Si-Br bonds

The functionalization of poly(phen5isilane) [99936-07-9] by reaction with CCl and with CBr has also been reported (117). This yields polymers containing Si—Cl or Si—Br bonds, but leaves the Si—C H bonds intact. 

The observed Si—Br bond length in HjSiBr, 2.209 A, is 0,10 A less than the sum of the single-bond radii, 3.31 A. The predicted shortening for ionic character is 0.07 A the remainder, 0.03 A, corresponds to 8 percent of double bond character, approximately equal to the 7 percent bond-orbital release of the three H—Si bonds. Similarly,... 

Consideration of the X-ray structure (with a Si—Br bond distance of 2.479 A and average CSiC bond angles of 115.8°) and the relevant 29Si NMR shift of 529Si = 109.8 ppm indicate, however, that no R3Si+ species was observed, but rather a structure in which... 

The fact that in 64a the monodentate ligands are cis to each other, as has been found in numerous other hexacoordinate bis-acylimidato-7V,(9 chelates 30-38,43-50 suggests that in the absence of special constraints the cis orientation is preferred. It follows that the uncommon trans geometry, found in 65 and 66, is the result of steric repulsion between the bulkier Si-Cl and Si-Br bonds and the isopropylidene methyl group. All three dihalo-complexes (the cis-64 and trans-65 and 66) react readily with... 

The adopted vibrational frequencies are from the work of Clark and Rippon ( ), who recorded the Raman spectra in the vapor phase (210 C). The spectral data were interpreted in terms of a tetrahedral structure. This structure is consistent with the electron diffraction data of Lister and Sutton (6), Yamasaki et al. (7 ), and Spitzer et al. (8), which suggested a tetrahedral structure with a Si-Br bond distance of 2.15 0.02 A. We adopt this bond distance. The principal moments of inertia are I = Ip 163.5574X 10 g cm. Shimanouchi, in a recent compilation of molecular vibrational frequencies (9), suggested somewhat... 

Stannic bromide has been used as a selective brominating agent for silanes. Monosilane, disilane, and the methylsilanes Me3SiH4- (n = 1—3) all react to convert one Si—H bond into a Si—Br bond with no trace of... 

Sb-H bonds, 489 Sb-halogen bonds, 489 Se-H bonds, 451 Se-halogen bonds, 451 Si-Br bonds, 465 Si-Cl bonds, 464 Si-F bonds, 464 Si-H bonds, 455 Si-1 bonds, 465 Sn-Br bonds, 475-476 Sn-Cl bonds, 475 Sn-F bonds, 475 Sn-H bonds, 473 Sn-1 bonds, 476 Te-H bonds, 453 Te-halogen bonds, 453 Rare gas complexes anions, 1452 cations, 1446-1452 neutrals, diatomic, 1429-1436 polyatomic, 1436-1446 Rb-contarnmg species neutrals, 557-559 Rb clusters, 559-562 Rb clusters, 562-563 Re-containing species neutrals,796-799 Re clusters, 799-801 Re clusters, 801 Rh-contarnmg species neutrals, 882-892 Rh clusters, 892-894 Ru-containing species neutrals, 840-848 Ru clusters, 849-851... 

Se-O bonds, 452 Se-P bonds, 452 Se-S bonds, 452 Se-Se bonds, 451 Se-Te bonds, 452 Selenium clusters/complexes anions, 1346 cations, 1341-1346 neutrals, 1341 Si-containing compounds C-H bonds, 100, 131, 133 C-O bonds, 344 N-C bonds, 418 N-H bonds, 377 O-H bonds, 261, 304 0-0 bonds, 315 Si-Br bonds, 465 Si-C bonds, 460-462 Si-Cl bonds, 464-465 Si-F bonds, 463 -464 Si-Ge bonds, 467 Si-H bonds, 455-459 Si-1 bonds, 465 Si-Mn bonds, 467 Si-N bonds, 463 Si-O bonds, 462-463 Si-P bonds, 466 Si-S bonds, 466 Si-Se bonds, 450,466 Si-Si bonds, 459-460 Si-Sn bonds, 467 Si-Te bonds, 466 Silicon neutral complexes anions, 1153 cations, 1147-1152 neutrals, 1140-1147 Sm-containing species neutrals, 623 -626 Sm clusters, 626 Sn-containing compounds 0-0 bonds, 315 Sn-Br bonds, 475-476 Sn-C bonds, 476-477 Sn-Cl bonds, 475 Sn-F bonds, 475 Sn-Ge bonds, 475 Sn-H bonds, 473-474 Sn-1 bonds, 476 Sn-O bonds, 477 Sn-Pb bonds, 475 Sn-S bonds, 477 Sn-Se bonds, 477 Sn-Si bonds, 467 Sn-Sn bonds, 474-475 Sn-Te bonds, 477 Sr-containing species neutrals, 591-593 Sr+ clusters, 593-595 Sulfates... 

Vinyl groups bound to silicon will act as shielding groups, because addition of HBr or Br yields a Si—Br bond by (3-elimination [85]... 

It was assumed that the z axis coincides with the Si-Br bond, x is perpendicular to the molecular plane. Reference... 

Monoanionic bidentate chelators have also been shown useful to achieve hexa-coordination of silicon under retention of Si—Br bonds (Scheme 43) [135,154,157, 262, 336, 337]. Although the Si atoms were shown to be hexacoordinated in the solid state, for some of those compounds (e.g., 168, 169) ionic dissociation of the Si—Br bond was found to occur in solution. As for the above pyridine adducts, the Si—Br bond lengths exhibit noticeable variability (ranging between 2.33 and 2.45 A). 

The weakness of the Si—Br bond, which is reflected by its ionic dissociation upon silicon hexacoordination, is also manifested in neutral pentacoordinated Si complexes. As shown by the related compoimds in Scheme 44, the gradual approach of the additimial donor moiety (O atom) causes a stepwise dissociation of the Si X bond, which is reflected in the umbrella inversion of the equatorial Si-bound alkyl groups [338, 339]. In this course, a very long Si—Br bond (3.12 A) has been observed for 172. 

In the compounds 170-172, the halide (e.g., the Si—Br bond) occupies an axial positicai in the distorted trigOTial-bipyramidal Si coordination sphere (cf. compounds in Scheme 42). The features of both axial [95, 190] and equatorial Si—Br bond situatimi [270] in pentacoordinated bromosilicon complexes have recently been... 

Last but not least, a carbene adduct of SiBr4 (175) with pentacoordinated Si atom (with carbene ligand in equatorial position and Si-Br bond lengths of 2.24 and 2.38/2.41 A for equatorial and axial sites, respectively) [108] and a dinuclear pentacoordinated bromosiUcon compound (176) with a central Si2N2 four-membered cycle and rather short axial Si—Br bonds (ca. 2.28 A) [340] have been reported. 

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