An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Hydrolysis of monochelate five-coordinate chlorosilanes MeC(O)N(Me)CH2SiMe2Cl (Ia), L7CH2SiMe2Cl (Ib), L8CH2SiMe2Cl (Ic), PhtImCH2SiMe2Cl (Id), MeC(O)N(Me)CH2SiMePhCl (IIa), and Im5CH2SiMePhCl (IIe), containing a monoanionic C,O-chelating ligand LCH2 [L is an amide, n-membered lactam (L n ), imide (Im n ), or phthalimide (PhtIm) residue]. The structures of the starting chlorides and their hydrolysis products were established by means of X-ray diffraction analysis. Based on experimental and published data, a general scheme of hydrolysis of mono-C,O-chelate chlorosilanes was suggested, including initial formation of silyloxonium chlorides III and subsequent formation of disiloxane dihydrochlorides IV.

Cationic O→Si-coordinated bis-C,O-chelate silicon complexes [(LCH2)2Si(F)]BF4, containing monoanionic AcN(Me)CH2, 2-oxoperhydroazepinomethyl, 2,2-dimethyl-4-oxobenzo[1,3]oxazin-3-ylmethyl, and 4-methyl-2-oxoquinolinomethyl C,O-coordinating ligands were synthesized by the reaction of trimethylsilyl derivatives of amides, lactams, and related compounds with (ClCH2)2SiCl2 in a 2:1 ratio. The synthesized complexes were reacted with KF to obtain six-coordinate bis-C,O-chelates [(LCH2)2SiF2] which were then converted into the starting tetrafluoroborates by treatment with BF3·Et2O. First representatives of cationic bis-O,O′-chelate silicon complexes with a 2-hydroxyacid amide fragment {XSi[OCH(R)C(O)NMe2]2}Y (X = Cl, Me, t-Bu, Ph, BrCH2; R = H, Me; Y - Cl−, ClHCl−, HgBr 3 − ) were synthesized by the reaction of XSiCl3 with O→SiMe3 derivatives of dimethylamides of (S)-lactic and glycolic acids in a 1:2 ratio or by transesterification of XSi(OMe)3 with glycolic acid dimethylamide followed by addition of acetyl bromide (ratio 1:3:1). The structure of the resulting chelates was proved by X-ray diffraction analysis.

Reactions of GeBr 4 with N,N -dimethyl-2-trimethylsiloxypropionamide ( 2a ), ( S )-2-trime-thylsiloxypropionpyrrolidide (( S )- 2b ), and N,N -dimethyl- O -(trimethylsilyl)mandelamide ( 2c ) afforded pentacoordinated neutral (O,O)-monochelates, viz. , N,N -dimethyl-2-tribromoger-myloxypropionamide ( 3a ), ( S )-2-tribromogermyloxypropionpyrrolidide (( S )- 3b ), and N,N -dimethyl- O -(tribromogermyl)mandelamide ( 3c ), respectively. X-ray diffraction study was performed for tribromides 3a , ( S )- 3b , and 3c , as well as for the N,N -dimethylmandelamide ( 1c ) described earlier. According to the X-ray diffraction data, the Ge atom in tribromides 3a , ( S )- 3b , and 3c is pentacoordinated and has trigonal bipyramidal configuration with two halogen atoms and oxygen atom of the ether group in the equatorial positions and the halogen atom and the amide oxygen atom in the axial fragment, the bonds in which are somewhat longer as compared to the analogous bonds in tetracoordinated Ge compounds.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

New mono-and bis-chelate hypercoordinate silicon complexes containing the monoanionic C,O-chelating 2,2-dimethyl-2,3-dihydrobenzo-1,3-oxazin-3-ylmethyl (BonCH2) ligand were synthesized starting from 2,2-dimethyl-2,3-dihydrobenzo-1,3-oxazin-4-one (1) through its TMS derivative 2. The reactions of compound 2 with the chlorosilylmethylating agents ClCH2SiMe2Cl, ClCH2SiMeCl2, and (ClCH2)2SiCl2 followed by the transformations of the initially formed chlorosilanes BonCH2SiMe2Cl (3), BonCH2SiMeCl2 (6), and [(BonCH2)2Si(Cl)]+Cl− (8), respectively, into the target products afforded neutral monochelates, viz., monofluoride BonCH2SiMe2F (5) and difluoride BonCH2SiMeF2 (7), and the bis-chelate disiloxane cation-anion complexes {[(BonCH2)2Si]2O}2+·Cl−·ClHCl− (9) and {[(BonCH2)2Si]2O}2+·2TfO− (10). The reaction of ditriflate 10 with boron trifluoride etherate produced fluoride triflate (BonCH2)2Si(F)OTf (11). The X-ray diffraction study of compounds 5, 7, 9, 10, and 11, as well as of NH-heterocycle 1 and disiloxane (BonCH2SiMe2)2O (4) studied earlier, demonstrated that the Si atoms in complexes 5, 7, 9, and 10 are pentacoordinate through the formation of an intramolecular O→Si bond. The coordination of silicon in fluoride triflate 11 can be described as 5+1. In disiloxane 4, one of two Si atoms is pentacoordinate. Dinuclear cation-anion complexes 9 and 10 contain the diastereomeric bis-silylium ions {[(BonCH2)2Si]2O}2+, which differ in the configuration of the chiral bis-chelate fragments (BonCH2)2Si. In complex 9, these fragments have opposite configurations (ΛΔ); in ditriflate 10, the same configurations (ΛΛ).

