A correction to the molecular structure of [dimethyl(phenyl)silyl]tris(trimethylsilyl)methane

In a recently published structure of (Me₃Si)₃C(SiMe₂Ph) the hydrogen atoms were inadvertently misplaced. The hydrogen atom positions have been redetermined and the structure refinement repeated. There is no significant change in the averaged values for chemically equivalent bond lengths and angles from those previously reported, and the previous conclusions stand.     

Bimolecular displacements of iodine in reactions of dimethyl[tris(trimethylsilyl)methyl]silyl iodide with salts

Direct nucleophilic displacement of iodine to give (Me₃Si)₃ CSiMe₂ Y, where Y = F, NCO, NCS, CN or N₃, takes place when (Me₃Si)₃ CSiMe₂I is treated with solutions of CsF, KOCN, KSCN, KCN, or NaN₃ in MeOH or CH₃ CN. The order of effectiveness of the nucleophiles appears to be N₃ > F > CN > NCS > NCO in MeOH and NCS > NCO > CN, F in CH₃ CN.     

Remarkable tris(trimethylsilyl)silyl group for diastereoselective [2 + 2] cyclizations

[reaction: see text] Diastereoselective [2 + 2] cyclizations of aldehyde- and ketone-derived silyl enol ethers with acrylates is described. The use of the tris(trimethylsilyl)silyl group allows for unprecedented reactivity, yields, and selectivity for these cyclizations. The presence of silicon-silicon bonds proved to be important for this transformation, where typical silyl groups (TBS and TIPS) failed to give any desired product. The bulky bis(2,6-diphenylphenoxide) aluminum triflimide catalyst was essential for high diastereoselectivity.     

Bis[tris(trimethylsilyl)silyl]zink, -cadmium und -quecksilber,schwingungsspektroskopische Daten und Strukturanalysen

Bis[tris(trimethylsilyl)silyl] Zinc, Cadmium, and Mercury – a Structural Study by IR and Raman Spectroscopy and X-Ray Analyses Raman and FT-IR spectra of bis[tris(trimethylsilyl)silyl] zinc ( 1 ), cadmium ( 2 ) and mercury ( 3 ) were recorded. The vibrational data are in agreement with either D_3h or a D_3d symmetry. The latter had been shown to be the correct one at least for the solid state by X-ray diffraction experiments. All three compounds crystallize isomorphically in the triclinic centrosymmetric space group P1 . [ 2 (T = 293 K): a = 9.4388(11); b = 9.744(2); c = 12.926(2); α = 68.200(12); β = 71.971(10); γ = 60.925(10); Z = 1; (T = 173 K): a = 9.336(6); b = 9.585(5); c = 12.488(8); α = 68.77(4); β = 72.28(4); γ = 62.06(4); 3 : a = 9.467(2); b = 9.749(2); c = 12.885(2); α = 67.840(14); β = 71.510(14); γ = 60.890(14); Z = 1]. The Hg—Si bondlength in 3 was found to be 246.9(2)pm, somewhat shorter then in all disilylmercury derivatives investigated sofar and even shorter than the Cd—Si bond in 2 (250.4(1)pm). Bondlengths and angles within the tris(trimethylsilyl)silyl group are virtually equal in all three group 12 derivatives and lie in the expected range.     

