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Showing papers on "Tetrahedral molecular geometry published in 1985"


Journal ArticleDOI
TL;DR: The structure of PR3Se was solved using multisolution direct methods and refined by least squares to R 0.038 (R′ 0.041) for 1 030 observed diffractometer data as discussed by the authors.
Abstract: Crystals of PR3Se (R = 2-furyl) are monoclinic, space group Cc, with a= 11.720(6), b= 12.527(9), c= 8.569(5)A, and Z= 4. The structure was solved using multisolution direct methods and refined by least squares to R 0.038 (R′ 0.041) for 1 030 observed diffractometer data. Phosphorus adopts a distorted tetrahedral geometry with mean Se–P–C and C–P–C angles of 114.9 and 103.4°, respectively. The molecule has almost ideal C3 symmetry. The C–P–C angle is the smallest reported for a tertiary phosphine selenide. The average P–C bond length [1.778(6)A] and the P–Se bond length (2.094 A) are both considerably shorter than found in other arylphosphine selenides. The oxygen atoms of the 2-fury1 groups are arranged about the selenium atom, with an average Se ⋯ O distance of 3.577 A. 77Se N.m.r. studies show that the selenium atom is shielded by 86 p.p.m. compared with that in triphenylphosphine selenide, implying a ‘through-space’ interaction involving the 2-fury1 oxygen atoms. Selenium-77 chemical shifts have also been determined for a range of heteroaryl-and substituted phenyl-phosphine selenides. Whereas the 2-furyl group causes the selenium to become shielded, the related 2-thienyl group causes it to become deshielded. Deshielding of selenium is also experienced on introduction of ortho substituents in arylphosphine selenides. Thus, for example, the selenium atom of tris(2,4,6-trimethoxyphenyl)phosphine selenide is deshielded by 240 p.p.m. compared with that in triphenylphosphine selenide. Possible origins of these effects are considered.

54 citations


Journal ArticleDOI
TL;DR: In this article, the synthesis and characterization of transition-metal co-ordination compounds containing the newly synthesized ligand NN-bis(3,5-dimethylpyrazol-1 -ylmethyl)aminobenzene (bdmpab) are described.
Abstract: The synthesis and characterization of transition-metal co-ordination compounds containing the newly synthesized ligand NN-bis(3,5-dimethylpyrazol-1 -ylmethyl)aminobenzene (bdmpab) are described The compounds have the general formulae [M (bdmpab)X2](M = Co, Cu, or Zn; X = Cl or Brand M = Co; X = SCN or NO3) and [Cu2(bdmpab)(SCN)3] and have been characterized by several spectroscopic methods and analytical techniques In some compounds (viz M = Co or Zn; X = Cl or Br and M = Co; X = SCN or NO3) bdmpab acts as a bidentate ligand and in others (viz M = Cu; X = Cl, Br, or SCN) as a tridentate ligand In all compounds the anions are also bonded Because of the flexible character of the ligand the preference of the transition-metal ions for specific co-ordination geometries is reflected in the resulting co-ordination compounds To prove the chelating nature of the ligand, and in particular to find out whether or not the aniline nitrogen is co-ordinated, the crystal structures of two representative examples have been determined [Co(bdmpab)Cl2] crystallises in space group Pbca, with a= 8713(2), b= 17252(4), c= 27626(7)A, and Z= 8 Standard least-squares refinement gave R= 0031 (R′= 0028) The cobalt atom has a CoN2Cl2chromophore in a distorted tetrahedral geometry Co–N distances are 2038(2) and 2044(2)A for the pyrazole nitrogens The Co ⋯ N contact of 3854(2)A for the aniline nitrogen is considered as non-co-ordinating Co–Cl distances are 22434(8) and 22266(8)A [Cu(bdmpab)Br2] crystallises in space group P21/n, with a= 8742(3), b= 29408(5), c= 8522(1)A, β= 10777(2)°, and Z= 4 Standard least-squares refinement gave R= 0025 (R′= 0026) The copper atom has a CuN3Br2 chromophore in a distorted trigonal-bipyramidal geometry The pyrazole nitrogens occupy the axial positions Cu-N distances are 1988(5) and 1981(5)A for the pyrazole nitrogens and 2423(1)A for the aniline nitrogen Cu–Br distances are 2454(1) and 2414(1)A

49 citations


Journal ArticleDOI
TL;DR: The title complex of ZnCl2(C5H9NO2)2, F.W.55, was prepared at pH 4.0 by X-ray diffraction.
Abstract: The title complex was prepared at pH 4.0. The crystal and molecular structures have been determined by X-ray diffraction. The crystals of ZnCl2(C5H9NO2)2, F.W.=366.55, were orthorhombic: space group P212121, a=13.527(3), b=16.263(3), c=6.598(1) A, U=1451.4(5) A3, Z=4, Dm=1.67 g cm−3, Dx=1.68 g cm−3, and μ(Mo Kα)=21.2 cm−1. The zinc atom is coordinated in a tetrahedral geometry to two chlorine atoms and the two carboxyl oxygen atoms of two L-proline ligands. Each L-proline is coordinated as a monodentate ligand.

