Absence of halogen...halogen interactions in chlorotrimethylsilane polymorphs

Abstract

The structures of in situ pressure-frozen chlorotrimethylsilane crystals, (CH3)3SiCl, have been determined at 0.23, 0.30 and 0.58 GPa. The molecular arrangements in the low-temperature and high-pressure phases are two-dimensionally isostructural, but different in the third perpendicular direction. Consequently, a striking similarity exists between the unit-cell dimensions of these polymorphs. The absence of short Cl...Cl contacts, both in the low-temperature or pressure-frozen phases of (CH3)3SiCl, has been rationalized in terms of the favoured packing patterns and comparable energies of halogen...halogen interactions and other van der Waals forces.

High-pressure freezing, crystal structure studies and SiCF3 bond polarizability of trimethyl(trifluoromethyl)silane

“…The largest differences in unit-cell dimensions are in the b parameter, 1.69 Å longer, and in the b angle, 14.58 larger in (CH 3 ) 3 SiCF 3 than in (CH 3 ) 3 SiCl; the molecular packing is similar. Gajda et al [20] established, that in low-temperature phase a and high-pressure phase b of (CH 3 ) 3 SiCl the molecules are arranged head to tail in the manner avoiding short ClÁ Á ÁCl contacts. Likewise, there are no short contacts between CF 3 groups in the high-pressure (CH 3 ) 3 SiCF 3 phase.…”

High-pressure crystallography

“…On the other hand, these huge pressures are comparable to the intermolecular interactions in crystal structures. Molecular crystals are formed by a very large group of organic compounds and it has already been recognized that pressure is an efficient method of generating new polymorphs (Boldyreva, 1990(Boldyreva, , 2004Allan et al, 1998;Allan & Clark, 1999;Allan et al, 2002;Boldyreva, Shakhtshneider, Ahsbahs, Sowa & Uchtmann, 2002;Boldyreva et al, 2003;Fabbiani et al, 2005;Podsiadło et al, 2005Podsiadło et al, , 2006Gajda et al, 2006;Gajda & Katrusiak, 2007;Bujak et al, 2007) and binary systems characteristic for high-pressure conditions only (Loubeyre et al, 1993(Loubeyre et al, , 1994Loubeyre, 1996;Kuhs, 2004). The higher the pressure, the further-reaching are the structural modifications.…”

High-pressure diffraction studies of molecular organic solids. A personal view

“…Later, many examples were published in the papers by several groups (Fourme, 1968;Weir et al, 1969;Fourme et al, 1971;Allan et al, 1998;Allan & Clark, 1999a,b;Allan et al, 1999Allan et al, , 2001Allan et al, , 2002aKatrusiak et al, , 2007Podsiadło et al, 2005Podsiadło et al, , 2006Lozano-Casal et al, 2005;Gajda et al, 2005Gajda et al, , 2006Oswald, Allan, Day et al, 2005;Budzianowski et al, 2005;Budzianowski & Katrusiak, 2006a,b;Budzianowski et al, 2006;McGregor et al, 2006;Bujak et al, 2007;Dziubek et al, 2007;. Sometimes, the same polymorph is formed as a result of crystallization on cooling and with increasing pressure; examples are 1,2-dichloromethane (Podsiadło et al, 2005), and carbon disulfide .…”

“…The interest in these phases dates back to the work by Bridgman, who, in particular, compared the high-pressure and the low-temperature polymorphs of CCl 4 and CBr 4 (Bridgman, 1931). The analysis of the high-pressure forms as compared to the lowtemperature ones, as well as of the anisotropy of compression of the crystals with increasing pressure, makes it possible to reveal the structures, in which the halogen-halogen interactions can be considered as the main cohesive forces responsible for the molecular arrangements (Podsiadło & Katrusiak, 2006;Bujak et al, 2007), and the structures in which halogenhalogen interactions are not attractive at all Gajda et al, 2006). Very interesting information was obtained for series of substituted dihalomethanes (CH 2 XY, where X, Y = Br, Cl, I), 1,2-dihalotetrafluoroethanes X(CF 2 ) 2 Y (X = Br, I; Y = Br, I) and dichloroacetic acid, which show clearly systematic isostructural relations resulting from the specific intermolecular interactions in their pressure-crystallized phases (Podsiadło et al, 2006;Katrusiak et al, 2007).…”

“…One of the examples is water -ambient-pressure and high-pressure ices differ significantly in their structures and properties (Petrenko & Whitworth, 1999). Acetone (Allan & Clark, 1999b), acetic acid (Allan et al, 1999), alcohols (Allan et al, 1998(Allan et al, , 1999(Allan et al, , 2001, benzene (Fourme, 1968;Piermarini et al, 1969;Weir et al, 1969;Fourme et al, 1971;Budzianowski & Katrusiak, 2006a), chlorotrimethylsilane (Gajda et al, 2006), 1,2-dichloromethane (Podsiadło et al, 2005), sulfuric acid (Allan et al, 2002b), phenol (Allan et al, 2002a), 2-chlorophenol and 4-fluorophenol (Oswald, Allan, Day et al, 2005; are further examples of compounds, liquid at ambient conditions, which also give different polymorphs on cooling and with increasing pressure.…”