The crystal and molecular structure of tris[(triphenylstannyl)methyl]methane

The title compound, C₅₈H₅₂Sn₃, belongs to the triclinic space group P$\text{1}$, with a 10.165, b 13.365, c 18.670 Å, α 96.28, β 93.88, γ 103.15°, V = 2443.8 ų, f_w = 1105.1, Z = 2, D_calc 1.501 g cm^?3, m.p. 206.5–208°C, λ(Mo-K_$\text{α}$) 0.71069 Å. The structure was refined on 2684 nonzero reflections to an R factor of 0.044. The crystal contains molecules in which the (SnCH₂)₃CH core possesses an approximate C₃ symmetry. The three SnC(H₂) bonds are gauche to the C(4)-H bond. Repulsive interactions involving the bulky Ph₃Sn substituents lead to large SnC(H₂)C(H) angles (av. 117.3°), whereas the C(H₂)C(H)C(H₂) angles at the tertiary carbon average 111.3°. Little distortion of the Ph₃Sn groups themselves is present, since the PhSnPh angles (av. 109.8°) are almost equal to the C(H₂)SnPh angles (av. 109.9°). The molecule as a whole has no symmetry because the aromatic rings in the three Ph₃Sn groups have different orientations. The phenyl groups create a pocket in the middle of the molecule which encloses and shields the tertiary hydrogen atom. The resulting inaccessibility of this hydrogen accounts in part for the low reactivity of the title compound in redox reactions.     

Tris(trimethylsilyl)silylamin und seine lithiierten und silylierten Derivate — Kristallstruktur des dimeren Lithium-trimethylsilyl-[tris(trimethylsilyl)silyl]amids

Tris(trimethylsilyl)silylamine and the lithiated and silylated Derivatives — X-Ray Structure of the dimeric Lithium Trimethylsilyl-[tris(trimethylsilyl)silyl]amide The ammonolysis of the chlor, brom or trifluormethanesulfonyl tris(trimethylsilyl)silane yields the colorless tris(trimethylsilyl)silylamine, destillable at 51°C and 0.02 Torr. The subsequent lithiation, reaction with chlor trimethylsilane and repeated lithiation lead to the formation of lithium tris(trimethylsilyl)silylamide, trimethylsilyl-[tris(trimethylsilyl)silyl]amine and finally lithium trimethylsilyl-[tris(trimethylsilyl)silyl]amide, which crystallizes in the monoclinic space group P2₁/n with a = 1 386.7(2); b = 2 040.2(3); c = 1 609.6(2) pm; β = 96.95(1)° and Z = 4 dimeric molecules. The cyclic Li₂N₂ moiety with Li? N bond distances displays a short transannular Li …? Li contact of 229 pm. The dimeric molecule shows nearly C₂-symmetry, so that one lithium atom forms agostic bonds to both the trimethylsilyl groups, the other one to the tris(trimethylsilyl)silyl substituents. However, the ⁷Li{¹H}-NMR spectrum displays a high field shifted singlet at —1.71 ppm. The lithiation of trimethylsilyl-[tris(trimethylsilyl)silyl]amine leads to a high field shift of the ²⁹Si{¹H} resonance of about 12 ppm for the Me₃SiN group, whereas the parameters of the tris(trimethylsilyl)silyl ligand remain nearly unaffected.     

Tris(trimethylsilyl)silyl versus tris(trimethylsilyl)germyl: Radical reactivity and oxidation ability

A comparison of the tris(trimethylsilyl)silyl I and tris(trimethylsilyl)germyl II radical reactivity is provided. Their formation as well as their reactivity encountered in a large variety of chemical processes (addition to double bond, halogen abstraction, peroxyl radical formation…) is examined by laser flash photolysis, quantum mechanical calculations and electron spin resonance (ESR) experiments. The starting compound (TMS)₃GeH is more reactive than (TMS)₃SiH toward the t-butoxyl, the t-butylperoxyl and the phosphinoyl radicals. A similar behavior is noted for an aromatic ketone triplet state. II exhibits a lower absolute electronegativity: accordingly, the addition to electron rich alkenes is less efficient than for I. Radical II is also found less reactive for both the peroxylation and the halogen abstraction reactions. The rearrangement of is slower than for ; this is related to the respective exothermicity of the processes.     

