Structure of the dimethylsilylamine pentamer, (C2H9NSi)5. A redetermination

Blake, Alexander J.; Ebsworth, E. A. V.; Welch, Alan J.

doi:10.1107/s0108270184006156

Cited by 21 publications

(8 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is a consequence of the sites that the two nitrogen substituents occupy around the silicon atom (axial and equatorial in the dimer and all axial in the pentamer), according to the hybridization picture provided by the NBO analysis. The different aggregation mode of Me 2 NSiH 2 Cl (as dimer) and Me 2 NSiH 3 (as pentamer) is explained as a structural requirement, as has been pointed out in the literature. , …”

Section: Discussionmentioning

confidence: 61%

“…As we have mentioned above, Me 2 NSiH 2 Cl crystallizes as dimer 5 , and the two-monomer units are held together by two dative Si ← N bonds in the solid. , In dimer 5 , the coordination around the silicon atoms is bipyramidal, with the long (2.06 Å) and short (1.81 Å) Si−N bonds in the axial and equatorial positions, respectively. Substitution of the Cl atom by H leads to an important change in the solid state where Me 2 NSiH 3 crystallizes as a pentamer ( 6 ). , In 6 the coordination of the silicon is also bipyramidal, but the nitrogen atoms occupy the two axial positions and the two Si−N bond distances are equivalent (1.98 Å). For both structures, we have only carried out DFT single-point calculations at the crystal geometries.…”

Section: Resultsmentioning

confidence: 99%

“…For example, Me 2 NSiH 2 Cl crystallizes as a dimer 5 , − in which both units are held together by two dative Si ← N bonds and the Cl atoms occupy axial positions. The non-chlorinated Me 2 NSiH 3 is aggregated in a completely different mode in the solid state: it forms a pentamer ( 6 ). , In this case, the three H atoms bonded to silicon occupy equatorial sites and all N atoms occupy axial sites. The crystal structure of 6 indicates that all silicon−nitrogen bond lengths in the 10-membered ring are equivalent and equal to 1.98 Å.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Inductive Effects in Neutral Pentacoordinated Silicon Compounds Containing a Si ← N Dative Bond. A Theoretical Study

et al. 1999

View full text Add to dashboard Cite

Using ab initio MP2 and DFT calculations, we have studied the structure of a series of pentacoordinated silicon compounds containing a Si r N dative bond and the influence of inductive effects on the Si r N bond. The study includes two series of model systems, namely, Si(NH 3 )X n Y 4-n (X ) OH, Y ) H or CH 3 ; n ranging from 0 to 4) and Si(NH 3 )(NH 2 )H 2 X (X ) Cl or H), methyl(2,2′,2′′-nitrilotriethoxy)silane, methyl(2,2′,3-nitrilodiethoxypropyl)silane, 8-(trifluorosilylamino)quinoline, 8-(trimethylsilylamino)quinoline, a dimer of Me 2 NSiH 2 Cl, and a pentamer of Me 2 NSiH 3 . All these structures have dative Si r N bonds. The nature of the bonds was analyzed using the Laplacian of the charge density distribution and the natural bond orbital (NBO) partitioning scheme. The calculations show that the dissociation energy of the Si r N dative bond in the model systems is always lower than 9 kcal mol -1 and that the Si r N bond length gets shorter as the number of electron-withdrawing groups linked to silicon increases. The different aggregation mode between the dimer of Me 2 NSiH 2 Cl and the pentamer of Me 2 NSiH 3 is also analyzed.

show abstract

Section: Discussionmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Inductive Effects in Neutral Pentacoordinated Silicon Compounds Containing a Si ← N Dative Bond. A Theoretical Study

et al. 1999

View full text Add to dashboard Cite

show abstract

“…There are many very pronounced differences in the chemistry of carbon and silicon compounds, and these differences are perhaps best reflected in a comparison of simple methyl and silyl analogues with the C/Si atoms solely substituted by hydrogen (CH 3 /SiH 3 ). Classical examples are dimethyl ether versus methoxysilane and disiloxane, , trimethyl- versus dimethyl(silyl)- and trisilylamine, methyl- versus silylhydrazines , and -hydroxylamines, , neopentane versus tetrasilylmethane, methylated versus silylated ylides, dimethyl- versus disilylnaphthalines, or finally hexamethyl- versus hexasilylbenzene …”

Section: Introductionmentioning

confidence: 99%

Synthesis, Properties, and Structure of Poly(silyl)pyridines. The Phantom of Intramolecular Si−N Bonding

1998

View full text Add to dashboard Cite

2-and 3-silylpyridine (2, 3) have been prepared from the corresponding bromopyridines either directly by metathesis reaction with KSiH 3 or via the lithiated pyridines and their reaction with halosilanes (in poorer yield). 3-Silylquinoline 4 was obtained from 3-lithioquinoline and tetra(ethoxy)silane followed by reduction with LiAlH 4 . 4-Silylpyridine ( 5), 2,6-disilylpyridine ( 9), 5/6-methyl-2-silylpyridine (6, 7), and 2-bromo-6-silylpyridine (8) were also obtained via the KSiH 3 route, and traces of pentasilylpyridine (15) have been detected among the products of the analogous reaction with pentabromopyridine. These compounds and the di-and tripyridylsilanes 10-13 have been characterized by their analytical and spectroscopic data. The crystal structures of 6, 9, and 5-methyl-2-trimethylsilylpyridine ( 16) have been determined by low-temperature ("in situ") X-ray diffraction techniques. In all cases the silyl substituents in the 2-position show bending toward the nitrogen atom of the ring (with angles N-C-Si much smaller than 120°), suggesting a coordinative bonding of nitrogen to silicon. The structures are in excellent agreement with results of ab initio calculations (MP2/6-31G*) carried out for 2-silyl-, 3-silyl-, and 2,6-disilylpyridine. These calculations indicate, however, that the distortions are not due to direct (exocyclic) Si-N donor-acceptor bonding (as also suggested in the literature for trimethylsilylpyridines), but originate from the changes in the electronic configuration of the heterocycle (as compared to benzene). This conclusion is supported by a review of structural data for methylpyridines and finally for pyridine itself: all these compounds show small N-C-X angles (X ) H, C, Si in ortho-position to N) and similar distortions of the heterocycle. Ab initio quantum chemical calculations for pyridine (in the literature) and for 2,6-dimethylpyridine (this work) further corroborate the findings for these analogues. In summary therefore, there is no special "silicon effect" in the molecular and electronic structure of ortho-silylated pyridines. The physical properties of the compounds are best interpreted through the effect of the heteroatom N on the structure of the arene ring. In the crystal structures there is also no evidence for intermolecular donor-acceptor interactions, e.g., as described for the pentameric [Me 3 Si-NH 2 ] 5 .

show abstract

“…t Presently Vice-Chancellor, University of Durham, Old Shire Hall, Durham DH1 3HP, England. taining Si--N bonds, such as trisilylamine (Barrow & Ebsworth, 1984) and dimethylsilylamine (Blake, Ebsworth & Welch, 1984a). These two compounds may be taken as representing two extremes: the former shows little if any difference between its gas-phase and solid-state structures, while the latter is monomeric in the vapour (Gundersen, Mayo, Rankin & Robertson, 1984) but forms a unique cyclic pentamer in the crystal.…”

Section: Introductionmentioning

confidence: 99%