C-H—-it interaction

Figure 53. The structure of Ni(S2COEt)2PPh3 (a) molecular structure, and (b) chain formation, via C—H- -it interactions, along the b axis.

Evidence for the weak hydrogen bond nature of C—H it interactions has been reported recently by Madhavi et al. in a study of the complexes of 2,3,7,8-tetraphenyl-l,9,10-anthyridine 26 with toluene and chlorobenzene [56]. It was found that diffraction quality crystals of 26 could not readily be obtained from common solvents, with the exception of toluene, which produced a 1 1 solvate,... 

Figure 3.9.11 Supramolecular chain-like arrays mediated by complimentary Sn... n and C-H. ..it interactions in the structure of 16...

This molecular recognition motif is not observed in cationic complexes showing 1 1 diastereoisomer cocrystallization, probably due to the effect of the counterion or solvent molecules in the crystal lattice [109,110]. As an example. Figure 3.19 shows hydrogen bonds and C—H it interactions in the crystallized 1 1... 

The structure of the 1 1 methanol solvate of olanzapine has been reported, where pairs of olanzapine molecules form a centrosymmetric dimer by means of C—H—-7t interactions [66]. The solvent molecule was linked to the drug substance through O—H-N, N—H O, and C—interactions. In a new polymorph of the 1 1 dioxane solvatomorph of (+)-pinoresinol, the structure was stabilized by O—H O hydrogen bonds between the compound and the solvent [67], Two new polymorphs of 2-cyano-3-[4-(/Y,jV-diethylamino)-phenyl]prop-2-enethioamide and its acetonitrile solvatomorph have been characterized [68], Although crystallization of the title compound was conducted out of a number of solvents, only the acetonitrile solvatomorph could be formed. 

This [(Cr)C-H]( ) [0](-) interaction between anions along the chain has been investigated by means of theoretical ab initio calculations [34]. It has been shown... 

The first step is coordination of the ethylene through its n orbital. The ethylene is trans to Cl with the C=C bond in the Cl-Ru-H plane. Facile migratory insertion (AE = 7.6 kcal.mol 1) of the coordinated ethylene in the Ru-H bond leads to an alkyl intermediate 6.2 kcal.mol 1 less stable than the n ethylene complex. The alkyl intermediate has a strong P C-H agostic interaction as illustrated by the unusually long agostic C-H bond (1.221 A) which helps to stabilize the unsaturation in the formally 14-electron alkyl intermediate. 

On several occasions, a different model has been proposed to account for the bridge bonding in metal alkyls. In this model, it has been suggested that the bridge involved 2 atoms with an M—C—H—M interaction ... 

The methylene isomer 15 eliminates carbon monoxide when heated at 110°C (toluene, xylene 24 h), and yet another carbon-metal hydrogen shift takes place (75). The methylidyne species 16formed in this irreversible reaction has been characterized by its NMR spectra [S(CH) 9.36, quartet (76) 8(CH) 118.4 (CD3)2CO (77)] which implies a structure analogous to the previously known ethylidyne derivative (/i.-H)3(/i.-CCH3)-Os3(CO)io (138). NMR data obtained for partially deuterated samples of the methyl complex 14 have yielded evidence that the methyl ligand occupies an unsymmetrical bridging position between two metal centers, a coordination mode which implies significant C H Os interaction... 

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