Phosphino[tris(trimethylsilyl)methyl]Boranes and 2,4‐Bis[tris(trimethylsilyl)methyl]‐1,3,2,4‐diphosphadiboretanes [1]

The reaction of tris(trimethylsilyl)methylboron dihalides (Me₃Si)₃CBX₂ (X = Cl, F) with the lithium phosphides LiPHtBu and LiPHmes leads to the phosphinoboranes (Me₃Si)₃CBX‐(PHR), (Me₃Si)₃CB(PHR)₂ or the 1,3,2,4‐diphosphadiboretanes [(Me₃Si)₃CB(PR)]₂, depending on the ratio of the reagents, the reaction temperature and concentration. High dilution and low temperatures are required for the synthesis of (Me₃Si)₃CB(Hal)PHR ( 1–3 ) in order to prevent the formation of (Me₃Si)₃CB(PHR)₂ ( 4 and 5 ). The latter compounds are best prepared in a two step phosphination from (Me₃Si)₃CBHal₂ and LiPHR. At higher temperatures the four‐membered 1,3,2,4‐diphosphadiboretanes [(Me₃Si)₃CB(PR)]₂ 6 and 7 are the most stable compounds. On the other hand, compounds of type (Me₃Si)₃CB(Hal)PR₂, 8 and 9 , are thermally more stable than the monophosphinoboranes 1 – 3 . Phosphinoboranes of type (Me₃Si)₃CB(PR₂)₂ (R = tBu, mes) could not be prepared. NMR and mass spectral data are in accord with the monomeric nature of compounds 1 to 9 .     

Synthesis and reactions of [tris(trimethylsilyl)methyl]ethyl dichlorosilane

The crowded dichlorosilane TsiSiEtCl₂, (1), (Tsi = (Me₃Si)₃C) was prepared from the reaction between EtSiCl₃ and TsiLi, then it was reduced with LiAlH₄ to give TsiSiEtH₂, (2). The hydride (2) was then treated with two equivalents of ICl/CCl₄ or Br₂/CCl₄ to produce TsiSiEtI₂, (3), and TsiSiEtBr₂, (4), respectively. The reaction of compound (2) with one equivalent of ICl/CCl₄ gives TsiSiEtHI, (5). This product reacted with H₂O/dioxane in the presence of AgClO₄ or with dry MeOH to produce TsiSiEtHOH, (6), and TsiSiEtHOMe, (7), respectively. The compound (3) reacted with H₂O in DMSO/CH₃CN to give TsiSiEt(OH)₂, (8), and the compound TsiSiEtIOMe, (9), was prepared from the reaction of the compound (7) with ICl/CCl₄. When the dichloride (1) was treated with NaOMe/MeOH it gave (Me₃Si)₂CHSiEt(OMe)₂. It is suggested that the reaction proceeds through an elimination-addition mechanism. The dichloride (1) was also treated with KSCN, NaN₃ or NaOCN in CH₃CN to give S_N2 substitution products. All the new products were characterized by FTIR, ¹H NMR, and ¹³C NMR spectroscopy, mass spectrometry and elemental analysis.     

Cycloadditionsreaktionen von Isocyaniden an Bis[tris(trimethylsilyl)methyl]diphosphen

Cycloaddition Reactions of Isocyanides with Bis[tris(trimethylsilyl)methyl]diphosphene The [2 + 1] cycloaddition reactions of isocyanoacetonitrile ( 1 a ), pentacarbonyl(diisocyanomethane)chromium ( 1 b ), and 2,2,2-trifluoroethylisocyanide ( 1 c ) with the diphosphene R–P=P–R (R = C[Si(CH₃)₃]) ( 2 ) yield the expected diphosphirane imines 3 a – c . All compounds are thermally very stable and show no evidence for a [2 + 1] cycloreversion reaction. The structures of 3 a : triclinic, P 1, a = 918.0(2), b = 1174.7(4), c = 1821.9(5) pm, α = 93.83(2), β = 97.22(2)°, γ = 97.08(2)°, Z = 2, R₁ = 0.069; 3 c : monoclinic, P2₁, a = 928.6(2), b = 1659.8(3), c = 1261.2(3) pm, β = 107.65(2)°, Z = 2, R₁ = 0.073, and 1,2-Bis[tris(trimethylsilyl)]methyl-N-trifluormethyl-3-diphosphiranimin: monoclinic, P2₁/n, a = 1374.6(3), b = 1685.9(1), c = 1658.6(5) pm, β = 108.99(9)°, Z = 4, R₁ = 0.092, were elucidated by X-ray crystallography. All three compounds possess a similar three membered PCP ring system with an exocyclic C–N double bond.     