47 citations


Journal ArticleDOI
TL;DR: The single crystal X-ray structures of (CuICH3CN4·dibenzo-18-crown-6 (I) and (Cuich3CN) (II) have been determined at room temperature as discussed by the authors.

24 citations


Journal ArticleDOI
TL;DR: In this article, the I.R. lines in this region have been assigned, the effective rotational constants being 5·214 and 5·24 cm-1 for R = J and R ≠ J Coriolis sublevels respectively.
Abstract: Vibration-rotation intensities have been calculated for transitions between states of arbitrary vibrational symmetries, for tetrahedral molecules. For this purpose eigenfunctions of first order Coriolis interactions, which are assumed to be much smaller than anharmonic splittings, have been used. While some bands, among which fundamentals and overtones, follow the ΔR = 0 selection rule, for others the most intense vibration-rotation lines are those with ΔR maximum, in agreement with our double-resonance investigations of stretching levels of methane. One such investigation is presented here, in which the lower (3v3, F 2) level of CH4 has been found at 8906·78 cm-1, in close agreement with local-mode predictions. Several I.R. lines in this region have been assigned, the effective rotational constants being 5·214 and 5·24 cm-1 for R = J and R ≠ J Coriolis sublevels respectively.

20 citations


Journal ArticleDOI
TL;DR: The title compound of as discussed by the authors crystallizes in the orthorhombic space group P212121 with Z=4 and lattice parametersa=1744.2(4),b=1360.7(4,c=751.3(5) pm.
Abstract: The title compound crystallizes in the orthorhombic space group P212121 with Z=4 and lattice parametersa=1744.2(4),b=1360.7(4),c=751.3(5) pm. An x-ray analysis shows the compound to consist of discrete (h5-C5H5)2-Ti(Cl)NCMe+ cations and FeCl 4 − anions. The cation has a distorted tetrahedral structure (Ti-C: 231.9-237.6 pm; Ti-Z: 203 and 204pm; Ti-Cl: 230.4 pm; Ti-N: 213.5 pm; Z-Ti-Z: 133.2°; Cl-Ti-N: 91.7° (Z: centre of cyclopentadienyl ring). The relatively short Ti-Cl bond length indicates a modest Ti-Cl π-bonding contribution. The tetrachloroferrate(III) anion possesses a nearly undistorted tetrahedral geometry (Fe-Cl: 216.0–218.5 pm; Cl-Fe-Cl: 109.0–111.1°). Mossbauer and x-ray photoelectron spectroscopic data confirm the crystallographically derived structural features.

18 citations


Journal ArticleDOI
TL;DR: The structure of the unsaturated cluster compound [Os3Pt(µ-H)2(CO)10{P(cyclo-C6H11)3} with hydrogen and with diazomethane has been investigated by X-ray diffraction.
Abstract: Reactions of the unsaturated cluster compound [Os3Pt(µ-H)2(CO)10{P(cyclo-C6H11)3}] with hydrogen and with diazomethane have been investigated, and the structures of the products determined by X-ray diffraction. The structure of the previously prepared carbon monoxide adduct [Os3Pt(µ-H)2(CO)11{P(cyclo-C6H11)3}] has also been established. The latter species, which is formed in a readily reversed reaction, has a ‘butterfly’ arrangement of the metal atoms with the platinum atom at a wing-tip position. One hydrido-ligand bridges the Os–Os vector of the body of the butterfly, and the other an Os–Pt edge. The latter is cis to the P (cyclo-C6H11)3 group on the platinum, which also carries a CO ligand. The osmium atom at the other wing-tip is ligated by four CO groups, and the remaining two Os are each terminally bonded to three carbonyls. The hydrogen adduct [Os3Pt(µ-H)4(CO)10{P(cyclo-C6H11)3}] is also formed reversibly but in contrast with the product from carbon monoxide has a closo-tetrahedral metal core. The hydrido-ligands occupy edge-bridging sites on the cluster framework, with two bridging Os–Pt vectors [cis to the P(cyclo-C6H11)3 ligand on platinum] and two bridging Os–Os vectors. Thus the M4 tetrahedron has D2d symmetry with two short unbridged edges and four longer bridged edges. Diazomethane readily adds to [Os3Pt(µ-H)2(CO)10{P(cyclo-C6H11)3}] to give the complex [Os3Pt(µ-H)2(µ-CH2)-(CO)10{P(cyclo-C6H11)3}] which exists as an equilibrium mixture of two isomeric forms (orange-yellow and red crystals). Both species have a closo distorted tetrahedral geometry for the metal atoms, with the methylene group bridging an Os–Os edge cisoid to the P(cyclo-C6H11)3 ligand on the platinum in the orange-yellow form and transoid to the phosphine group in the red isomer. The relative positions of the hydrido-ligands also differ. In the orange-yellow form they bridge the remaining two Os–Os edges, while although not located directly in the red isomer, being assigned on potential-energy grounds, they bridge an Os–Os edge and the Os–Pt edge cis to the P(cyclo-C6H11)3 ligand. N.m.r. studies reveal that the two isomers maintain these solid-state structures in solution. The mechanism of formation of the two isomers is discussed in the context of the orange-yellow form being the kinetically controlled product, which after several days in solution establishes a 1 : 4 equilibrium with the red form.

