Octahedral HSiCl3 and HSiCl2Me Adducts with Pyridines

Si⋯O proximity in imidosilanes – absence of orbital interactions

New N-silylated phthalimides, succinimides, and 1,8-napthalimides were synthesised by reactions of the alkali imides with chlorosilanes in THF. Six different mono-, di-, tri- and tetra-iminosilanes of the type (CH3)4–n Si(imide) n were obtained and the products analysed with 1H, 13C, 29Si NMR, and Raman spectroscopy. The molecular structures of four imidosilanes have been determined by single-crystal X-ray diffraction. A characteristic structural feature of the compounds is the fact that all intramolecular Si⋯O distances are significantly below the sum of the van-der-Waals radii of silicon and oxygen of 3.62 Å. Experimentally found values for Si⋯O distances range from 2.813 to 3.030 Å. However, there are no significant orbital interactions between silicon and oxygen atoms, as shown by quantum chemical analysis with AIM and NBO methods. The short Si⋯O distances in these molecules are caused by the geometry of the rigid imide group bound to the silicon atom, and there is no evidence for an increase of the coordination number of the Si atoms.

Hydrosilylation in Aryliminopyrrolide-Substituted Silanes

A range of silanes was synthesized by the reaction of HSiCl3 with iminopyrrole derivatives in the presence of NEt3 . In certain cases, intramolecular hydrosilylation converts the imine ligand into an amino substituent. This reaction is inhibited by factors such as electron-donating substitution on Si and steric bulk. The monosubstituted ((Dipp) IMP)SiHMeCl ((Dipp) IMP=2-[N-(2,6-diisopropylphenyl)iminomethyl]pyrrolide), is stable towards hydrosilylation, but slow hydrosilylation is observed for ((Dipp) IMP)SiHCl2 . Reaction of two equivalents of (Dipp) IMPH with HSiCl3 results in the hydrosilylation product ((Dipp) AMP)((Dipp) IMP)SiCl ((Dipp) AMP=2-[N-(2,6-diisopropylphenyl)aminomethylene]pyrrolide), but the trisubsitituted ((Dipp) IMP)3 SiH is stable. Monitoring the hydrosilylation reaction of ((Dipp) IMP)SiHCl2 reveals a reactive pathway involving ligand redistribution reactions to form the disubstituted ((Dipp) AMP)((Dipp) IMP)SiCl as an intermediate. The reaction is strongly accelerated in the presence of chloride anions.

Poly(vinylpyrrolidone) stabilized aluminum nanoparticles obtained by the reaction of SiCl4 with LiAlH4

Isolation and stabilization of Al nanoparticles has been possible by the reaction between SiCl₄ and LiAlH₄ in the presence of poly(vinylpyrrolidone).

Pentacoordinate silicon(IV): cationic, anionic and neutral complexes derived from the reaction of NHC→SiCl4 with highly Lewis acidic (C2F5)2SiH2

Addition of NHC→SiCl4 to the highly Lewis acidic bis(pentafluoroethyl)silane ((C2F5)2SiH2) afforded the salt [(NHC)2SiCl2H][(C2F5)2SiCl3] with pentacoordinate silicon in the cation and the anion. The anion represents the first example of a chlorosilicate structurally characterized in the solid state. In this reaction, the long sought pentacoordinate NHC-adduct of silicochloroform was identified as an intermediate and its crystal structure is presented.

Neutral six-coordinate and cationic five-coordinate silicon(IV) complexes with two bidentate monoanionic N,S-pyridine-2-thiolato(-) ligands

A series of neutral six-coordinate silicon(IV) complexes (4-11) with two bidentate monoanionic N,S-pyridine-2-thiolato ligands and two monodentate ligands R(1) and R(2) was synthesized (4, R(1) = R(2) = Cl; 5, R(1) = Ph, R(2) = Cl; 6, R(1) = Ph, R(2) = F; 7, R(1) = Ph, R(2) = Br; 8, R(1) = Ph, R(2) = N3; 9, R(1) = Ph, R(2) = NCO; 10, R(1) = Ph, R(2) = NCS; 11, R(1) = Me, R(2) = Cl). In addition, the related ionic compound 12 was synthesized, which contains a cationic five-coordinate silicon(IV) complex with two bidentate monoanionic N,S-pyridine-2-thiolato ligands and one phenyl group (counterion: I(-)). Compounds 4-12 were characterized by elemental analyses, NMR spectroscopic studies in the solid state and in solution, and crystal structure analyses (except 7). These structural investigations were performed with a special emphasis on the sophisticated stereochemistry of these compounds. These experimental investigations were complemented by computational studies, including bonding analyses based on relativistic density functional theory.

Ylenes in the M(II)→Si(IV) (M=Si, Ge, Sn) coordination mode

The reaction of the methimazolyl (mt, i.e., 2-mercapto-1-methylimidazolide) substituted silane Si(mt)(4) with SnCl(2) and GeCl(2) in dioxane affords the paddlewheel-shaped complexes [ClSi(μ-mt)(4)MCl] (M=Sn (1) and Ge (2), respectively). These compounds represent the first crystallographically characterized hexacoordinate silicon complexes comprising a Sn or Ge atom in the Si coordination sphere. An attempt to synthesize the related silicon compound 3 [ClSi(μ-mt)(4)SiCl] instead afforded the trisilane [ClSi(μ-mt)(4)Si-SiCl(3)] (3a), which provides the first crystallographic evidence for the feasibility of oligosilanes with adjacent hexacoordinate Si atoms. One of the hexacoordinate Si atoms of 3a features the unprecedented (Si(2)S(4))Si skeleton. Natural bonding orbital (NBO) analyses of compounds 1, 2, 3a (and the target compound 3) revealed characteristics of M(II)→Si(IV) (for 2 and 3) or M(I)→Si(IV) (for 3a) dative bonding in the systems with M=Si and Ge, whereas compound 1 exhibits a covalent Sn(III)-Si(III) bond.

Highly efficient diastereoselective reduction of alpha-fluoroimines

A highly selective reduction of alpha-fluoroimines to the corresponding beta-fluoroamines has been developed utilizing trichlorosilane as the reductant. The key aspect of this reaction is the ability of fluorine and nitrogen to activate organosilanes leading to high diastereoselectivity (>100:1) in the product distribution. This new method provides a new avenue for the diastereoselective synthesis of beta-fluorinated amines in good yields and selectivity.