The mass spectra of some tris(trimethylsilyl)acylsilanes and tris(trimethylsilyl)silanes

While tris(trimethylsilyl) alkanoylsilanes fragment in the acylsilane form yielding [(Me₃Si)₃SiCO]⁺ by α-cleavage, the molecular ions of their aryl counterparts rearrange to ionized silaethenes prior to cleavage, paralleling known photochemical behaviour. Sila-allyl type structures are attributed to the stable [M? Me˙]⁺ ions obtained by subsequent cleavage. Metastable ion characteristics reveal the identity of the structures of the monomeric silaethene ions obtained from one of the aroylsilanes and a 1,2-disilacyclobutane. The non-compliance of the alkanoylsilanes with their photochemical behaviour is attributed to a preferred elimination of the stable alkyl radical (R˙) from the molecular ions. Several polysilanes display abundant odd-electron ions which may possess a disilene structure.     

Polysilane derivatives of the transition metals II. The crystal and molecular structure of [tris(trimethylsilyl)silyl]pentacarbonylmanganese, (Me3Si)3SiMn(CO)5

The crystal and molecular structures of [tris(trimethylsilyl)silyl]pentacarbonylmanganese, (Me₃Si)₃SiMn(CO)₅, have been determined from three-dimensional X-ray data obtained by counter methods. The compound crystallizes in space group P$\text{1}$ of the triclinic system, with two molecules in a unit cell of dimensions: a = 9.002(2), b = 9.655(2), c = 15.639(3) Å, α = 83.66(1), β = 105.65(1), γ = 114.61(1)°.The observed and calculated densities are 1.20 (±0.03) and 1.23 g-cm^?3 respectively. Full-matrix least-squares refinement of the structure has led to a final value of the conventional R factor of 0.059 for the 818 independent reflections having F² > 3σ(F²).The coordination geometry about the manganese atom is approximately octahedral and, about the silicon atom bonded to the manganese atom, tetrahedral.The relative orientations of carbonyl and trimethylsilyl groups, when viewed down the MnSi bond, appear consistent with minimization of energy due to nonbonded interactions.Two of the equatorial carbonyl groups are displaced out of the equatorial plane towards the silicon ligand by 6°. The SiMn bond is 2.564(6) Å long and has no multiple character.     

Bis[4‐(salicylideneamino)phenyl]methane

The crystal structure of the title Schiff base {systematic name: 2,2′‐[methyl­ene­di‐p‐phenyl­ene­bis(nitrilo­methyl­idyne)]­diphenol}, C₂₇H₂₂N₂O₂, consists of intra­molecularly hydro­gen‐bonded mol­ecules inter­linked by C—H⋯O hydrogen bonds [C⋯O = 3.426 (2) Å and C—H⋯O = 152.7 (17)°]. The mol­ecule is in the enol form and is located on a twofold axis. The central methane C atom of the diphenyl­methane motif is displaced from the aromatic ring planes. This effect is compared with previous results, which display an inverse correlation between the out‐of‐plane displacement and the C—C—C angle around the central methane C atom. In the title compound, the displacement is 0.124 (2) Å and the C—C—C angle is 110.18 (19)°.     

Improvements in the preparation and use of [tris(trimethylsilyl)methyl]lithium

Improvements in the preparation and use of [tris(trimethylsilyl)methyl]lithium are described.     

Un Nouveau diphosphene stable: Le bis[tris(trimethylsilyl)methyl] diphosphene

A new stable diphosphene (Me₃Si)₃CPPC(SiMe₃)₃ has been isolated and characterized particularly by its NMR data; the ³¹P NMR chemical shift appears to be the largest ever observed.