Metallomethanes: XII. Vibrational spectra and force fields of methylmercurimethanes

The vibrational spectra data, the assignments, and the results of normal coordinate calculations for CH_{4 − n}(HgCH₃)_n molecules (2 ⩽ n ⩽ 4) are reported. The central CHg valence force constants are 1.870, 1.653, and 1.582 N cm⁻¹ while the terminal ones are 2.121, 2,101, and 2.160 N cm⁻¹ for n = 2, 3 and 4, respectively. The latter values are 12, 21, and 27% higher than the central CHg force constants, but all of them are substantially lower than those in dimethylmercury (2.379 N cm⁻¹). These findings can be accounted for in terms of increasing shift of electron density towards the periphery of these molecules and increasing non-bonded metal-metal interaction. The nature of the normal modes is discussed.     

Vibrational spectra,force fields and NMR-data for triorganyl-tetrelomethanes CH4−n(TtR3)n (Tt = Sn and Pb)

Based on vibrational spectra normal coordinate calculations have been carried out for trimethyltetrelomethanes CH_4−n(TtMe₃)_n (Tt = Sn and Pb, n = 2 and 4). The resulting comparable force constants of the two distinguishable types of carbon-metal bonds for Tt = Sn (range K(C-Sn) 220 - 180 Nm⁻¹) are 10 – 15% higher than for Tt = Pb (K(C-Pb) 190 - 170 Nm⁻¹). These force constants K(C-Tt) are similar to the K(C-Hg) values of corresponding methylmercuriomethanes CH_4−n(HgMe)_n. The force constants K (C-Tt), and also the coupling constants ¹J(Tt,C) from NMR spectra, indicate weakening of the carbon-metal bonds in the central CTt_n groups with growing n, whereas the peripheral TtMe bonds are almost unaffected by variations of n.     

Infrared spectra of Pt(II) creatinine complexes. Normal coordinate analysis of creatinine and Pt(creat)2(NO2)2

Infrared spectra of creatinine (H₃CNC(NH)NHCOCH₂) (creat), cis-Pt(creat)₂(NO₂)₂ and Pt(creat)₄(CIO₄)₂ have been recorded in the range 50–4000 cm⁻¹. The fundamental vibrations for the creatinine molecule were assigned by normal coordinate analysis in the generalized valence force field approximation. The spectrum of cis-Pt(creat)₂(NO₂)₂ was interpreted by comparison with the creatinine vibrational modes. Additionally the Pt(creat)₄(ClO₄)₂ infrared spectrum has been involved to help the assignment.     

Mononuclear carbonyl manganese(I) and molybdenym(II) complexes with chelating biimidazole,bibenzimidazole or tetramethylbiimidazole ligands

The preparations and properties are described of novel anionic and neutral mononuclear biimidazolate (biim), bibenzimidazolate (bibzim), or tetramethylbiimidazolate (tmbiim) manganese(I) and molybdenum(II) complexes of the type [Et₄N][Mn(CO)₂L₂(bibzim)] (L = P(OEt)₃); [Et₄N][Mo(η⁵-C₅H₅)(CO)₂-(N)₂] ((N)₂²⁻ = biim²⁻, bibzim²⁻ tmbiim²⁻); [Mn(CO)_4−nL_n{H(N)₂}] (n = 1; H(N)₂⁻ Hbibzim⁻; L = P(OMe)₃, PEt₃), (n = 2; H(N)₂⁻ = Hbiim⁻, Hbibzim⁻; L = P(OPh)₃, P(OMe)₃, P(OEt)₃, P(OⁱPr)₃; [Mo(η⁵-C₅H₅)(CO)₂{H(N)₂}] (H(NN)₂⁻ = Hbiim⁻, Hbibzim⁻, Htmbiim⁻, in which the heterocyclic anions act as bidentate chelate groups. Treatment of the anionic complexes with MeI gives neutral derivatives of general formula [Mn(CO)₂L₂(Mebibzim)] (L = P(OMe)₃, P(OEt)₃) and [Mo(η⁵-C₅H₅)(CO)₂{Me(N)₂}] (Me(N)₂⁻ = Me-biim⁻, Mebibzim⁻, Metmbiim⁻. Cationic manganese(I) complexes of the type [Mn(CO)_4−nL_n{H₂(N)₂}][ClO₄ (n = 1; H₂ (N)₂ = H₂bibzim; L = P(Ome)₃, PEt₃), (n = 2; H₂(N)₂ = H₂biim, H₂bibzim; L = P(OPh)₃, P(OMe)₃, P(OEt)₃, P(OⁱPr)₃) have also been obtained by treating the corresponding neutral complexes with HClO₄. The structures of the complexes have been elucidated by molecular weight determinations, conductance data, and IR spectroscopy.     

