Showing papers on "Tetrahedral molecular geometry published in 1990"
TL;DR: In this article, the first stable organometallic derivative of the starting tetrahalide was synthesized with lithium-bis(trimethylsilyl)methyl in n-pentane and the crystal structure showed monomeric molecules with two trigonal planar coordinated metal atoms.
61 citations
TL;DR: In this paper, the crystal and molecular structures of 1a·DMF and 2a-DMF were determined from X-ray diffraction data and the compounds are isomorphous and crystallize in the triclinic space group P 1 with unit cell parameters for 1a(2a)-DMF: a=12.047(0) (12.053(2)), b= 17.620(3) (17.650(5)), c=14.514(1) (14.3)
40 citations
TL;DR: In this paper, it was shown that molecules with tetrahedral symmetry can give smectic liquid-crystalline phases, both with liquid and with ordered layers in contrast to the usual behaviour the layering is rather strong, leading to three orders in the X-ray diffraction pattern.
Abstract: It is shown that molecules with tetrahedral symmetry can give smectic liquid-crystalline phases, both with liquid and with ordered layers In contrast to the usual behaviour the layering is rather strong, leading to three orders in the X-ray diffraction pattern A tentative model is given in which the long mesogenic substituents are bent at the spacers with which they are attached to the central carbon atom, such that in spite of the tetrahedral angles a rod-like shape is obtained
33 citations
TL;DR: In this paper, the formation constants, enthalpies and entropies for chloro complexes of MnII, CoII, NiII and ZnII were determined and electronic spectra for the individual CoII and NiII complexes were extracted.
Abstract: The formation of chloro complexes of MnII, CoII, NiII and ZnII in dimethyl sulphoxide (DMSO) has been studied by calorimetry and spectrophotometry at 25°C. The formation constants, enthalpies and entropies for [MCln](2–n)+(n= 1–4; M = Mn, Co, Ni, Zn) were determined and electronic spectra for the individual CoII and NiII complexes were extracted. It is revealed that the coordination structure of [CoCl]+, [NiCl]+ and [NiCl2] is octahedral and that of [CoCl2], [CoCl3]–, [CoCl4]2–, [NiCl3]– and [NiCl4]2– is tetrahedral. Thus, an octahedral to tetrahedral geometry change occurs at the second step for CoII and at the third step for NiII. The log K1 values for the formation of [MCl]+ vary in the order Mn > Co > Ni Zn, which is different from the Irving–Williams series. The overall log β4 values follow the sequence Mn Ni < Cu < Zn. Complexation entropies of these metal systems are appreciably smaller in DMSO than in N,N-dimethylformamide (DMF), which is ascribed to stronger solvent–solvent interactions in DMSO.
32 citations
TL;DR: In this paper, the title compound, [Ag(dppe)2]NO3, is bis-chelated by two dppe ligands so that the silver atom is four-coordinate; Ag-P 2.527(3) A. The structure was refined by a full-matrix least squares procedure to final R = 0.063 for 3776 reflections with I ≥ 2.
Abstract: The title compound, [Ag(dppe)2]NO3, is shown to be bis-chelated by two dppe ligands so that the silver atom is four-coordinate; Ag-P 2.488(3), 2 × 2.523(3) and 2.527(3) A. Distortions from ideal tetrahedral geometry are related to the restricted bite distances of the dppe ligands such that the P(1)-Ag-P(2) and P(3)-Ag-P(4) angles are 84.5(1) and 83.8(1)°, respectively. The compound crystallizes in the monoclinic space group P21/n with unit cell dimensions a = 14.834(2), b = 19.795(2), c = 15.856(3) A, β = 93.09(1)° and Z = 4. The structure was refined by a full-matrix least-squares procedure to final R = 0.063 for 3776 reflections with I ≥ 2.5 σ(I).
32 citations
32 citations
TL;DR: In this paper, the structure factor of simple tetrahedral molecules X4 has been calculated as a function of ζ, where ζ is a ratio of the intermolecular atomic spacing L to the intramolecular atom spacing l, under constraints of a fixed preferred orientation between the nearest neighbors and a fixed packing fraction of uncorrelated molecules.
