Infrared and quantum-chemical studies of the structure and vibrations of methyldisilylamine

Abstract Infrared spectra are reported from labelled species of methyldisilylamine (N(CH 3 )(SiH 3 ) 2 ) in the gas and solid phase. Quantum-chemical (QC) calculations of structure and force field have been carried out at HF, MP2 and B3LYP levels using 6-31G ∗ and 6-311G ∗∗ basis sets. The equilibrium structure belongs to the point group C s with the plane of symmetry at right angles to the NSi 2 angle and a slight non-planarity of the CNSi 2 moiety ( C s ,⊥ ). Spectra in the ν SiH region however suggest an effective C 2 v structure, with two distinct types of SiH bond. Two strong SiH bonds lie in the skeletal plane, eclipsing each other. The single ν is CH band in the CHD 2 species suggest…

Experimental Investigations and Ab Initio Studies of Tellurium(II) Dithiolates, Te(SR)2

The reaction between Te(O(i)Pr)(4) and HSR offers a new and effective route to tellurium dithiolates, Te(SR)(2). Te(S(i)Pr)(2) (1) and Te(S(t)Bu)(2) (2) are stable compounds whereas Te(SPh)(2) (3) slowly decomposes at room temperature to give Te and Ph(2)S(2). IR spectra of 1-3 and ab initio calculations (HF/3-21G(d) and MP2 with double-zeta polarization effective core potential basis set) show nu(as)(Te-S) and nu(s)(Te-S) to be around 340 and 380 cm(-)(1), respectively. UV spectra exhibit similar lambda(max) (346-348 nm) for all three compounds, with the greater extinction coefficient of 3 accounting for its different and more intense color. Analysis of the molecular orbitals of the model …

Synthesis of and structural studies on lead(II) cysteamin complexes.

The novel compounds PbCl(2).(SCH(2)CH(2)NH(3)) (1), Pb(SCH(2)CH(2)NH(2))(2).2PbCl(SCH(2)CH(2)NH(2)) (2), and Pb(SCH(2)CH(2)NH(2))(2) (3) were synthesized by reaction of PbO or PbCl(2) with [HSCH(2)CH(2)NH(3)]Cl and NaOH, and were characterized by elemental analysis, IR-, and UV/vis-spectroscopy. Single-crystal X-ray diffraction revealed different coordination modes for the two Pb atoms in 2. The Pb atom in the Pb(SCH(2)CH(2)NH(2))(2) unit forms two covalent Pb-S and two intramolecular dative Pb...N bonds, leading to a pseudo trigonal bipyramidal configuration with a stereochemically active lone pair. The Pb atom in the PbCl(SCH(2)CH(2)NH(2)) unit, the first moiety structurally characterized…

Structural chemistry of complexes of ( ? 1)d s metal ions with ?-N-donor substituted thiolate ligands (=0, 2)

Abstract The molecular structures of several d 10 metal ion complexes with 2-amino or 2-imino substituted thiolate ligands, derived from 2-aminoethanethiol, 2-(mercaptomethyl)pyridine, 2-aminobenzenethiole, and 8-mercaptoquinoline, are presented. Since ligand field stabilization energy is absent, the complexes display a large variety of co-ordination numbers and geometries around the metal centers. Distortions from ideal tetrahedral or trigonal bipyramidal configurations are discussed in terms of special structural parameters. In contrast to thiolate ligands that lack additional donor atoms and thus form oligo- or poly-nuclear complexes, the β-N donor group stabilizes mono-nuclear complexes…

Experimental and theoretical studies of the molecular and crystal structures of trialkoxy- and chlorodialkoxy-stibanes

The molecular structures of triisopropoxystibane, Sb((OPr)-Pr-i)(3), and chlorodiisopropoxystibane, SbCl((OPr)-Pr-i)(2), were determined in the solid state by single crystal X-ray diffraction. Sb((OPr)-Pr-i)(3) forms discrete centrosymmetric dimers in the solid state via Sb . . .O-Sb interactions, leading to pseudo trigonal bipyramidal configurations of the four co-ordinate Sb atoms, while SbCl((OPr)-Pr-i)(2) forms chains via Sb . . .O-Sb and Sb . . . Cl-Sb bridges, resulting in five-co-ordinate Sb atoms with pseudo octahedral configurations. Comparison of the solid state structures and the density functional optimized molecular structures of Sb(OMe)(3), SbCl(OMe)(2) and their dimers reveal…

Adducts of Tellurium Tetrachloride with Allyl Alcohol and Allyl Acetate:  1,2- vs 1,3-Addition and Structure and Dynamics of Te···O Interactions in Different Phases

