I. V. Borisova

Synthesis and structure of tetrakis[bis(trimethylsilylmethyl)tin]

The synthesis of tetrakis[bis(trimethylsilylmethyl)tin] from the corresponding dihydride [(CH 3 ) 3 SiCH 2 ] 2 SnH 2 and the diethylamino derivative [(CH 3 ) 3 SiCH 2 ] 2 Sn[(C 2 H 5 ) 2 ] 2 is described. The title compound has undergone full X-ray structure analysis. Crystals of C 32 H 88 Si 8 Sn 4 are monoclinic, a 12.350, b 14.515, c 15.951 A, γ 97.54°, Z = 2, space group P 2 1 / n . The molecule comprises a centrosymmetric square Sn 4 cluster, with Sn—Sn distances of 2.839 and 2.834 A. The final R factor is 0.029.

Divalent silicon, germanium, and tin compounds with element--heteroatom bonds

Principal results and trends in chemistry of organic derivatives of divalent silicon, germanium, and tin containing bonds between these elements and the halogen, nitrogen, oxygen, and sulfur atoms are briefly surveyed. Selected characteristics of compounds with the element--phosphorus and element--arsenic bonds are discussed for comparison. Data on the synthesis and structures of new types of these compounds, viz., germanium(ii) diacylates, the alkoxy derivatives E14(OR)2 and E14(OR)Y (E14 = Ge, Sn; R = Me2NCH2CH2; Y = Cl, AcO, (Me3Si)2N), and the ate-complexes Li(+)[E14(OCH2CH2NMe2)3](–) and [Li(thf)2](+)[TsiE14(SBu)2](–) (E14 = Ge, Sn; Tsi = (Me3Si)3C), are presented. It was established for the first time that germanium(ii) and tin(ii) derivatives can be stabilized in the monomeric form only through the intramolecular Nsp3→E14 coordination bonds and the σ-acceptor effect of the oxygen atoms without introduction of bulky substituents.

Alkaline hydrolysis of methyl[tris(trimethylsilyl)methyl]dichlorostannane

Abstract The compound (Me 3 Si) 3 CSnMeCl 2 reacts with MeOH/MeOK to give the cyclotristannoxane, Me[(Me 3 Si) 3 C]SnO??Sn[C(SiMe 3 ) 3 ](Me)OSnO[CH(SiMe 3 ) 2 ]Me, the structure of which was determined by full X-ray crystallography. Crystals of C 30 H 8 2O 3 Si 8 Sn 3 are monoclinic, a = 13.931(2), b = 18.465(4), c = 21.245(4) A, γ = 104.31(2) 0 , D c = 1.43 g/cm 3 , Z = 4, space group P 2 1 /n. The final R factor is 0.059.

Synthesis, structure and fluxional behaviour of isomeric bis(trimethylstannyl)dihydropentalenes

Abstract Interaction of dihydropentalene (IV) with trimethylstannyldiethylamide in molar ratios of 1:1 or 1:2 leads to mono- or bis-organotin derivatives of IV, respectively. X-ray analysis of trans(E)-bis(trimethylstannyl)dihydropentalene (Va) has been carried out, R = 3.4%. Molecules of Va are centrosyommetric. The parmeters of monoclinic cell: a 8.680(1), b 7.322(1), c 13.073(2) A, β 97.74(1)°, space group P21/c, Z = 2. Geometrical parameters of Va have been determined and their values are discussed in comparison with the same parameters for η1-cyclopentadienyl compounds of elements. Chemical shifts 13C, 1H and 119Sn and coupling constants 13C-119Sn and 117Sn-119Sn of bis- and tris-organotin derivatives of IV have been determined. Rapid intramolecular suprafacial metallotropic rearrangement, proceeding as a [1,5]-sigmatropic shift of SnMe3 group, has been found in Va and cis-(Z)-bis(trimethylstannyl)dihydropentalene (Vb). Activation parameters have been evaluated by the analysis of temperature dependence of 13C NMR spectra within the framework of degenerate two-site exchange in the isomers Va and Vb, EA: 42.2±0.9 and 31.2±0.6 kJ · mole−1; ΔH≠298: 39.8±0.9 and 27.7±0.6 kJ · mole−1; ΔS≠298: −6.2±4.0 and −87.0±3.1 J · mole−1 · K−1 and ΔG≠298: 41.6±1.5 and 54.6±1.1. kJ δ mole−1, respectively.

New stable germylenes, stannylenes, and related compounds 7. Synthesis and structures of compounds Hal—Sn—OCH2CH2NMe2 (Hal = Cl or F)

New stable divalent tin derivatives containing no bulky substituents at the metal atom, Hal—Sn— OCH2CH2NMe2 (Hal = Cl or F), were synthesized, and their crystal structures were studied by X-ray diffraction. Unlike the analogous monomeric divalent germanium derivative Cl—Ge—OCH2CH2NMe2, the new compounds are centrosymmetric dimers formed via two intermolecular Sn←CO coordination bonds.