A proton and carbon-13 nuclear magnetic resonance study of neopentylmercury compounds

Substituent effects on ¹⁹⁹Hg¹H and ¹⁹⁹Hg¹³C spinspin coupling constants have been studied for neopentylmercury derivatives, (CH₃)₃CCH₂HgR(or X), where R is covalently bonded Me, Et, t-Bu, neopentyl, and vinyl, and X is easily ionizable CN, Br, Cl, OCOCH₃, and ONO₂. Linear relationships exist between the methylene J(¹³CH) and ²J(HgH), ⁴J(HgC) and ²J(HgC) and ³J(HgC); but deviations from linearity occur for the chloride, bromide, acetate, and nitrate in the relationships between ²J(HgH) and ⁴J(HgH), ²J(HGH) and ²J(HGC). These deviations are discussed in terms of hyperconjugative p_πd_π bonding between the methylene CH bonds and mercury.     

Determination of ion association constants by means of IR absorption band intensities of the molecules forming the first coordination spheres of the cations

The IR spectra of the binary systems CH₃CNLiI, CH₃CNLiClO₄ and CH₃CNLiNCS in the regions of the stretching vibrations of CC and CN bonds of acetonitrile have been recorded. The association constants have been determined on the basis of the analysis of the IR absorption band intensities of acetonitrile molecules. The values of the absorption coefficients of the molecules forming the first coordination spheres of Li⁺ cations have been estimated.     

Fourier-transform Raman and infrared spectra and normal coordinate analysis of (C6H5)2BiCl and [N(CH3)4]+[(C6H5)2BiCl2]−

The vibrational properties of the diphenylbismuth(III) chloride compounds (C₆H₅)₂BiCl and [N(CH₃)₄]⁺[(C₆H₅)₂BiCl₂]⁻ have been investigated. A comprehensive assignment of the fundamental modes in the measured Fourier-transform Raman and infrared spectra has been carried out. Normal coordinate calculations of these compounds based on new X-ray crystal structure data have been performed to identify the BiCl stretching and bending vibrations of both compounds. For [N(CH₃)₄]⁺[(C₆H₅)₂BiCl₂]⁻ in the solid state, the ν_s(BiCl₂) and ν_as(BiCl₂) occur at 215 cm⁻ (Raman) and 237 cm⁻ (Raman), respectively, in good agreement with the calculated wavenumbers. The force constant calculation yields a BiCl stretching force constant of 0.89 × 10² N m⁻¹.     

Über Antimon-haltige Heterocyclen—IV. Schwingungsspektren von phenylierten Oxadithia- und Trithiastibocanen, -bismocanen, -stannocanen und -plumbocanen

The i.r. and Raman spectra of the cyclic dithiolates Ph_nM(SCH₂CH₂)₂X (n = 1, M = Sb, Bi; n = 2, M = Sn, Pb; X = O, S) are reported (3200-100 cm⁻¹). The spectra are very similar for both X = O and X = S. The pentadeuterophenylated antimony analogues (Ph-d₅)Sb(SCH₂CH₂)₂X make it possible to separate signals originating from vibrations of the phenyl groups, of the aliphatic ring parts and of the coordination polyhedra around M, respectively.     