The compounds Cl 3 Te[CH 2 CH(Cl)CH 2 O(H)...].Cl 2 Te[-CH 2 CH(Cl)CH 2 O-] (1) and Cl 3 Te-[CH 2 CH(CH 2 Cl)OC(CH 3 )=O...] (2) were prepared by the reaction of TeCl 4 with allyl alcohol and allyl acetate, respectively. Their molecular and crystal structures were investigated by single-crystal X-ray analysis, 1 H- 1 H-NOESY experiments, IR spectroscopy, and ab initio geometry optimization. 1 is a composite compound, whose subunits Cl 2 Te[-CH 2 CH(Cl)-CH 2 O-] (1A) and Cl 3 Te[CH 2 CH(Cl)CH 2 O(H))...] (1B) are linked in the solid state via Te...Cl-Te and O...H-O bridges. Both Te atoms are involved in similar five-membered rings, having a covalent Te-O bond in one case (1A) and a dative Te…

Cooperative Effects in Aminothiols: Acid-Base Equilibria and the Molecular Structure of 2-(N, N-Dimethylaminomethyl)thiophenol

Abstract 2-(N,N-Dimethylaminomethyl)thiophenol, (1, HL), is present as a non-zwitterionic aminothiol in the solid state, exhibiting an intramolecular S-H···N hydrogen bond. The S···N distances of the two independent molecules in the asymmetric unit are 2.929(10) and 3.050(10) Å. This structural feature is also present in an ab initio (MP2/6-31G*) optimized molecular structure. The investigation of the hydrogen bond by ab initio methods supports an n(N)-σ *(S-H) interaction as the reason for this bond type. On the basis of data from potentiometric acid-base titrations of a 0.01 M aqueous solution of [H2L]Cl with a 0.1 M aqueous solution of sodium hydroxide, values of 4.09±0.01 and 11.50±0.01…

Experimental Investigations and ab Initio Studies on Hexacoordinated Complexes of Dichlorosilane

Dichlorosilane, SiH2Cl2, forms two different kinds of coordination compounds with pyridine and 3-picoline:  the simple adduct trans-SiH2Cl2(L)2 and the ionic complex [SiH2(L)4]Cl2·4CHCl3 (L = pyridine, 3-picoline). The adducts trans-SiH2Cl2(py)2, 1, and trans-SiH2Cl2(3pic)2, 2, form directly from the reaction of bis(dichlorosilyl)methylamine, NMe(SiHCl2)2 with pyridine (py), and 3-picoline (3pic). Reaction of 1 with an excess of pyridine in chloroform yielded [SiH2(py)4]Cl2·4CHCl3, 3. The molecular and crystal structures of 1−3 were investigated by single-crystal X-ray diffraction. The Si atoms of all three compounds are hexacoordinated and lie on centers of inversion. The basic structural …

A quantum-chemical study of the structure, vibrations and SiH bond properties of disilylamine, NH(SiH3)2.

Quantum-chemical calculations at HF, MP2 and B3LYP levels with 6-31G* and 6-311G** basis sets are reported for disilylamine, NH(SiH3)2. The equilibrium structure is found to vary with both level and basis set, all but one of the structures exhibiting a small lack of planarity of the HNSi2 system. The barrier to inversion, however, is found to be very low, at most 38 cm(-1). Vibration frequencies and intensities are calculated. The frequencies are scaled, where possible, either using updated infrared data or with the aid of factors transferred from N(CH3)(SiH3)2. Unobserved frequencies due to the v(s)NSi2, deltaNSi2 and delta(perpendicular)NH modes are predicted near 610, 210 and 360 cm(-1),…

Poly[bis(μ-pentafluorobenzenethiolato)lead(II)]

The title compound, [Pb(SC6F5)2]n, exhibits a layered structure containing two differently hexa­coordinated PbII atoms. One is situated on a centre of inversion and is coordinated by six S atoms, its valence lone pair of electrons being consequently stereochemically inactive. The other Pb atom is pyramidally coordinated by three S atoms and forms three contacts to adjacent F atoms, the stereochemically active lone pair pointing towards the F3 plane.

trans-Bis(1H-benzimidazole-1-thione-κS)tetrachlorotellurium methanol disolvate

The Te atom in the title complex, trans-[TeCl4(C6H4N2H2CS)2]·2CH4O or C16H20Cl4N4O2S2Te, occupies a special position at a crystallographic inversion centre and has an octahedral coordination formed by four chloro ligands and the S atoms of two benz­imidazole–thione mol­ecules. The hydrogen-bond system involving the disordered solvent methanol mol­ecules links the tellurium complexes into the infinite two-dimensional aggregates in the crystal.

