Five-co-ordinated silicon compounds: geometry of formation by intramolecular co-ordination. Crystal structure of 2-(dimethylaminomethyl)phenyl-1-naphthylsilane

Abstract

Studies of a wide range of intramolecularly five-co-ordinated silicon compounds with chelating nitrogen donors have been made, with a view t o obtaining further information on the details of nucleophilic substitution reactions at silicon. The crystal structure of 2-(dimethylaminomethyl)phenyl-I -naphthylsilane has been determined b y single-crystal X-ray diffraction ( R = 0.074 for 564 observed reflections). Crystals are tetragonal, space group 14, with Z = 8 in a unit cell of dimensions a = 21.845(5) and c = 7.1 19(2) A. The central silicon atom shows essentially trigonalbipyramidal co-ordination, with the axial positions occupied by the naphthyl group and the donor nitrogen atom, and the t w o hydrogen atoms occupying equatorial positions. Comparison with other structures reported in the literature shows that this geometry, always with axial disposition of the donor atom, is generally adopted b y molecules of this type. Silicon-29, 19F, and 'H n.m.r. spectroscopic data for similar compounds with varying substituents on the silicon atom show that the same geometry is adopted by these intramolecularly co-ordinated species in solution.* This value was chosen as an average between the value previously reported for molecule (13) l 1 and other data from the literature (M.

Synthesis and reactivities of dihydrosilanes tethered with two thioether moieties

“…For example, {2-(Me 2 NCH 2 )C 6 H 4 }NpSiH 2 (Np = naphthyl) and (8-Me 2 N-1-C 10 H 6 )PhSiH 2 , the X-ray structures of which indicate five-coordinate trigonal bipyramidal structures [7,8], show signals at −47.3 and −44.1 ppm, respectively, in the 29 Si NMR spectra, whereas the 29 Si NMR spectrum of PhNpSiH 2 indicates a resonance at −35.6 ppm [8,9]. The 29 Si NMR spectra of dihydrosilanes 1a-c showed slight up-field shifts (δ Si = −41.3 ppm for 1a, −40.9 ppm for 1b, and −40.1 ppm for 1c) compared with that of Ph 2 SiH 2 (δ Si = −34.5 ppm) [10].…”

Darstellung, Eigenschaften und Reaktionsverhalten von 2-(Dimethylaminomethyl)phenyl- und 8-(Dimethylamino)naphthylsubstituierten Lithiumhydridosilylamiden - Bildung von Silaniminen durch Lithiumhydrideliminierung

“…Die Darstellung der Organolithiumverbindungen 2-Me 2 NCH 2 C 6 H 4 Li und 8-Me 2 NC 10 H 6 Li erfolgte entsprechend Literaturangaben durch Reaktion von n-BuLi (1,6 M Lo È sung in n-Hexan) mit N,N-Dimethylbenzylamin [31,32] bzw. 1-(Dimethylamino)naphthalin [33,34] in Diethylether.…”

Hexacoordinated carbon or tetracovalent silicon?

“…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 ). In all these structures, the claim of hypervalency rests on the same arguments as for 1a,b so that they are not suitable reference compounds.…”