Abstract: Structure factor Sm(Q) of liquids of simple tetrahedral molecules X4 has been calculated as a function of ζ, where ζ is a ratio of the intermolecular atomic spacing L to the intramolecular atomic spacing l, i.e., ζ=L/l, under constraints of a fixed preferred orientation between the nearest neighbors and a fixed packing fraction of uncorrelated molecules. It turned out that the Sm(Q) depends strongly on the ratio ζ. An important feature of the calculated Sm(Q)’s is an appearance of a new peak at low Q region and its rapid growth with increasing ζ. The characteristic features of the experimental Sm(Q)’s of liquids P4 and VCl4 can be reasonably reproduced by the present simple calculation with ζ=1.64 for liquid P4 and 1.14 for liquid VCl4. These values of ζ are simply interpreted by the molecular size and intramolecular atomic spacing of each molecule.
30 citations
TL;DR: In this paper, the interaction of lithium alkyls in diethyl ether in the presence of tetramethylethylenediamine (TMED, Me2NCH2CH2NMe2) with cobalt(II) chloride has led to the isolation of four complexes whose crystal structures have been determined.
27 citations
TL;DR: In this paper, the authors investigated the integrated intensity IVH of the depolarized light scattering of liquids and liquid mixtures composed of tetrahedral molecules and found that the major contribution to IVH arises from dipole induced dipole interactions, and the marked decreases of (IVH/ρ2) with small changes of density ρ is attributed to significant increases in the symmetry of the local molecular environment of a given molecule.
Abstract: We have investigated, both experimentally and theoretically and as a function of both temperature and pressure, the integrated intensity IVH of the depolarized light scattering of liquids and liquid mixtures composed of tetrahedral molecules. The major contribution to IVH arises from dipole‐induced–dipole interactions, and the marked decreases of (IVH/ρ2) with small changes of density ρ is attributed to significant increases in the symmetry of the local molecular environment of a given molecule, perhaps an increase associated with ‘‘interlocking structures’’ or ‘‘meshing of gears.’’ We believe IVH/ρ2, because of its sensitivity to the placement of all near neighbors of a molecule, may be a useful probe of local structure, particularly for tetrahedral molecules.
24 citations
TL;DR: In this article, the results of the reaction of the diphosphine ligand with the symmetric diphphosphine Ph2P(S)CH2CH2PS)PPh2 led to the formation of a seven-membered ring, a result which is unprecedented in phosphine/arsine chalcogenide chemistry.
Abstract: Reaction of mercury(II) iodide with the unsymmetrical diphosphine ligand Ph2P(S)CH2PPh2 resulted in the formation of a solid compound [HgI2{Ph2P(S)CH2PPh2}] (1), which has been shown by X-ray crystallography to be monomeric with a flattened tetrahedral geometry about the mercury atom. The diphosphine co-ordinates via the sulphur and trivalent phosphorus atoms [Hg–S(1) 2.760(4), Hg–P(2) 2.503(5) A] forming a five-membered ring; the two remaining tetrahedral sites are occupied by the iodide atoms [Hg–I 2.727(2) and 2.693(2) A]. Crystals of (1) are monoclinic, space group P21/c, with unit-cell dimensions a = 11.426(2), b = 15.491(4), c = 16.324(3) A, β = 109.79(1), and Z = 4. The structure was refined to final R = 0.059 for 2 632 reflections with I 3.0σ(I). The reaction of mercury(II) chloride with the symmetrical diphosphine Ph2P(S)CH2CH2(S)PPh2 led to the isolation of the adduct [HgCl2{Ph2P(S)CH2CH2(S)PPh2}] (2). Crystallographic studies revealed a distorted tetrahedral mercury centre defined by two chloride atoms [Hg–Cl 2.447(3) and 2.442(3) A] and a chelating diphosphine ligand which co-ordinates via the sulphur atoms [Hg–S(1) 2.559(3) and Hg–S(2) 2.546(3) A]. The mode of co-ordination of the diphosphine ligand results in the formation of a seven-membered ring, a result which is unprecedented in phosphine/arsine chalcogenide chemistry. Crystals of (2) are monoclinic, space group P21/n, with unit-cell dimensions a = 8.404(4), b = 16.829(3), c = 19.354(3) A, β = 91.02(3), and Z = 4. The structure was refined to final R = 0.056 for 3 406 reflections with I 2.5σ(I).