Synthesis and Structural Characterization of (1,4-Dihydropyrid-1-yl)aluminum Complexes

The reaction between LiAlH(4) and pyridine, 4-methylpyridine, or 3,5-dimethylpyridine results in hydride transfer to the pyridine ring to give tetrakis(pyridine)lithium tetrakis(1,4-dihydropyrid-1-yl)aluminate(III), 1, tetrakis(4-methylpyridine)lithium tetrakis(1,4-dihydro-4-methylpyrid-1-yl)aluminate(III), 2, or tetrakis(3,5-dimethylpyridine)lithium tetrakis(3,5-dimethyl-1,4-dihydropyrid-1-yl)aluminate(III), 3, respectively. We claim that 1, instead of lithium tetrakis(1,4-dihydropyrid-1-yl)aluminate(III), is the compound which is known as Lansbury's reagent. Treatment of trimethylamine-alane, AlH(3).NMe(3), with pyridine yields tris(1,4-dihydropyrid-1-yl)(pyridine)aluminum, 4. It could be…

Molecular structure of Te(OMe)4.ClTe(OMe)3, a model for ligand exchange between Te(IV) centers.

ClTe(OiPr)3 could be prepared from stoichiometric amounts of TeCl4 and Te(OiPr)4, a reaction that requires the exchange of ligands between different Te centers. Ligand redistribution between telluranes was studied, and rapid exchange of -Cl and -OR (R = Me, iPr) ligands in solutions of several binary mixtures of Te(OMe)4, Te(OiPr)4, ClTe(OMe)3, and ClTe(OMe)3, and ClTe(OiPr)3 was established by multinuclear NMR spectroscopy. The solid-state structure of Te(OMe)4.ClTe(OMe)3, the first structurally characterized adduct between different telluranes, was investigated by single-crystal X-ray diffraction. It exhibits a very short Te-O...Te bridge between the two Te centers and additional Te...O a…

Cysteamine and its homoleptic complexes with group 12 metal ions. Differences in the coordination chemistry of ZnII, CdII, and HgII with a small N,S-donor ligand.

2-Ammoniumethanethiolate, (-)SCH(2)CH(2)NH(3)(+), the first structurally characterized zwitterionic ammoniumthiolate, is the stable form of cysteamine (HL) in the solid state and in aqueous solution. Reactions of ZnCl(2), Cd(Oac)(2), and HgCl(2) with cysteamine and NaOH in a 1:2:2 ratio, respectively, lead to the homoleptic complexes ML(2). Their single-crystal X-ray structures demonstrate basic differences in the coordination chemistry of Zn(II), Cd(II), and Hg(II). While chelating N,S-coordination modes are found for all metal ions, Zn(II) forms a mononuclear complex with a distorted tetrahedral Zn(N(2)S(2)) coordination mode, whereas Hg(II) displays a dimer with Hg(N(2)S(2)) coordinated …

Formation of meso-1,2-Bis(dimethylamino)-1,2-diphenylethane by Oxidative C-C Coupling Reaction

The title compound was obtained from the reaction of N,N-dimethylbenzylamine with n-butyl lithium and sulfur in tetrahydrofuran at room temperature. Its molecular structure was investigated by means of single crystal X-ray diffraction and quantum chemical DFT methods. The formation of meso-1,2-bis(dimethylamino)-1,2-diphenylethane is likely to be due to an unusual α-deprotonation of N,N-dimethylbenzylamine, instead of the well known ortho-lithiation, with a subsequent oxidative C-C coupling of the anions. Ab initio calculations of the corresponding α- and o-deprotonated anions of N,N-dimethylbenzylamine showed the former to be more stable than the latter, due to delocalisation of the negati…

Structural diversity within analogous compounds: syntheses and studies of M(SCH2CH2NH2)Cl (M = Zn, Cd, Hg).

The novel complexes [Zn(L)Cl] (1), [Cd(L)Cl] (2), [Hg(L)Cl] (3), {[Hg(L)Cl]·NaOH·2H 2 O} (3·NaOH·2H 2 O), and {[Hg 3 (HL) 2 Cl 6 ]·2H 2 O} (4) (L = -SCH 2 CH 2 NH 2 ) were prepared and investigated by means of IR spectroscopy and single-crystal X-ray diffraction. The crystal structures of 1, 2, and 3·NaOH·2H 2 O show chelating N,S-coordination of the cysteaminate ligand, bridging S, and terminally coordinating Cl. Apart from these common features, the coordination geometries and modes of intermolecular association are different. 1 forms a cyclic tetramer with a Zn 4 S 4 ring, and 3·NaOH·2H 2 O contains one-dimensional [Hg(L)Cl] n chains with S-bridged Hg atoms. Zn and Hg atoms in 1 and 3·Na…