17 citations


Journal ArticleDOI
TL;DR: In this article, the authors consider a tetrahedral molecule consisting of a central carbon atom attached to four different groups, A, B, G, and H, and prove that phase separation occurs at sufficiently low temperature and sufficiently high chemical potential for a certain range of intermolecular interactions.
Abstract: There are two nonsuperimposable mirror images (enantiomers) of a tetrahedral molecule consisting of a central carbon atom attached to four different groups, A, B, G, and H. We consider a lattice gas in which the two enantiomeric forms, d and l, are adsorbed onto a triangular lattice, such that the carbon atom is above a lattice site, the three bonds to A, B, and G are pointing toward neighboring lattice sites, and the bond to H points perpendicular to and away from the plane of the lattice. For a certain range of intermolecular interactions (such as may exist between the zwitterion forms of an amino acid) we prove, for a system which is equimolar in each enantiomer, that enantiomeric phase separation occurs at sufficiently low temperature and sufficiently high chemical potential. The phase diagram and critical point for the system are investigated using a first‐order Guggenheim approximation.

14 citations


Journal ArticleDOI
TL;DR: The crystal and molecular structure of the title metal complex of Co2Hg2(SCN)4 was determined by the X-ray diffraction method as discussed by the authors, and the crystal is triclinic, with the space group P\bar1, Z=1, a=11.934(2), b=14.642(9), c= 11.801(6)A, α=90.41(5), β=94.04(2)
Abstract: The crystal and molecular structure of the title metal complex was determined by the X-ray diffraction method. The crystal is triclinic, with the space group P\bar1, Z=1, a=11.934(2), b=14.642(9), c=11.801(6)A, α=90.41(5), β=94.04(2), and γ=83.82(2)°. The final R value for 6928 reflections is 0.065. The cobalt(II) ato is in a tetrahedral geometry, ligated by four nitrogen atoms of the thiocyanato (SCN) ligands, while the mercury(II) atom is in a trigonal-bipyramidal geometry, where two phosphorus atoms of both the triphenylphosphine ligands bond axially and three sulfur atoms of SCN’s equatorially; however, these Hg–S bonds are very long. Thus, the pairs of cobalt(II) and mercury(II) atoms are linked by one SCN bridge, forming a sixteen-membered ring of Co2Hg2(SCN)4, and this ring is linked with the next ones on both sides in the a-axis direction with two longer bondings.

10 citations


Journal ArticleDOI
TL;DR: The crystal and molecular structures of two dinuclear Co(II) compounds of formula [Co 2 I 4 (L) 2 ](C 6 H 6 ) n (L = PPh 3 or OPPh 3 ; n = 1,2) are described in this article.