23 citations
TL;DR: In this paper, single-crystal X-ray structure analyses were performed for these complexes: (1)·MeCN, triclinic, space group P, a= 17.402(3), b= 19.353(4), c= 9.774(4)A, α= 99.59(3).
Abstract: The salts [PPh4]2[Zn(C3Se5)2](1) and [PPh4]2[Zn(CSe4)2](2) were isolated from a solution of carbon diselenide with sodium metal in the presence of zinc(II) chloride and [PPh4]Br in dimethyl sulphoxide or in MeOCH2CH2OCH2CH2OMe. Single-crystal X-ray structure analyses were performed for these complexes: (1)·MeCN, triclinic, space group P, a= 17.402(3), b= 19.353(4), c= 9.774(4)A, α= 99.59(3), β= 98.37(3), γ= 65.51(2)°, and Z= 2; (2) monoclinic, space group P21/n, a= 21.586(2), b= 24.136(2), c= 10.208 4(7)A, β= 104.87(7)°, and Z= 4. The structure refinements converged to R= 0.060 and 0.072 for (1) and (2), respectively. Both complexes assume a tetrahedral geometry around the metal atom, the ligands being almost planar. Electronic absorption and 77Se n.m.r. spectra of the complexes were measured.
TL;DR: In this article, the ambiguities of the effective Hamiltonians for isolated doubly excited vibrational states of tetrahedral molecules are investigated theoretically, and reduced forms of these Hamiltonians and invariant parameters are proposed.
Abstract: The ambiguities of the effective Hamiltonians for isolated doubly excited vibrational states of bending modes of tetrahedral molecules are investigated theoretically. Reduced forms of these Hamiltonians and invariant parameters are proposed. The theoretical conclusions are tested by actual fits of experimental data for the 2v 2, vIn2 + v 4 and 2v 4 bands of 12CH4. The experimental behaviours of fitted parameters are found to be in satisfactory agreement with theory. The results obtained, which represent one step of the comprehensive study of the so-called pentad, lead to significant improvements not only in the convergence of least squares but also in the accurate understanding of the physical meaning of specroscopic parameters. A generalization to states including n quanta of the v 1 mode is outlined.
TL;DR: In this article, a neutron diffraction study of the atomic structure of deuterated molten ammonium nitrate (N(1)D4N(2)O3) was carried out at 453 K. The results of the total and first order differences demonstrate the existence of stable ND+ 4 and NO- 3 ions in the melt.
Abstract: A neutron diffraction study of the atomic structure of deuterated molten ammonium nitrate (N(1)D4N(2)O3) was carried out at 453 K. The first and second order isotopic difference methods of neutron diffraction were applied to the nitrogen nuclei of the ammonium and nitrate ions. The results of the total and the first order differences demonstrate the existence of stable ND+ 4 and NO- 3 ions in the melt. The ND+ 4 ions conform to a tetrahedral geometry and the NO- 3 ions retain a D 3h symmetry arising from a triangular geometry. The second order difference enabled the determination of the ‘cross’ pair distribution function g N(1)N(2)(r), from which it was concluded that the crystal structure relaxes significantly on melting.
TL;DR: In this paper, an X-ray crystal structure determination of the complex Mn(CH3-η5-C5H4) with a one molar proportion of iodine yields MnI2(OPPh3)2 as the only isolateable product.
TL;DR: In this paper, it is inferred that the tetrahedral molecule receives not only the octahedral field at one site but also the tetric field at the other site from hcp structure in host atoms.
Abstract: M. Prager et al . have shown by inelastic neutron scattering that the methane molecules dispersed in solid argon have two sites. It is inferred that the tetrahedral molecule receives not only the octahedral field at one site but the tetrahedral field at the other site. The latter field may be contributed from hcp structure in host atoms. The crystal field analysis is made in 3rd, 4th, and 6th orders using the conventional atom-atom potentials. It is concluded that C 3v configuration is dominant in fcc lattice while T d one in hcp lattice. In addition, rotational energy levels are computed in terms of the estimated field parameters. The result is compatible with the observed neutron scattering spectra.
