The reaction of N -trimethylsilyl derivatives of amides and imides with alkyl sulfonates on heating affords the corresponding N -alkyl derivatives and trimethylsilyl sulfonates.

Derivatives of the amino acids sarcosine and proline – triflates TsN(Me)CH2C(O)N(Me)-CH2SiMe2OTf and Ns–Pro–N(Me)CH2SiMe2OTf (Ns is 4-NO2C6H4SO2) – were synthesized by the reaction of trimethylsilyl triflate with halosilanes prepared previously. Bromide NsNHCH(Me)C(O)N(Me)CH2SiMe2Br was synthesized by the cleavage of the Si–O–Si moiety of the appropriate disiloxane with excess acetyl bromide. The X-ray diffraction study of these compounds and of the previously characterized bromide TsN(Ac)CH2C(O)N(Me) CH2SiMe2Br showed that the Si–O coordination bond lengths in the triflates are 1.7692(14)– 1.8623(14) Å. The interatomic distances between the bromine and silicon atoms are 2.7095(8) and 2.9704(7) Å, which indicates that these bonds are weak. To elucidate the nature of Si…X bonding (X = OTf, Br), the topological analysis of electron density was performed and 29Si NMR chemical shifts were calculated. The interatomic Si…X interaction in triflate TsN(Me)CH2C(O)- N(Me)CH2SiMe2OTf and bromide TsN(Ac)CH2C(O)N(Me)CH2SiMe2Br is weak. In triflate Ns–Pro–N(Me)CH2SiMe2OTf and bromide NsNHCH(Me)C(O)N(Me) CH2 SiMe2Br, the Si…X interaction is significantly stronger and corresponds to a weak coordination bond. Hence, the tosylates can be considered as salts, whereas the para-nitrobenzenesulfonyl derivatives are monochelated five-coordinate silicon complexes.

Anionic five-coordinate complexes with two bis-O,O’-chelating ligands bearing α-hydroxy acid moieties, dicyclohexylammonium salts $$\text{Cy}_{2}\text{NH}_{2}{^+}\{\text{PpnCH}_2\text{Si}[\text{OCR}_2\text{C}\text{(O)O]}_2\}^-$$ (Cy is cyclohexyl, PpnCH2 is 4-methyl-2,5-dioxopiperazin-1-ylmethyl, R = Me, Ph), were synthesized by esterification of alkoxysilane PpnCH2Si(OMe)3 with α-hydroxy acids (dimethyl- and diphenylgylcolic acids) in the presence of dicyclohexylamine. The five-coordinated state of the silicon atom in the resulting compounds in solution was confirmed by 29Si NMR spectroscopy. According to the X-ray diffraction data, the synthesized compounds contain the SiCO4 coordination unit.

A series of mono-, bis-, and tris-substituted lactamomethyl derivatives of diphenols were synthesized. The solution and solid-state structures of these compounds were confirmed by IR and NMR spectroscopy and X-ray diffraction. The in silico evaluation indicated a high probability that these compounds have various biological activities.

Silylmethylation of N-acetylvaline with the ClCH2SiMe2Cl(Me3Si)(2)NH system gave the previously unknown 2-silamorpholin-6-one derivative, whose hydrolysis in aqueous ethanol produced bis-acetylvaline-containing disiloxane. The X-ray diffraction study and quantum chemical calculations demonstrated that both silicon atoms in the final product are four-coordinated.

Pentacoordinated monofluorosilanes R1SO2NHCHR2C(O)N(Me)CH2SiMe2F containing moieties of N′-methyl-N-(organosulfonyl)-2-amino acid amides of glycine, alanine, and leucine as C,O-chelating ligands were synthesized via the reaction of corresponding disiloxanes with BF3•Et2O. The structures of obtained compounds were investigated by single-crystal X-ray diffraction analysis.

A reaction of bicyclic 2-sila-5-piperazinone, 2,2,4-trimethyl-1,4-diaza-2-silabicyclo-[4.3.0]nonan-5-one containing a proline moiety, and N-tosylglycine acyl chloride with subsequent hydrolysis of the primary unstable product to the intermediate disiloxane and its treatment with BF3•OEt2 furnished a first representative of pentacoordinate C,O-chelate halosilanes with a dipeptide fragment, namely, Ts—Gly—(S)-Pro—N(Me)CH2SiMe2F.

