-ray crystal structure determination at –155 °C of 1,1-diphenyl-2,2-di-t-butylethylene, C₂₂H₂₈[monoclinic, space group C2/c, a= 32.703(3), b= 6.085(1), c= 20.747(2)Å, β= 122.40(1)°, Z= 8, final R0.049 for 3 777 independent reflections) shows the steric hindrance effect on bond distances, valence angles, and twist of the central double bond (24°). Mean single-bond distances are: C(sp²)–C(sp²) 1.504, C(sp²)–C(sp³) 1.574, and C(sp³)–C(sp³) 1.546 Å. Valence angles tend to narrow the hindrance of the t-butyl groups. The shortest 1.5-intramolecular contacts are C(Ph)⋯ C(Bu^t) 2.80 and C(Bu^t)⋯ C(Bu^t) 3.13 Å. Intermolecular contacts are as expected. The conformation of the isolated molecule should differ little from that found in the crystal.