Molecular Structure of Sila-Heterocycles

Abstract

The present review provides a comprehensive survey on the molecular structure of silaheterocyclic compounds (silacyclopropanes, silacyclobutanes, silacyclopentanes, silacyclohexanes and derivatives with larger rings, as well as compounds with fused and unsaturated heterocycles). In a lot of cases the heterocycles include also heteroatoms other than silicon, however, all silaheterocycles under consideration contain only Si-C bonds. INTRODUCTIONThe results of the structural investigations of the organosilicon heterocycles were reviewed in 1989 [1], However, sila-heterocycles have been the subject of extensive studies over the last 10 years. Much attention has been focused on the synthesis and structural characterization both derivatives with small rings and the macrocyclic compounds. There has been also a considerable interest in the cyclic π-electronic systems containing the silicon atom. Much of this interest concerns the possibility of aromatic character for the silole anions and dianions. Recently the first neutral silaaromatic compound -2-silanaphthalene was successfully isolated and structurally characterized. Our review is an attempt to summarize and systematize the numerous papers scattered in literature on this subject.

Conformational behavior of 3,3-dimethyl-3-silathiane 1-oxide and its diastereomeric 2-methyl derivatives

“…These values are about half of that reported for the ring inversion of thiane 1-oxide 1 (14.2 kcal mol −1 ) [16]. The lower activation barrier for cis-4 as compared with that for 1 can be explained by an elongation of two endocyclic bonds and some ring flattening at a silicon that is characteristic of silacyclohexane derivatives [24][25][26].…”

MOLECULAR STRUCTURE OF ORGANOSILICON COMPOUNDS WITH Si-Fe, Si-Co AND Si-Ni BONDS

“…The introduction of strong electron acceptors (fluorine, chlorine, oxygen) on silicon substantially shortens the Si-F bond (2.216-2.291 A), for trialkylsilyl, disilanyl and polysilanyl derivatives the Si-F distances exceeding 2.30, 2.32 and 2.35 A, respectively. 1 (^-C 5 Me5)Fe(CO) 2 SiH 3 (« 5 -C 5 H 5 )Fe(CO) 2 SiCl3 (/7 S -C 5 H 5 )Fe(CO) 2 SiFPh 2 (77 5 -C 5 Me 5 )Fe(CO) 2 SiH 2 SiH3 (/7 5 -C 5 H 5 )Fe(CO) 2 SiMe 2 SiPh 3 (>7 5 -C 5 H 5 )Fe(CO) 2 SiCI 2 SiCl3 (/7 5 -C 5 Me 4 Et)Fe(CO) 2 SiMe 2 SiMe 2 CI (7 5 -C 5 H 5 )Fe(CO) 2 SiMe 2 GePh 3 b) (/7 5 [38] in which the iron atom is hexacoordinated. The iron atom in the cationic phosphenium complex 6 [37] has a normal piano-stool configuration with a cyclopentadienyl ligand bonded in an /^-fashion.…”

“…The germanium atom does not bridge the Co-Co bond symmetrically, it is displaced slightly from the Co 4 plane, the dihedral angle between the GeCoCo triangle and the Co 4 plane being 8.1°. Atom Si (2 ) symmetrically positioned between Co (2) and Co (3) is closer to Co (1) , and slightly further from Co (4) . Atom Si (1) is closer to Co (1) and Co (3) while further from Co (2) and Co (4) .…”

“…According to X-ray diffraction the gold complex 13 [47] has dimeric structure, as a result of additional Au-Au bonding and partial migration of the di(diphenylphosphino)methylene (dppm) (1) and Au (2) and Fe (2) and Au (1) each bridged by a dppm ligand, thus forming two unusual, twisted six-membered rings fused along the Au-Au edge. The coordination geometry of the iron atoms may be described as distorted octahedral with the Ρ and Si atoms trans to one another and the CO ligands in a merarrangement.…”

MOLECULAR STRUCTURE OF ORGANOSILICON COMPOUNDS WITH Si-M (M = Ge, Sn, Pb, Ti, Zr, Hf) BONDS

“…A pyramidalization of the germanium center in germole 13 is clear, as evidenced by the angle between the C 4 Ge and the Ge-Si bond of only 100. 1 The carbon part of the heterocycle has considerable diene character. The Si-Ge distance of 2.446 A is about 0.06 A longer than the Si-Ge distance in 1-tris-(trimethylsilyl)-2,3,4,5-tetramethylgermole C 4 Me4Ge(H)Si(SiMe 3 ) 3 [26] and 0.08 Ä longer than in compound 12.…”