Bis(chelate) dichlorogermane (L8CH2)2GeCl2 (1) with the monoanionic lactamomethyl (С,О)-chelate ligand based on enantolactam (L8H) was synthesized, and its molecular and crystal structures were studied. The germanium atom is characterized by the octahedral configuration with the mutual cis-arrangement of the Cl and O atoms and trans-arrangement of the C atoms. The scheme of transformation of dichlorogermane 1 into the bis(chelate) cationic complex (L8CH2)2Ge(Cl)OTf (2) was proposed. The H-bonded complexes of dichlorogermane 1 with HOSO2CF3 and HCl assumed to be intermediates in this process were studied by quantum chemical calculation. The energy necessary for the dissociation of the H-bonded complexes to the germylium cation and HCl2 – and СlHOSO2CF3 – anions depends on the relative arrangement of the Cl atoms in the coordination polyhedron of the Ge atom. In the case of the cis-arrangement of the Cl atoms in the H-bonded complexes, the dissociation energy was estimated as 11.5—16.1 kcal mol–1.

Bis[(2,2-dimethyl-4-oxo-2 H -benzo[ e ][1,3]oxazin-3(4 H )-yl)methyl]dichlorosilane ( 1 ) and -germane ( 2 ) were synthesized by the reaction of 2,2-dimethyl-3-(trimethylsilyl)-2 H -benzo[e][1,3]oxazin-3(4 H )-one with bis(chloromethyl)dichlorosilane and -germane, respectively, taken in a ratio of 2 : 1. The structures of these compounds were determined and their stereodynamic behavior in solution was studied by multinuclear ( 1 H, 13 C, and 29 Si) and twodimensional ( 1 H, 13 C COSY, HETCOR) NMR spectroscopy. The 29 Si NMR spectroscopic study of a solution of complex 1 provides evidence that the silicon atom in this complex is pentacoordinate. The X-ray diffraction study showed that the germanium atom in complex 2 in the solid state is hexacoordinate. The permutation isomerization in the coordination units of complexes 1 and 2 was found and investigated by dynamic 1 H NMR spectroscopy. Different mechanisms of stereodynamic transformations are suggested and discussed.

NMR spectroscopy was used to study a series of C,O-monochelate N ′-(fluorodimethyl-silylmethyl)- N ′-methyl- N -(organosulfonyl)proline amides in the solid state and in solutions in chloroform, pyridine, and acetone. The structure of one of the complexes was established by X-ray crystallography. Quantum chemical calculations were performed to interpret the spectral data obtained. The molecular conformation observed in crystal was found to be retained in solutions. The coordination bonds of silicon atom with acetone and pyridine are very weak and cannot stabilize the acyclic form (without the Si-O coordination bond). The 29 Si chemical shift was found to be directly dependent on the Si-O bond distance. The mutual influence of organosulfonyl group and chelate ring was described in terms of polarization effects.

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.

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.

The reaction of amides RSO2-Pro-NHMe with ClCH2SiMe2Cl in the presence of (Me3Si)2NH gave pentacoordinated chlorosilanes RSO2-Pro-N(Me)CH2SiMe2Cl with an organosulfonyl group (R = Me, Ph, 4-ClC6H4, 4-BrC6H4, 4-MeC6H4, and 4-O2NC6H4) attached to the proline nitrogen atom. An alternative method for the preparation of these compounds comprises the cyclosilylmethylation of proline methylamide by dimethylchloromethylchlorosilane to give the previously unreported heterocyclic 2-sila-5-piperazinone system in the first step. The bicyclic silacyclane synthesized is 2-sila5-piperazinone condensed with a proline residue. The action of sulfonyl chlorides RSO2Cl leads to cleavage of the sila ring Si–N bond to give the desired chlorosilanes. The hydrolysis of these products, depending on the reaction conditions, gives either silyloxonium chlorides [RSO2-ProN(Me)CH2SiMe2OH2]Cl or disiloxanes [RSO2-Pro-N(Me)CH2SiMe2]2O. X-ray diffraction structural analysis showed that the silicon atom in the chlorides and silyloxonium chlorides is pentacoordinated due to an intramolecular O → Si bond and has distorted trigonal-bipyrimidal configuration. 29Si NMR spectroscopy showed that the disiloxanes and bicyclic sila-5-piperazinone have a tetracoordinated silicon atom.

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.