Synthesis and structural characterization of a polar Os(II,III) complex,Os2(fhp)4Cl

The title compound was prepared by prolonged reaction of Os₂(CH₃COO)₄Cl₂ with Hfhp (Hfhp = 6-fluoro-2-hydroxypyridine) in refluxing toluene in the presence of LiCl. The product, Os₂(fhp)₄Cl (1), is a result of ligand displacement with a concomitant core reduction of Os₂⁶⁺ to Os₂⁵⁺. Crystals were grown by slow diffusion of hexane into a dichloromethane solution of 1. Crystallographic data are as follows: tetragonal crystal system, space group I4mm (No. 107), a = b = 11.000(3) Å, c = 13.142(2) Å, V= 1590(1) ų, Z = 2. The molecule possesses crystallographic 4mm symmetry, with the OsOs bonds lying along the four-fold axes. The four fhp ligands are arranged in a polar fashion around the diosmium core, blocking one axial site. The second axial position is occupied by a chloride ion. The principal distances in 1 are: Os(1)Os(2) = 2.341(1) Å, Os(1)N = 2.027(12) Å, Os(2)O = 2.014(5) Å, Os(2)Cl = 2.487(7) Å. The title compound was also investigated by several physical methods. The electrochemistry as determined by cyclic voltammetry revealed two processes: a reversible, one-electron reduction at E_ox = −0.63 V in dichloromethane and an irreversible oxidation at E_ox = +0.95 V in dichloromethane vs Ag-AgCl at room temperature. The electronic spectrum shows strong bands at 413 nm (ε = 4290 M⁻¹ cm⁻¹), 309 nm (ε = 23,560 M⁻¹ cm⁻¹) and at 294 nm (ε = 26,500 M⁻¹ cm⁻¹) as well as shoulders at 334 and 261 nm.     

The tricyanomercurate(II) ion

The tricyanomercurate(II) ion, [Hg(CN)₃]^?, is isolated in the form of its solid caesium salt from a 1:1:1 ethanolic solution of CsF, KCN and Hg(CN)₂, and characterised by IR and Raman vibrational spectroscopy. Assignments are made for the CN and HgC stretching vibrations and the HgCN bending vibrations. The spectra are consistent with the [Hg(CN)₃]^? ion occupying a site of C₁ symmetry.     

Force constants in molecular crystals of methyl-and perdeuteriomethylmercury(II) halides

Force constants for the internal vibrations involving the metal and for the lattice vibrations of Hg(CH₃)X and Hg(CD₃)X (X = Cl, Br or I) are calculated on the basis of a D_4h⁷ layer structure. The internal HgX stretching force constants are much lower than for these molecules in solution, but HgC stretching force constants are slightly higher. The HgX and longitudinal translatory force constants within the lattice layer are close in value to the strong and weak HgX bond stretching force constants respectively in the unsymmetrical [Hg(CH₃)X₂]^? complex ions.     

Structure et étude raman du composé (C3H7NH3)2HgCl4

The structure of (C₃H₇NH₃)₂HgCl₄ is orthorhombic, M_r = 462.6, Abma, a = 7.991(2) Å, b = 7.779(2) Å, c = 23.519(2) Å, Z = 4, V = 1462(1) ų, D_m = 2.05(2), D_x = 2.10 mg/m⁻³, λ(AgKα) = 0.56083 Å, μ(AgKα) = 61.02 cm⁻¹, T = 300 K, R = 0.032, R₂ = 0.027 for 1188 reflections with I < 0.5σ(I). The structure is of the K₂NiF₄ type and consists of HgCl₆ octahedra which are held together through equatorial Cl atoms forming a two-dimensional (HgCl₄)²⁻_n layer perpendicular to the c axis (HgCl_ax is shorter than the HgCl_eq). The C₃H₇NH⁺₃ cations inserted between these layers are disordered and joined to the layers by hydrogen bonding. The Raman spectra between 10 and 400 cm⁻¹ have been recorded and some characteristic (HgCl₄)²ⁿ⁻_n layer frequencies assigned. Thermal analysis indicates two singularities at 195 and 205 K.     

