Disorder in the Crystal Structures of Hexakis(dimethylsilyl)benzene and its Tricarbonyl Chromium, Molybdenum, and Tungsten Complexes

Bart Kahr, Jeffrey M. Chance, Kurt Mislow, Jeffrey M. Chance

Research output: Contribution to journalArticle

Abstract

The crystal structures of hexakis(dimethylsilyl)benzene (1) and its tricarbonyl tungsten (2), molybdenum (3) and chromium (4) complexes were determined by X-ray diffraction. Compound 1 crystallizes in the monoclinic system, space group P21/c with a = 11.196(5)Ǻ, b = 19.675(9)Ǻ, c = 24.447(8)Ǻ, Z = 8, at 175K. The metal complexes 2, 3, 4 are isomorphic; the compounds exhibit trigonal modifications (2t, 3t, 4t), space group R3 or R3, Z = 6. Crystal data: (2t) a = 19.044(5)Ǻ, c = 14.343(4)Ǻ, at 193 K; (3t) a = 19.056(4)Ǻ, c = 14.633(5)Ǻ, at 298 K; (4t) a = 19.047(5)Ǻ, c = 14.144(5)Ǻ, at 193 K. The metal complexes were dimorphic; compounds 2 and 3 exhibit monoclinic modifications (2m, 3m), space group P21 Z = 2. Crystal data: (2m) a = 11.059(4)Ǻ, b = 13.885(4)Ǻ, c = 11.140(3)Ǻ, β = 114.79(3)Ǻ°, at 225 K; (3m) a = 11.020(6)Ǻ, b = 13.838(4)Ǻ, c = 11.099(4)Ǻ, β = 114.54(3)°, at 193 K. Each of the five structures that were solved and refined (1, 2m, 2t, 3m, 4t) exhibit an orientational disorder. The extent of the disordering, measured as the refined occupancy of the minor species, varies for independent molecules within the same asymmetric unit in 1, and between isomorphic structures in the trigonal and monoclinic series of 2, 3, and 4. The disorder was accommodated differently in the trigonal and monoclinic modifications. The metal tricarbonyl units adopt a staggered conformation with respect to the side chains. Substantial out-of-plane deviations (>0.2 Ǻ) of the dimethylsilyl groups were observed in all the structures and arene bond alternations were measured in the metal complexes.

Original languageEnglish (US)
Pages (from-to)195-214
Number of pages20
JournalMolecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals
Volume210
Issue number1
DOIs
StatePublished - Jan 1 1992

ASJC Scopus subject areas

  • Condensed Matter Physics

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