Hydrolysis is one of the most common reactions for halides of both tetraand pentacoordinate silicon. In the compounds with an intramolecular coordination, the process might be complicated by the involvement of the coordinating donor atom. We have studied the hydrolysis of pentacoordinate chlorosilanes LCH2Si(R)MeCl (1, R = Me, Ph) with the intramolecular coordination O→Si in mono(C,O)-chelate bidentate monoanionic amidomethyl [LCH2 = R’C(O)NR”CH2; R’ = Alk, Ph; R” = H, Me, CH(Me)Ph], lactamomethyl or imidomethyl (LCH2 or ImCH2, respectively; n = ring size) ligands.

N-(Dimethylfluorosilylmethyl)succinimide (2a) and N-(dimethylfluorosilylmethyl)phthalimide (2b) were synthesized by the Si—N bond cleavage in readily accessible N-(dimethylimidosilylmethyl)imides with BF3 etherate. Analogously, (O→Si)-chelated 1-(dimethylfluorosilylmethyl)-2-pyrrolidone was prepared from 1-(dimethylmorpholinosilylmethyl)-2-pyrrolidone. X-ray diffraction study demonstrated that the silicon atom in the crystals of 2b is pentacoordinated.

A general scheme of reactions between chloro(chloromethyl)dimethylstannane and N-trimethylsilylamides and -lactams was established by NMR and IR techniques. The reactions proceed via transmetallation followed by transformation of the N-stannylated intermediate (1) into (N-Sn)-coordinated O-stannylmethyl (2) and (O-Sn) -coordinated N-stannylmethyl (3) derivatives. In the cases of 2-piperidone and 2-hexahydroazepinone these products were isolated as individual compounds (2b,c and 3b,c). X-ray diffraction study of 1-(chlorodimethylstannylmethyl)-2-piperidone (3b) confirmed (3 + 2)-coordination state of the tin atom and axial positions of oxygen and halogen atoms. The experimental and quantum-chemically calculated structural parameters are discussed in comparison with those of related trigonal bipyramidal (TBP) silicon, germanium and tin derivatives. Calculation at the MP2/LanL2DZ/D95 level reveals that the stability of the (O-M)chelates increases in the following order: (O-Si) < (O-Ge) < (O-Sn). (c) 2005 Elsevier B.V. All rights reserved.

A method has been developed for the synthesis of a bis(O→Si)-chelated bis(2,2-dimethylbenzo[2H]-4-oxo-1,3-oxazino-3-methyl)difluorosilane from 2,2-dimethyl-3-trimethylsilylbenzo[2H]-1,3-oxazin-4-one and bis(chloromethyl)dichlorosilane via the intermediate formation of the corresponding unstable bis-chelated dichloride, subsequent hydrolysis with NaHCO3 and, without separation, treatment of the hydrolysis product with boron trifluoride etherate. Analysis of the electron density distribution showed the presence of dative bonding in both O→Si-F fragments.

The reaction of 4-(2-hydroxybenzoyl)-2,2,6,6-tetramethyl-2,6-disilamorpholine with BF3⋅Et2O afforded (O-B)-chelate 4-[2-(difluoroboroxy)benzoyl]-2,2,6,6-tetramethyl-2,6-disilamorpholine. Treatment of the latter with BF3⋅Et2O or SOCl2 gave rise to products of the disilamorpholine ring opening, viz., (O-B) chelate 2-(difluoroboroxy)-N,N-bis(dimethylfluorosilylmethyl)benzamide or 2-(difluoroboroxy)-N, N-bis(dimethylchlorosilylmethyl)benzamide, respectively. The structures of the compounds synthesized were confirmed by X-ray diffraction analysis and 1H, 13C, and 29Si NMR spectroscopy. High-precision X-ray diffraction study and quantum-chemical calculations demonstrated that the coordination O→Si bond is absent in the two last-mentioned compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The synthesis of N -(chlorodimethylsilylmethyl)succinimide and N -(chlorodimethylsilylmethyl)-glutarimide by the reaction of the corresponding N -trimethylsilylimides with chlorodimethylsilane and by the reaction of unsubstituted imides with a mixture of hexamethyldisilazane with dimethylchloromethylchlorosilane is described. The formation of N -(chlorodimethylsilylmethyl)succinimide is followed by substitution by the silicon atom, which, depending on the reagent ratio, provides N -(dimethylsuccinimidomethyl)succinimide as the major or minor product. 1 H, 13 C, and 29 Si NMR spectroscopy and X-ray diffraction analysis showed that the silicon atom in N -(chlorodimethylsilylmethyl)glutarimide is five-coordinate. By contrast, in N -(chlorodimethylsilylmethyl)succinimide and N -(dimethylsuccinimidomethyl)succinimide, according to NMR and X-ray diffraction data, the silicon atom is four-coordinate. Quantumchemical calculations by the AM1 method show that the molecular conformations of N -(chlorodimethylsilylmethyl)imides containing an intramolecular O→Si bond are not energetically most favorable in the gas phase.

The reaction of dichloride (L5)2GeCl2 with LiI·H2O under conditions, which did not exclude exposure to atmospheric oxygen, as well as hydrolysis of chloride triflate (L7)2Ge(Cl)OTf in the presence of Et3N and of perchlorate (L5)2Ge(Cl)OClO3 by atmospheric moisture afforded cation-anionic complexes containing the digermoxane dications of the general formula [(L n )2GeOGe(L n )2]2+ (L n is a lactamomethyl n-membered bidentate C,O-coordinating ligand) with the triiodide, triflate, and perchlorate ions, respectively. According to the results of X-ray diffraction study, the digermoxane dications in these complexes contain two pentacoordinate Ge atoms each and occur as germylium ions stabilized by two O→Ge coordination bonds. In these complexes, the digermoxane dications are diastereomers in which the bischelate systems have opposite configurations.