TL;DR: In this article, a set of relationships among the force constants in dependent simple rectilinear internal valence coordinates for XY 4 tetrahedral, XY 6 octahedral and XY 5 trigonal-bipyramidal molecules resulting from their pure vibrational force fields is reported.
TL;DR: The incoherent inelastic neutron scattering spectrum of the defect pyrochlore, NH4TaWO6, has been determined at 20 K as discussed by the authors, which indicates that the NH4+ion is distorted from its free ion tetrahedral geometry.
Abstract: The incoherent inelastic neutron scattering spectrum of the defect pyrochlore, NH4TaWO6, has been determined at 20 K. The appearance of the spectrum indicates that the NH4+ion is distorted from its free ion tetrahedral geometry. A profile refinement method has been used to fit a calculated spectrum to the data based on an ion of C3v symmetry.
TL;DR: In this paper, the ZFS part of a spin Hamiltonian is expressed in terms of the distortion along normal coordinates and the coefficients characteristic of a metal-ligand combination, which is particularly useful in the calculation of ZFS under non-axial distortions.
Abstract: A systematic approach is developed for the ZFS (zero-field splitting) parameters D and E in slightly distorted tetrahedral and octahedral complexes with spatially non-degenerate ground states. This approach is illustrated by treatment of the normal coordinate system. The ZFS part of a spin Hamiltonian is expressed in terms of the distortion along normal coordinates and the coefficients characteristic of a metal-ligand combination. This expression for a spin Hamiltonian clarifies the relation between the ZFS and the distortions of the coordination geometry from Td and Oh symmetries, and is particularly useful in the calculation of the ZFS under non-axial distortions. Some of the coefficients are derived for the ground A2 state (tetrahedral d7 and octahedral d3) ions in terms of the e σ and e π parameters of the angular overlap model. Satisfactory agreement is obtained in the application of the approach to Cs3CoCl5, Cs2CoCl4 and ruby.
TL;DR: In this paper, the central C atom exists in a slightly distorted tetrahedral geometry, and the dihedral angles between the three pyridyl rings are 103.6, 106.8 and 88.4°, respectively.
Abstract: C₁₆H₁₃N₃, M(r)=247.3, monoclinic C2/c, a = 13.998(1), b = 8.653(1), c = 22.368(2) A, β = 103.15(1)°, U = 2638(1)A³, D(x) = 1.245 Mgm⁻³, Z = 8, Mo Kα radiation, λ = 0.7107 A, μ = 0.042 mm⁻¹, F(000) = 1040, T = 293(2)K, R = 0.034 for 947 observed reflections. In the title compound, (2-py)₃CH, the central C atom exists in a slightly distorted tetrahedral geometry [tetrahedral angles range from 105(1) to 113.8(2)°]. The C-C(py) distances are 1.517(4), 1.515(4) and 1.522(4) A and the dihedral angles between the three pyridyl rings are 103.6, 106.8 and 88.4°, respectively. One of the pyridyl rings is disordered with a 180° rotation about the C(methane)-C(py) bond at C(1)-C(31). In the major conformation (ca 58%) the two N atoms are orientated as to point in the same direction as the methane H atom.
TL;DR: In this article, the ester enolate anion CH2C(OEt)O− reacts with acetaldehyde and with acetone in the gas phase to produce stable adducts that are amenable to study by collisional activation and tandem mass spectrometry (MS/MS).
Abstract: The ester enolate anion CH2C(OEt)O– reacts with acetaldehyde and with acetone in the gas phase to produce ‘stable’ adducts that are amenable to study by collisional activation and tandem mass spectrometry (MS/MS). The activated adducts and deprotonated β-hydroxy ethyl ester reference ions both decompose by elimination of H2O, Et˙, H2O followed by EtOH, and by a retro reaction to reform CH2C(OEt)O–. The losses of H2O, Et˙, and EtOH are assigned to be characteristic of a species of tetrahedral geometry. These losses are, however, attenuated for the ion–molecule adducts because, in addition to existing as tetrahedral complexes, they are also formed as ion–dipole and proton-bound species.