The anharmonic force constant K234 of CH3CN in different phases,solvents and complexes with Lewis acids

The Fermi coupling coefficient W and the anharmonic force constant K₂₃₄ of CH₃CN have been determined from i.r. and Raman studies of the v₂—v₃+v₄ Fermi doublet in liquid and gaseous phases, solutions in inert, basic and acidic solvents and in crystalline complexes with Lewis acids. The values of these parameters have been calculated by a modification of the Winther method. This method is also applied to gas phase data of the isotopic speices ¹³CH₃CN, CH₃ ¹³CN and CH₃C¹⁵N. Values of W are approximately 13±1 cm⁻¹ except for basic and inert solvents where they are approximately 18 cm⁻¹.     

Composes isomorphes MeX2O4E2: I. Etude vibrationnelle de MnSb2O4 entre 4 et 300 K: champ de force et tenseur élastique

A vibrational study of the tetragonal antimony oxides (Mn, Ni, Zn) Sb₂O₄E₂ in which E is a lone pair has been carried out using Raman and infrared spectroscopy between 4 and 300 K. A force field calculation has been performed using previous results (J. P. Vigouroux et al., Spectrochimi. Acta A 38, 393, 1982) and a new structural evolution approach using models and results of X-ray and neutron diffraction experiments (R. Chater and J. R. Gavarri, J. Solid State Chem. 59, 123, 1985). This approach delivers mean force constants F_a, F_c, elastic constants C_ij, and Grüneisen parameters. Using these results it has been possible to propose initial force constants which have been refined. For MnSb₂O₄ the following results are obtained: (1) In MnO₆ octahedra, the six MnO bond force constants are about 60 N m⁻¹. (2) In SbO₃E tetrahedra, the three SbO force constants are about 200 N m⁻¹ while OSbO angle force constants are in the range 50–70 N m⁻¹. (3) SbE · · · SbE interactions are evaluated in the three Mn, Zn, Ni isomorphous compounds: the interaction is strongly connected with the SbSb distances found in these structures. It is shown that the force field calculation is in agreement with the results of the structural evolution approach: the values F_a = 49 N m⁻¹, F_c = 70 N m⁻¹ can be compared qualitatively with the various averaged force constants.     

Intramolecular easily polarizable hydrogen bonds with anilides of 1-piperidine carboxylic acids

IR spectra are plotted from anilides of 1-piperidine carboxylic acids C₅H₁₀N(CH₂)_n CONHC₆H₄R in CHCl₃ and CDCl₃ solutions. In the cases of n = 1 and n = 4, weak intramolecular (NH?N) hydrogen bonds are formed. An asymmetrical energy surface occurs and the proton is present at the N of the anilide group. In the cases of n = 2 and n = 3, intramolecular proton transfer hydrogen bonds of the types N_BH?N_P ? ^?N_B?H⁺N_p are formed. In contrast to the intramolecular OH? N ? O^?1 ? H⁺N bonds with 1-piperidine carboxylic acids, these bonds to not cause IR continua but two bands: one in the region 3250–3190 and one in the region 2500–2450 cm^?1. The fact that, instead of IR continua, bands are observed is explained by the following: (1) these hydrogen bonds are relatively long; (2) they show only a narrow distribution of bond length; (3) the electrical fields at these bonds are small, since they are strongly screened.     

