Conformational Preferences of 1,3-Diferrocenyl-1,1,3,3-tetramethyldisiloxane and Its Cocrystal with Ferrocene:  A Theoretical and Crystallographic Study of the Role of Intra- and Intermolecular Interactions

Abstract

The solid-state structure of 1,3-diferrocenyl-1,1,3,3-tetramethyldisiloxane (1) exhibits significant differences between the pure crystal and the cocrystal with ferrocene. The structure of (1) shows that the two silicon atoms have eclipsed constituents when viewed along the Si−O−Si linkage. The structure of 1,3-diferrocenyl-1,1,3,3-tetramethyldisiloxane·ferrocene (2) indicates that the siloxane now exhibits a staggered conformation when viewed along the Si−O−Si linkage. To understand the origin of these differences, a nonempirical study of the energetics of very large clusters, as models of the solid state, was undertaken. PRDDO/M calculations of the relative energetics of the two different conformers of 1 show that methyl−methyl steric interactions dominate the conformational energetics and that the monomer is ∼5 kcal/mol more stable in the staggered form found in the cocrystal. However, a detailed analysis of intermolecular interactions in the pure- and cocrystals demonstrate that intermolecular interactions are more favorable in the pure crystal than in the cocrystal, resulting in the high-energy eclipsed form of the monomer being stabilized. The importance of intermolecular interactions are evaluated by calculating insertion energies of a central monomer into large clusters of molecules derived from the full lattice. The role of specific intermolecular interactions, such as ferrocene−ferrocene, ferrocene−tetramethyldisiloxane, etc., are also investigated by a similar procedure, in which either the bridge or the ferrocene components of the lattice are removed. We find that the stabilization of the eclipsed form of the monomer in the pure crystal is due dominantly to intermolecular interactions between the tetramethyldisiloxane bridges and the neighboring ferrocenes.

Investigation of Molecular Interactions in the Carboxylato Zn(II) and Cd(II) Macrocyclic Complexes

“…These are comparative to those reported for related ferrocene compounds. 28,29 The rotational angle between the two Cp rings in 1 is close to 46.7 o (measured by C(11)-Cp (centroid)-Cp (centroid)-C(8)). Another pertinent structural feature found in 1 is that each 1D chain is linked together via hydrogen bonds.…”

“…These are also similar to those found in the complex 1 and other related ferrocene complexes. 28,29 The rotational angle between the two Cp rings in 1 is close to 7. Table 3).…”

Influence of Solvent in Crystal Engineering: A Significant Change to the Order–Disorder Transition in Ferrocene

“…[13][14][15][16] The literature on ferrocene co-crystals and solvates consists of studies on true ferrocene adducts [17][18][19][20] and on ferrocene derivatives. [21][22][23] Pertinent to this study are those involving co-crystals of FeCp 2 with fluoronated aromatics, e.g. decafluorobiphenyl, 17 octafluoronaphthelane, 18 and decafluorophenanthrene, 19 and nonfluoronated aromatic molecules such as pyrene.…”

“…The literature on ferrocene cocrystals and solvates consists of studies on true ferrocene adducts − and on ferrocene derivatives. − Pertinent to this study are those involving cocrystals of FeCp 2 with fluoronated aromatics, e.g., decafluorobiphenyl, octafluoronaphthelane, and decafluorophenanthrene, and nonfluoronated aromatic molecules such as pyrene . In the latter, the structure is characterized by a side-on interaction between both Cp rings and the plane of the pyrene molecule.…”

Natural cocrystallisation of two ferrocenyl compounds

“…Earlier in 1998, Marynick and co-workers reported that recrystallisation of a 1:1 mixture of ferrocene and 1,3diferrocenyl-1,1,3,3-tetramethyldisiloxane yields the 1:1 cocrystal of the two compounds. 10 This cocrystal has orthogonal orientations of the ferrocene moieties as found in the crystal of pure ferrocene. The intermolecular interactions are so favoured in the cocrystal that all the ferrocene moieties are in the high energy eclipsed conformation.…”