TL;DR: In this paper, the bis-complexes of the form [ML 2 ]X 2 · n H 2 O (where M Zn II or Cd II, L = diethylenetriamine, and n = 1 when XCP − or Br −, n = 3 when X = 0.5SO 2−4 or 0.6SO 2 − 4 or 1.5SeO 2− 4, n = 0 when X= NO − 3 or SCN − ) have been synthesized, characterized and
TL;DR: In this article, a series of metal complexes with three tetradentate Schiff bases derived from benzoin and benzil withc-toluidine and benzin with diaminoethane have been prepared and characterised by physical and chemical methods.
Abstract: A series of metal complexes with three new tetradentate Schiff bases derived from benzoin and benzil withc-toluidine and benzil with diaminoethane have been prepared and characterised by physical and chemical methods. The modes of bonding of the ligands with the metal ions have been proposed. Electronic spectra and room temperature magnetic moment values suggest octahedral geometry for the CoII and NiII complexes, whereas the HgII and CdII complexes have tetrahedral geometry. The CuII complexes are square planar. Apart from the complexes of the Schiff bases derived from benzoin, all the other complexes have high molar conductance values suggesting them to be electrolytes. The complexes have been screened against some fungal pathogens.
TL;DR: In the title compound osmium(VI) has unusual distorted tetrahedral geometry, with two oxo and two S-bonded thiosulphato ligands; Raman, IR and 17O NMR spectra show that this structure is maintained in solution as discussed by the authors.
Abstract: In the title compound osmium(VI) has unusual distorted tetrahedral geometry, with two oxo and two S-bonded thiosulphato ligands; Raman, IR and 17O NMR spectra show that this structure is maintained in solution.
TL;DR: The three potential chelating ligands dihydridobis-, hydridotris- and tetrakis-(thiophenolyl)borate anions, and their chelates with first row transition metals have been synthesized.
Abstract: The three new potential chelating ligands dihydridobis-, hydridotris- and tetrakis-(thiophenolyl)borate anions, and their chelates with first row transition metals have been synthesised. The divalent and trivalent metal ions form complexes in 1∶2 and 1∶3 (metal:ligand) ratios respectively. The number of ligands coordinated correspond to the number of anions replaced in the metal salis. The compounds were characterized by elemental analysis, i.r. spectra, magnetic susceptibility measurements and electronic spectral studies. The CrIII and FeIII complexes of dihydridobis- and hydridotris-(thiophenolyl)borates appear to be octahedral, and those of CuII are proposed to be square planar. Tetrahedral geometry is suggested for the MnII, CoII and NiII complexes. The tetrakis-(thiophenolyl)borate yielded octahedral complexes with all the metal ions except for CuII which is square planar. The ligand field parameters 10Dq, B and β have also been calculated wherever possible. The ligands may be placed in the vicinity of EDTA in the nephelauxetic series.
TL;DR: In this paper, the permutation symmetry groups introduced by Longuet-Higgins are employed to solve the group theory for molecules of C3v and Td symmetry rotating in crystal fields of C 3v and td symmetry.
Abstract: The permutation symmetry groups introduced by Longuet-Higgins are employed to solve the group theory for molecules of C3v and Td symmetry rotating in crystal fields of C3v and Td symmetry. The qualitative appearances of the energy level diagrams for the groups (C3v, [Cbar]3v), (C3v, [Tbar]d) and (Td, [Cbar]3v) are deduced for the range of barrier heights from the free-rotor limits to the pinned limits, for the ground state multiplet only. The correlations between the groups derived here and the group (Td, [Tbar]d) treated by Miller and Decius are considered and the alteration in the ground state splitting pattern in going from a tetrahedral molecule in a tetrahedral field through to a trigonal molecule in a trigonal field is illustrated. The group (C3v, [Cbar]3v) is treated in detail and applied to the tunnelling states of monodeuteromethane adsorbed on the surface of graphite. The rotational Hamiltonian matrix is constructed in the pocket state formalism and diagonalized using the character table for (C3...
TL;DR: In this paper, the ester enolate anion CH2C(OEt)O− reacts with acetaldehyde and with acetone in the gas phase to produce stable adducts that are amenable to study by collisional activation and tandem mass spectrometry (MS/MS).