Molecular and Crystal Structures of TeCl4-Allylalcohol and -Allylacetate Adducts

Bis(dichlorosilyl)methylamine - Synthesis, Crystal Structure, and Conformational Analysis in the Gas Phase

A straightforward preparation has been found for bis(dichlorosilyl)methylamine, (SiHCl2)2NMe (1), involving reaction between H2NMe and an excess of SiHCl3, dissolved either in pentane or THF at 253 K. 1 and a side-product, 1,3,5-trichloro-2,4,6-trimethylcyclotrisilazane, (–SiHCl–NMe–)3 (2), were identified by elemental analysis, mass spectrometry and 1H-NMR-spectroscopy. Some physical, NMR- and IR spectroscopical properties of 1 were determined. The molecular and crystal structure of 1 was investigated by single crystal X-ray diffraction. Selected structural parameters: r(Si–N) 169.7(5), r(Si–Cl) 203.1(2)–204.4(2), r(C–N) 150.0(8) pm; a(SiNSi) 123.6(3), a(SiNC) 118.3(4)/118.0(4)°. Ab initio…

PyridiniumD(+)-10-camphorsulfonate hemihydrate

In the crystal structure of pyridinium d(+)-10-camphor­sulfonate hemihydrate, C5H6N+·C10H15O4S−·0.5H2O, a water mol­ecule lying on a twofold axis serves as a donor of two hydrogen bonds, thus linking two camphor­sulfonate anions. Each anion in its turn acts as a hydrogen-bond acceptor for the NH group of a pyridinium cation.

Ab Initio Studies of Disilazanes:  Structures and Vibrational Properties of Hexachloro-, Hexamethyl-, and Tetrachlorodisilazane

The structures of hexachlorodisilazane, NH(SiCl3)2, and hexamethyldisilazane, NH(SiMe3)2, have been calculated at HF/6-31G* and MP2/6-31G* levels. Both contain planar HNSi2 skeletons and show the expected staggering of the substituents as seen along the Si‚‚‚Si direction, as previously found in the electron diffraction structure of the hexamethyl compound. Unlike the latter, however, the ab initio structures both belong to the C2 point group. Force fields for these two molecules and for tetrachlorodisilazane, NH(SiHCl 2)2, were calculated at the HF level and scaled to produce vibration frequencies for comparison with previously obtained spectra. For NH(SiCl3)2, all but five of the fundament…

Halogen exchange and expulsion: ligand stabilized dihalogen silicon dications

The first ligand stabilized SiCl22+ dications were synthesized using N-methylimidazole as co-ordinating ligand. The compounds SiCl4, SiBr2Cl2, and SiH2Cl2 form six-co-ordinated dicationic compounds of almost octahedral symmetry with similar structures which were investigated by single crystal X-ray analysis and density functional calculations. The structures exhibit particularly short dative Si–N bonds of about 1.90 A. Complexes crystallized from the same solvent are isostructural. A different solvent, though, leads to geometrical variations. It was also discovered that the halogen exchange process among mixed silicon tetrahalides occurs under much milder conditions than previously thought …

Conformation versus coordination: synthesis and structural investigations of tellurium(II) dithiolates derived from beta-donor-substituted thiols.

New methods of preparing tellurium(II) dithiolates, Te(SR)(2), are presented. Te(SCH(2)CH(2)OAc)(2), 1, was made from Te(SCH(2)CH(2)OH)(2) by acetylation of the hydroxyl groups. Te(SCH(2)CH(2)SAc)(2), 2, [Te(SCH(2)CH(2)NH(3))(2)]Cl(2), 3, and Te(SC(6)H(4)(o-NH(2)))(2), 4, were synthesized by ligand exchange reactions of Te(S(t)Bu)(2) with 2 equiv of HSCH(2)CH(2)SAc, [HSCH(2)CH(2)NH(3)]Cl, and HSC(6)H(4)(o-NH(2)), respectively. Of all compounds, 4 exhibits the strongest thermal sensitivity toward decomposition and the largest low-field shift of the (125)Te NMR signal, two features that are attributed to weak Te.N interactions. The structural parameters of the CSTeSC unit exhibit very similar…

Tellurium(IV) Tetraalkoxides and Chlorotellurium(IV) Alkoxides Derived from β-Donor Alcohols

Funktionalisierte Tellur(II)-thiolate: Tellurbis(2-hydroxyethanthiolat)-Hydrat, der erste H2O-TeII-Komplex

Ethanedithiol diacetate

Ethane-1,2-diyl S,S′-bis­(thio­acetate), H3CC(O)SCH2CH2SC(O)CH3 or C6H10O2S2, forms centrosymmetric mol­ecules in the solid state and the molecular structure determined by X-ray crystallography is in good agreement with that obtained by density functional geometry optimization. The planarity of the O=C—S—C fragment, which is also found in structures of other thio­acetates, is attributed to a strong np(S)–π*(C—O) orbital interaction.