7 citations


Journal ArticleDOI
TL;DR: In this article, a tetragonal planar polymeric complex was synthesized and its crystal and molecular structures were determined by the use of a single-crystal X-ray diffraction method.
Abstract: The new complex indicated in the title was synthesized and its crystal and molecular structures were determined by the use of a single-crystal X-ray diffraction method. The crystal is tetragonal, with the space group P\bar4, and the cell constants are a=12.124(5) and c=7.985(2) A. The structure was solved using the heavy-atom method, and the final R value was 0.039. Two kinds of crystallographically independent mercury atoms in the unit cell are tetra-coordinated and they are in the tetrahedral geometry, where four sulfur atoms of the thiocyanate ions are ligated, respectively. The cobalt atom is hexa-coordinated, and is in an octahedral geometry, where four nitrogen atoms of the thiocyanate ions are coordinated equatorially, and two water oxygen atoms axially. Thiocyanate ions span mercury and cobalt atoms to form two-dimensional networks parallel to the (001) plane. The planar polymeric complexes are linked to the c-axis direction, through hydrogen bonds between coordinated water molecules and N,N-dimet...

Journal ArticleDOI
TL;DR: In this article, arylidene-o-hydroxy derivative (L1) acts as a bivalent ONNO tetradentate ligand while the molecules of the other derivatives (L2-L5) are coordinated to the metal ions as bidentate NN ligands.
Abstract: Co(II), Ni(II) and Cu(II) complexes of some bifunctional arylidene-o-phenylenediamineSchiff bases have been prepared. Formation, stoichiometry and stability of the complexes have been tested in solution using electronic spectral measurements. Characterization of the complexes has been accomplished primarily by elemental analysis, molar conductance as well as electronic and IR spectral measurements. It is concluded that theo,o-hydroxy derivative (L1) acts as a bivalent ONNO tetradentate ligand while the molecules of the other derivatives (L2-L5) are coordinated to the metal ions as bidentate NN ligands. The Cu(II)-L1 complex is suggested to possess a tetrahedral geometry whereas the other complexes are suggested to exhibit a distarted octahedral geometry. The different bands observed in the electronic spectra of the complexes inDMF solutions have been assigned to the π-π*,L →M CT and d-d electronic transitions.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the frame distortion experienced by a non-polar polyatomic molecule colliding with thermal He was investigated by classical computation and concluded that in cases of practical importance the dipoles arising from frame distortion are probably comparable to those due to electronic overlap.


Book ChapterDOI
01 Jan 1985
TL;DR: In this paper, an interacting point atom polarizability model is introduced to calculate the collision induced pair polarizabilities of tetrahedral molecules, which is suitable for molecular dynamics simulations of condensed phases.
Abstract: Collision induced light scattering from tetrahedral molecules is an highly collective N-body process and depends — in principle — on the full charge distribution of the molecules and, consequently, on the full orientation dependent pair potentials and induced pair polarizabilities. The pair potential is usually treated in terms of many-center Lennard-Jones potentials. For the calculation of the collision induced pair polarizabilities an interacting point atom polarizability model is introduced, the properties of which are discussed. It may be cast into a form most suitable for molecular dynamics simulations of condensed phases. As an illustration of the applicability of these models a computer simulation for dense fluids resembling CF4 (for two different densities) and CCl4 are presented.

Journal ArticleDOI
TL;DR: In this paper, the formation of an enzyme-inhibitor adduct between bovine trypsin and [2- 13 C] p -amidinophenylpyruvic acid has been investigated by 13 C NMR spectroscopy.

Journal ArticleDOI
TL;DR: The crystal and molecular structure of diphenyladamant-1-ylmethylstannane, Sn(C6H5)2(C10H15)(CH3) has been determined by X-ray diffraction.

DOI
01 Aug 1985
TL;DR: In this article, it was shown that the ligand field strength in Bis(diphenyldithiophosphinato)iron(II) (2) is comparable to that in reduced rubredoxin (6250 cm−1) as determined from the diffuse reflectance spectrum.
Abstract: Bis(diphenyldithiophosphinato)iron(II) (2) is synthesised by the action of (C6H5)2PS2H on FeCO3. Spectroscopic data show that2 has got a distorted tetrahedral structure. The ligand field strength in2 (5748 cm−1) as determined from the diffuse reflectance spectrum is comparable to that in reduced rubredoxin (6250 cm−1). The isomer shift value in the Mossbauer spectrum of2 also is quite consistent with that reported for reduced rubredoxin and other iron(II) tetrahedral compounds. In solution and in the presence of air2 is spontaneously oxidised to the ferric complex [(C6H5)2PS2]3Fe (1). The dark green1 is reduced to the pale yellow ferrous complex2 by the action of NaBH4 inthf solution. This redox behaviour is comparable to that of rubredoxin, although the oxidised complex differs from oxidised rubredoxin in that it has got octahedral geometry compared to the tetrahedral geometry of the oxidised rubredoxin. The reaction of1 with 2,2′-bipyridyl, NH3, Br2 and NO and the Mossbauer spectra of the products are also described here.