Abstract: The ester enolate anion CH2C(OEt)O– reacts with acetaldehyde and with acetone in the gas phase to produce ‘stable’ adducts that are amenable to study by collisional activation and tandem mass spectrometry (MS/MS). The activated adducts and deprotonated β-hydroxy ethyl ester reference ions both decompose by elimination of H2O, Et˙, H2O followed by EtOH, and by a retro reaction to reform CH2C(OEt)O–. The losses of H2O, Et˙, and EtOH are assigned to be characteristic of a species of tetrahedral geometry. These losses are, however, attenuated for the ion–molecule adducts because, in addition to existing as tetrahedral complexes, they are also formed as ion–dipole and proton-bound species.
TL;DR: In this article, it is suggested that other ambident species may also react with Me3B to form several tetrahedral species, e.g. deprotonated methyl acetate.
Abstract: Nucleophilic addition of CD3O– to Me2BOMe gives the same addition product as the corresponding reaction between Me2BOCD3 and MeO–, as evidenced by the identical collisional activation mass spectra of the products. This is interpreted in terms of exclusive formation of a boron product ion of tetrahedral geometry. The decompositions of the product involve loss of MeOH and CD3OH and the formation of MeO– and CD3O–. The major decompositions of (CD3)3B +–OCH2CH2XMe (X = O, S, or NMe2) are similar to those outlined above and may be explained by initial formation of (CD3)3 OCH2CH2XMe. However, there are some unusual fragmentations (e.g. loss of CH3D) which may occur through the alternative structure (CD3)3[graphic omitted](Me)CH2CH2O–. It is suggested that other ambident species may also react with Me3B to form several tetrahedral species, e.g. deprotonated methyl acetate could yield Me3CH2CO2Me, Me3OC(OMe)CH2, and Me3—[graphic omitted](Me)[graphic omitted]. The formation of the third structure is supported by the pronounced loss of ketene from this system.
TL;DR: In this article, the interaction of lithium alkyls in diethyl ether in the presence of tetramethylethylenediamine (TMED, Me2NCH2CH2NMe2) with cobalt(II) chloride has led to the isolation of four complexes whose crystal structures have been determined.
Abstract: The interaction of lithium alkyls in diethyl ether in the presence of tetramethylethylenediamine (TMED, Me2NCH2CH2NMe2) with cobalt(II) chloride has led to the isolation of four complexes whose crystal structures have been determined. The complexes (TMED)CoR2, R = CH2SiMe3 and CH2CMe3, have tetrahedral geometry about cobalt; in [(TMED)Li]2[Co(CH2SiMe3)4] there are CH2SiMe3 groups bridging the lithium and cobalt atoms; in the ionic complex [(TMED)2Li][CoCl{CH(SiMe3)2}2] the geometry about cobalt is trigonal planar. Electron paramagnetic resonance spectra of the complexes and of the products of the reaction with oxygen are reported.
TL;DR: In this article, the central C atom exists in a slightly distorted tetrahedral geometry, and the dihedral angles between the three pyridyl rings are 103.6, 106.8 and 88.4°, respectively.
Abstract: C₁₆H₁₃N₃, M(r)=247.3, monoclinic C2/c, a = 13.998(1), b = 8.653(1), c = 22.368(2) A, β = 103.15(1)°, U = 2638(1)A³, D(x) = 1.245 Mgm⁻³, Z = 8, Mo Kα radiation, λ = 0.7107 A, μ = 0.042 mm⁻¹, F(000) = 1040, T = 293(2)K, R = 0.034 for 947 observed reflections. In the title compound, (2-py)₃CH, the central C atom exists in a slightly distorted tetrahedral geometry [tetrahedral angles range from 105(1) to 113.8(2)°]. The C-C(py) distances are 1.517(4), 1.515(4) and 1.522(4) A and the dihedral angles between the three pyridyl rings are 103.6, 106.8 and 88.4°, respectively. One of the pyridyl rings is disordered with a 180° rotation about the C(methane)-C(py) bond at C(1)-C(31). In the major conformation (ca 58%) the two N atoms are orientated as to point in the same direction as the methane H atom.