Molecular “Floppyness” and the Lewis Acidity of Silanes: A Density Functional Theory Study

A comprehensive set of Lewis acid-base adducts of silanes was investigated by means of the density functional theory geometry optimization [B3LYP/6−31G(d)], and thermochemical calculations, [B3LYP/6−311+G(2d,p)//B3LYP/6−31G(d)]. Complex formation was found to weaken Si−Cl and Si−Br bonds more than Si−F or Si−H bonds. Comparable distances between Si and a Lewis base L (L = NH3, OH2, F−) are shorter in hexa- than in pentacoordinated complexes. The molecular structures of the pentacoordinated Si complexes allowed for a mapping of an SN2 reaction pathway by correlating the lengths of the Si−X and Si−L bonds. Complex formation was found to be exothermic for most of the coordination compounds, an…

Functionalized Tellurium(II) Thiolates: Tellurium Bis(2-hydroxyethanethiolate) Hydrate, the First H2O–TeII Complex

Tellurium( II ) Dialkanethiolates: n p (S)‐σ*(Te−S′) Orbital Interactions Determine the 125 Te NMR Chemical Shift, and the Molecular and Crystal Structure

Tellurium(II) dimethanethiolate, Te(SMe)(2), and tellurium(II) diethanethiolate, Te(SEt)(2), were synthesized by reaction of TeO2 and Te(OiPr)(4) with HSMe and HSEt, respectively. In the solid state, Te(SMe)(2) exhibits a cis-conformation of the methyl groups with respect to the TeS2 plane - an unprecedented situation for nonfunctionalized organotrichalcogenides - whereas Te(SEt)(2) shows a trans-conformation. Ab initio calculations performed for Te(SMe)(2) and Te(SEt)(2) show that the cis- and trans-conformers represent minima on the potential energy surface and are stabilized by intramolecular pi-type n(S)-sigma* (Te-S') orbital interactions. In the solid state, the molecules of each comp…

Spectroscopic Investigation of the System TeCl4/[NEt4]PF6 in Solution and the Crystal Structure of [NEt4]2[Te2Cl10].

Solutions containing TeCl 4 and [NEt 4 ][PF 6 ] in CH 2 Cl 2 were investigated by means of UV/vis and NMR spectroscopy in order to study the complex chemistry of TeCl 4 with the [PF 6 ] - anion. The results show formation of [TeCl 5 ] - and strong interactions of [PF 6 ] - with a tellurium containing species, presumably [TeCl 3 ] + . The life time of the Te I V -PF 6 complex is long enough to give different signals in the 1 9 F NMR spectrum of a solution containing excess [PF 6 ] - . Even a fivefold excess of Cl - ions over [PF 6 ] - does hardly lead to a dissociation of [TeCl 3 ...PF 6 ]. Crystals of [NEt 4 ] 2 [Te 2 Cl 1 0 ] were obtained from a 4:1 solution of [NEt 4 ]PF 6 and TeCl 4 in …

Molecular structures of Se(SCH3)2 and Te(SCH3)2 using gas-phase electron diffraction and ab initio and DFT geometry optimisations

The molecular structures of Se(SCH3)2 and Te(SCH3)2 were investigated using gas-phase electron diffraction (GED) and ab initio and DFT geometry optimisations. While parameters involving H atoms were refined using flexible restraints according to the SARACEN method, parameters that depended only on heavy atoms could be refined without restraints. The GED-determined geometric parameters (rh1) are: rSe-S 219.1(1), rS-C 183.2(1), rC-H 109.6(4) pm; S-Se-S 102.9(3), Se-S-C 100.6(2), S-C-H (mean) 107.4(5), S-Se-S-C 87.9(20), Se-S-C-H 178.8(19)° for Se(SCH3)2, and rTe-S 238.1(2), rS-C 184.1(3), rC-H 110.0(6) pm; S-Te-S 98.9(6), Te-S-C 99.7(4), S-C-H (mean) 109.2(9), S-Te-S-C 73.0(48), Te-S-C-H 180.…