Oxygen-silicon bonds lengths

The structures of these oxidation products were confirmed by X-ray crystallography (Fig. 11). The oxygen atom of 8 connects two bridgehead silicon atoms with a Si-O bond length of 1.683(4) A and a Si-O-Si bond angle of 120.2(4)°. The Si-O bond length is somewhat longer than those of... 

Baur W. H. (1978). Variation of mean Si-O bond lengths in silicon-oxygen tetrahedra. Acta Cryst, B34 1754-1756. 

Figure 3.7 Molecular structure of [(Cp )Ca N(SiMe t)2l(thf>l calcium, nitrogen and silicon atoms are shown as black spheres, oxygen and carbon atoms are white. Selected bond lengths Ca-N 2.30(1), Ca-O 2.35(1), Ca-M 2.397A...

Figure 3.10 The structure of [BalNiSiMc il hlthfi ] Barium and nitrogen atoms are shown as black spheres, silicon atoms are grey and carbon and oxygen atoms are white. Selected bond lengths Ba-NI 2.587(6), Ila i 2 2.596(6), Ba-OI 2.745(6), Ba 02 2.717(6)A...

At that time the calculated Si—O bond length was 1.64(3) A. In 1989, Sheldrick15 indicated in his review that the additional data available at the time he wrote his review confirmed this finding. This value is smaller than the Stevenson-Schomaker corrected sum of the covalent radii of silicon and oxygen (1.76 A). The large amount of XRD structural data available today enables more accurate statistical analysis and the ability to verify it by theoretical calculation. 

The 3276 bond lengths obtained by XRD have been used to calculate the average Si—O bond length in compounds containing tetracoordinate silicon atom bonded to a dicoordinate oxygen atom. The average Si—O bond length is 1.629 A (s.d. 0.03 A, s.m. 

FIGURE 15. Histograms of Si—O bond lengths (left) and Si—O—X (X / Si) (right) in compounds with tetracoordinate silicon and dicoordinate oxygen atoms... 

TABLE 20. Si—O bond lengths in compounds with tetracoordinate silicon and hexacoordinate oxygen atoms... 

The sum of the covalent radii3 for silicon and sulphur is 2.21 A. The electronegativity of the sulphur atom is smaller than that of its congener oxygen atom and therefore the expected polarization and ionicity of the Si—S bond is smaller than that of the Si—O bond. As a result it is expected that the shortening of the Si—S bond length from the sum of covalent radii will be significantly smaller than that observed for the Si—O bond. 

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