Hexacoordinated silicon species: a possible model for reaction intermediates. 1. X-ray determination of the geometry in the solid state

Brelière, C.; Carré, Françis; Corriu, Robert J. P.; Poirier, Monique; Royo, G.; Zwecker, J.

doi:10.1021/om00109a046

Cited by 65 publications

(45 citation statements)

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“…In view of the virtually ideal angles in the proton sponge (7, average 120.4°) and the rather small angle in 8 (120.8°), this could be ascribed to a small ''size'' of the (CH 3 ) 2 N-group, i.e., (since the methyl groups are directed ''outwards'') a rather good compressibility of the lone pair orbital. In the silanes 1a,b (where the methyl groups reside in the same ''outward'' positions as in 2 11 ), this angle is larger than in 2 by 1.2°. The conclusion would be that the repulsive forces are stronger in 1a,b than in 2.…”

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confidence: 87%

“….'' 11 Dictated by the geometry of the DAN group, this is a matter of course and therefore is the case in 2, too. Table 2 shows that the alleged ''bond angles'' at Si (1a,b) involving N exhibit the same trends as the corresponding angles in 2, all of them being much smaller than an ideal tetragonal bipyramid (''elongated octahedron'') would require (apical/apical 180°, apical/equatorial and equatorial/ equatorial 90°).…”

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confidence: 99%

“…11 Of the quoted references, 30 the review of Voronkov et al 30b does not list comparable structures nor the quoted reference figures. These were obviously taken from the X-ray data of 11 (N-Si: 266 pm [31][32][33] ) and 12 (N-Si: 244 pm 32,33 ) and frame the value of a more closely related structure, 13 (N-Si: 258.4 pm 31,32,34 ).…”

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“…30b In a chromium carbonyl substituted 2-(dimethylaminomethyl)-phenyl silicon compound more closely related to 1a,b, 14, the dative bond from N to Si is even only 195.4 pm long. 36 The comparison with hexacoordinated silicon 11 rests on one compound which has a quite different structure, the two Si-N distances being 200.7 and 202.9 pm, 30c hence in the ''silatrane range'' rather than in the 244-266 pm range. Of the four N-Si distances in 1a,b, one is on the upper end of the latter (266.3 pm) and two even longer (268.0, 279.9 pm).…”

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Hexacoordinated carbon or tetracovalent silicon?

Schiemenz

Petersen

et al. 1998

Chirality

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Hexacoordinate silicon has been claimed to occur in bis(8-dimethylamino-naphth-1-yl)silanes on the basis of X-ray data and NMR spectra. Very much the same effects are shown by a bis(8-dimethylamino-naphth-1-yl)carbinol, pointing to essentially the same bonding in the Si and C compounds. Faced with the choice that either the carbon in the carbinol is hexacoordinate, too, or that the silicon in the silanes is, in fact, tetracovalent, we prefer the latter conclusion. Chirality 10: 180-189, 1998. © 1998 KEY WORDS: hypercoordinate silicon in naphthylsilanes; X-ray structures; NMR spectra; reinterpretationIn an ever-increasing number of papers, it is claimed that hypercoordination at the ''higher'' elements of the periodic table is a much more widespread phenomenon than previously believed.1 Some details, however, are puzzling. For example, in (8-dimethylamino-naphth-1-yl)-(''DAN'' 2 ) silanes, the step from conventional tetracovalency to pentacoordination and subsequent steps from there to hexa-, hepta-, and octa-coordination 3 are claimed to occur all with the same ease though in the realm of preparative organophosphorus chemistry, four P-C bonds at one P atom are easily formed, but the fifth and sixth only with increasing difficulty 4 and a seventh not at all. 5 In organosilicon as well as organophosphorus chemistry, penta-and hexacovalency are accomplished most readily when electronegative substituents cause a low electron density at Si/P whereas the recent claims of hypervalency often concern compounds where such substituents are lacking.6 Germanium and tin are believed to be as prone to hypercoordination, 7 though their orbitals, due to the larger size of these atoms, are more diffuse and hence geometrically less favoured for significant overlap with the filled orbital at nitrogen of a dimethylamino group. Within the frame of molecular orbital theory, it is hard to see where such atoms take all the orbitals from to achieve hexa-, hepta-, and octacoordination.8 MO theory, though often taken as a dogma, is no more than a theory used to describe facts and not a fact in its own merit, 9 and it is, therefore, legal to disregard it, but then, tetracovalency of carbon can no more be accepted as a dogma either, and it is, then, permitted to apply the same methods in search of hypervalent carbon.10 If, on the other hand, the dogma of tetracovalent carbon is retained, compounds of the same type, but with carbon instead of P, Si, Ge, Sn, etc., would provide a conclusive counter check whether the arguments brought forward in favour of hypervalency at these elements are indeed an iron-cast proof or not.In the first part of a wider program devoted to these problems, we deal with the DAN-silanes 1a-e (see Scheme 2) for which Corriu et al.11,12 believed to have found evidence for hexacoordination at Si. 2, which is a close analogon of 1b and, particularly, of 1c, was readily prepared by peri-lithiation of di(methyl)(naphth-1-yl)amine 13 and subsequent reaction with methyl formiate (yield 43%). We obtained an X-ray stru...

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Hexacoordinated carbon or tetracovalent silicon?

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Petersen

et al. 1998

Chirality

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“…It is noteworthy that X-ray structure analysis of the analogous silicon compound 38 [30] showed the same geometry.…”

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confidence: 72%

Hypercoordinate PII, PIII, and PIV Phosphorus Derivatives with Intramolecular Coordination by Donor Groups

Chuit

Reyé²

1998

Eur. J. Inorg. Chem.

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Dative N→P/Si Interactions — A Historical Approach [1]

Schiemenz¹

2002

Z. anorg. allg. Chem.

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The dative NǞSi/P interactions in 8-dimethylaminonaphth-1-yl-silanes and phosphorus compounds are largely an artefact which originated from insufficient perusal of the pertinent literature. Dative NǞP/Si Wechselwirkungen ؊ Eine historische Untersuchung [1]Inhaltsübersicht. Die dativen NǞSi/P-Wechselwirkungen in 8-Dimethylamino-naphth-1-yl-silanen und -phosphorverbindungen 1) Cases in which short distances d(N···Si/P) point to attractive interatomic interactions and in which the arrangement around Si/P has been described as (distorted) trigonal-bipyramidal or, in case of hexacoordination, as octahedral, are excluded from the following discussion. -van der Waals distances sind meist ein Artefakt als Folge der Nichtberücksichtigung der einschlägigen Literatur.

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Hexacoordinated silicon species: a possible model for reaction intermediates. 1. X-ray determination of the geometry in the solid state

Cited by 65 publications

References 1 publication

Hexacoordinated carbon or tetracovalent silicon?

Hexacoordinated carbon or tetracovalent silicon?

Hypercoordinate PII, PIII, and PIV Phosphorus Derivatives with Intramolecular Coordination by Donor Groups

Dative N→P/Si Interactions — A Historical Approach [1]

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