Complementary bonding analysis of the N-Si interaction in pentacoordinated silicon compounds using quantum crystallography.

The N-Si interaction in two pentacoordinated silicon compounds is investigated based on a complementary bonding analysis, which consists of bonding descriptors from real space and orbital space. These are derived from X-ray wavefunction refinements of high-resolution X-ray diffraction data of single crystals and from isolated-molecule theoretical wavefunctions. The two pentacoordinated compounds only differ in one methylene group, so that the amino substituent is more flexible in one of the structures, hence probing the attractive or repulsive character of the N-Si interaction.

Covalency and Ionicity Do Not Oppose Each Other-Relationship Between Si-O Bond Character and Basicity of Siloxanes.

Covalency and ionicity are orthogonal rather than antipodal concepts. We demonstrate for the case of siloxane systems [R Si-(O-SiR ) -O-SiR ] that both covalency and ionicity of the Si-O bonds impact on the basicity of the Si-O-Si linkage. The relationship between the siloxane basicity and the Si-O bond character has been under debate since previous studies have presented conflicting explanations.

The Weakly Coordinating Tris(trichlorosilyl)silyl Anion.

Closely following the procedure for the preparation of the base-stabilized dichlorosilylene complex NHC ⋅SiCl reported by Roesky, Stalke, and co-workers (Angew. Chem. Int.

How to make the ionic Si-O bond more covalent and the Si-O-Si linkage a better acceptor for hydrogen bonding.

Variation of a bond angle can tune the reactivity of a chemical compound. To exemplify this concept, the nature of the siloxane linkage (Si-O-Si), the most abundant chemical bond in the earth's crust, was examined using theoretical calculations on the molecular model compounds H(3)SiOSiH(3), (H(3)Si)(2)OHOH, and (H(3)Si)(2)OHOSiH(3) and high-resolution synchrotron X-ray diffraction experiments on 5-dimethylhydroxysilyl-1,3-dihydro-1,1,3,3-tetramethyl-2,1,3-benzoxadisilole (1), a molecular compound that gives rise to the formation of very rare intermolecular hydrogen bonds between the silanol groups and the siloxane linkages. For theoretical calculations and experiment, electronic descriptors were derived from a topological analysis of the electron density (ED) distribution and the electron localization function (ELF).