Stabilization of Pancake Bonding in (TCNQ)2.− Dimers in the Radical-Anionic Salt (N−CH3−2-NH2−5Cl−Py)(TCNQ)(CH3CN) Solvate and Antiferromagnetism Induction

We report a new antiferromagnetic radical-anion salt (RAS) formed from 7,7,8,8-tetracyanquinonedimethane (TCNQ) anion and 2-amino-5-chloro-pyridine cation with the composition of (N−CH₃−2-NH₂−5Cl−Py)(TCNQ)(CH₃CN). The crystallographic data indicates the formation of (TCNQ)₂^.− radical-anion π-dimers in the synthesized RAS. Unrestricted density functional theory calculations show that the formed π-dimers characterize with strong π-stacking “pancake” interactions, resulting in high electronic coupling, enabling efficient charge transfer properties, but π-dimers cannot be stable in the isolated conditions as a result of strong Coulomb repulsions. In a crystal, where (TCNQ)₂^.− π-dimers bound in the endless chainlets via supramolecular bonds with (N−CH₃−2-NH₂−5-Cl−Py)⁺ cations, the repulsion forces are screened, allowing for specific parallel π-stacking interactions and stable radical-anion dimers formation. Measurements of magnetic susceptibility and magnetization confirm antiferromagnetic properties of RAS, what is in line with the higher stability of ground singlet state of the radical-anion pair, calculated by means of the DFT. Therefore, the reported radical-anion (N−CH₃−2-NH₂−5Cl−Py)(TCNQ)(CH₃CN) solvate has promising applications in novel magnetics with supramolecular structures.     

Raman spectroscopic study of (CH3NH3)2HgCl4 in the high-temperature range

A Raman spectroscopic study of (CH₃NH₃)₂HgCl₄ is reported in the temperature range 299–373 K. Discontinuities in the HgCl symmetric stretching mode and in the frequency shift of the CN stretching mode indicate a new phase above 330 K. A non-linear increment of the widths of these bands confirms the transition. Arrhenius behaviour of the CN stretching mode indicates a barrier of 1234 cm⁻¹.     

A multinuclear NMR spectroscopy study of alkoxysilanes

¹⁷O, ²⁹Si, and ¹³C NMR spectra of more than 100 mono-, di-, tri- and tetra-alkoxysilanes R_4−nSi(OR′)_n; R = C_nH_2n+1, Ph, CH₂Cl, CH₂Br; R′ = C_nH_2n+1, CH₂Ph, CH₂CH₂Cl, CH₂CHCH₂, CH₂CCH, CH₂CF₃. (CH₂)₃Cl, (CH₂)₃CN have been studied.Linear relationships between the chemical shifts of ¹⁷O, ²⁹Si, ¹³C in alkoxysilanes and the inductive and steric constants of substituents R and R′ were observed. Different transmission of electronic effects along the SiO bond in various directions was revealed by means of ¹³C, ²⁹Si, ¹⁷O NMR spectroscopy and correlation analysis. The results are discussed in terms of (pd)_π-bonding between the oxygen and silicon atoms in compounds containing an SiO bond.     

Generation and characterization of C60(CN)2n−(n=1,2,3)

The mono-anion, di-anion and tri-anion of dicyanodihydrofullerene [C₆₀(CN)₂] have been generated and monitored with a thin-layer spectro-electrochemical cell. The characteristic NIR absorption bands are found to be at 1019, 875 as well as at 744, and 691 nm for C₆₀(CN)₂⁻, C₆₀(CN)₂²⁻ and C₆₀(CN)₂³⁻, respectively. Density functional theory calculations indicate that these anions exhibit no Jahn–Teller effect and possess charge distributions and shape distortions that are different from C₆₀ⁿ⁻(n=1,2,3) upon negative charge addition.     

Vibrational spectra and normal coordinate analyses of the trimethyloxonium and trimethylammonium cations

Raman and i.r. spectra of the compounds (CH₃)₃O⁺ SbCl⁻₆ and (CH₃)₃NH⁺ SbCl⁻₆ are reported and assigned. Normal coordinate calculations support the vibrational assignments for the cations Of C_3v symmetry, and yield force constants k(CO) = 4.05 mdyn·Å⁻¹ and k(CN) = 4.80 mdyn·Å⁻¹ for the trimethyloxonium ion and the trimethylammonium ion, respectively.