Heteroorganic betaines: 1. Synthesis of betaines containing the+P−C−Si−S− and+P−C−C−S− fragments and their characterization by multinuclear NMR spectroscopy

A method for the synthesis of a new class of betaines,viz., R31P+CR2R3SiR4R5S−, was developed. The experimental evidence for the intermediate formation of betaines R31P+−CR2R3−CR4R5−S− in the Wittig reaction for a series of thiocarbonyl compounds was obtained. A comparative analysis of the NMR spectra of betaines containing the+P−C−Si−S− and+P−C−C−S− fragments was performed.

Synthesis of the first kinetically stable dibenzosilafulvene

The first stable dibenzosilafulvene, 9-{[8-(dimethylaminomethyl)-1-naphthyl]phenylsil-1-ylium}fluoren-9-ide (7a), was obtained in one step from 9-fluorenyllithium and chloro[8-(dimethylaminomethyl)-1-naphthyl]phenylsilane as a stable solvate with THF. The structure of the zwitterionic compound7a was established by1H,13C, and29Si NMR in solution and in the solid state. The reactions of compound7a with crotonaldehyde, ethanol, and triethylethylidenephosphorane are described. The data on the synthesis of alkoxy- and alkylthiochloro-9-fluorenylsilanes and their phosphonium salts are given.

New Stable Germylenes, Stannylenes, and Related Compounds II. Bis(butylthio)tin(II) and ate-Complexes [(Me3Si)3CE(μ-SBu)2Li(THF)2] (E = Ge,Sn). Synthesis and Structure

By reaction of Me3SiSBu with anhydrous tin(II) chloride bis(butylthio)tin was obtained that exemplified a coordination polymer [Sn(SBu)2]n, whose elementary unit contained according to X-ray diffraction study three independent four-membered rings Sn2S2 of unusual geometry. It was demonstrated that polymeric thiolates [E(SBu)2]n (E = Ge, Sn) readily reacted with TsiLi (Tsi = C(SiMe3)3) in a mixed solvent ether THF affording in a good yield ate-complexes [(Me3Si)3CE(μ-SBu)2Li(THF)2]. Both complexes contain a four-membered ring in a butterfly conformation where the lithium atom is symmetrically bonded to both sulfur atoms, and the coordination polyhedra of Ge and Sn atoms may be regarded as distorted tetrahedra AB3X, where one of coordination places is occupied by unshared electron pair. The structure of the ate-complexes observed in a crystal is conserved also in solution of nonpolar solvents.

New heteroorganic betaines containing the (+)E15—C—E14—X(–) and (+)E15—C—E14(–) structural fragments (E15 = P, As; E14 = Si, Ge, Sn; X = C, S, O, NR)

The review surveys the data on the reactions of phosphorus and arsenic ylides with compounds containing E=X bonds (E = C, Si, Ge, or Sn; X = C or S), cyclic oligomers (R2ES)n (n = 2 or 3), and heavier analogs of carbenes. These reactions give rise to two new classes of heteroorganic betaines containing the (+)E15—C—E14—X(–) (I) and (+)E15—C—E14(–) (II) (E15 = P or As; E14 = Si, Ge, or Sn; X = C or S) structural fragments. Procedures for the synthesis of these compounds, their reactivities, the X-ray diffraction structures, and the electronic structures established by high-level quantum-chemical calculations are considered in detail. The carbon analogs of betaines of type I, viz., compounds bearing the (+)P—C—C—X(–) fragment (III), are also discussed. The latter were long considered as possible intermediates in the reactions of compounds containing the polar C=X bond (X = C, O, S, NR, etc.) with phosphorus ylides (classical Wittig and Corey—Chaykovsky reactions and related processes).

X-ray diffraction study of the first monomeric dioxygermylene Ge(OCH2CH2NMe2)2 stabilized by two Ge ← N intramolecular coordination bonds: The influence of Ge ← N intramolecular coordination bonds on the structure and packing of molecules in crystals

The molecular and crystal structures of the first monomeric dioxygermylene Ge(OCH2CH2NMe2)2 (I) stabilized by two Ge ← N intramolecular coordination bonds are determined by X-ray diffraction analysis. The Ge ← N bond lengths in two independent molecules are equal to 2.329(2), 2.337(2) and 2.324(2), 2.346(2) Å, respectively. The central germanium atom plays the role of a spiro atom between two five-membered heterocycles in the envelope conformation and adopts a trigonal-bipyramidal configuration with a lone electron pair in the equatorial position. Compound I has two planar-chiral isomers which crystallize jointly. Molecules in the crystal have a layered packing (molecular layers are perpendicular to the [001] direction) composed of four translationally independent equivalent layers. These layers are spaced at 1/4c intervals and displaced with respect to each other by approximately +0.35a, −1/4b, −0.35a, and +1/4b, respectively. The characteristic displacement of the layers and their proper symmetry (pba2) that differs from the symmetry of the crystal (space group P212121) determine a large variety of pseudosymmetry operations.