Showing papers on "Tetrahedral molecular geometry published in 1996"
TL;DR: The molecular structure of a nickel(0) complex with P,S-donor atom ligands has been characterized by X-ray crystallography as discussed by the authors, and the results show that complex 3, (Ph2P(o-C6H4)SCH3)2Ni0, prepared by Na/Hg amalgam reduction of the NiII complex, degrades photochemically with loss of CH3 radicals to yield complex 3.
Abstract: The molecular structure of a nickel(0) complex with P,S-donor atom ligands has been characterized by X-ray crystallography. Complex 1, (Ph2P(o-C6H4)SCH3)2Ni0, prepared by Na/Hg amalgam reduction of the NiII complex [(Ph2P(o-C6H4)SCH3)2Ni](BF4)2 ([2](BF4)2), degrades photochemically with loss of CH3 radicals to yield complex 3, (Ph2P(o-C6H4)S)2NiII. Crystallographic parameters for the three compounds are as follows: 1, monoclinic space group C2/c with a = 11.467(2) A, b = 17.613(3) A, c = 15.733(2) A, β = 96.450(10)°, V = 3157.5(9) A3, and Z = 4; [2](BF4)2, monoclinic space group P21/c with a = 9.417(4) A, b = 14.822(9) A, c = 13.773(2) A, β = 98.55(3)°, V = 9101(14) A3, and Z = 2; and 3, monoclinic space group P21/c with a = 9.651(2) A, b = 12.971(8) A, c = 12.540(2) A, β = 110.46(2)°, V = 1470.7(11) A3, and Z = 2. While complex 1 has a distorted tetrahedral geometry, complexes [2](BF4)2 and 3 are square planar with trans stereochemistry. The cyclic voltammogram of [2](BF4)2 in CH3CN shows two redox even...
68 citations
TL;DR: In this article, two related sodium amide complexes derived from secondary amines with bulky organic substituents have been synthesised and crystallographically characterised, both of which adopt dimeric crystal structures with a central, planar (nitrogen-metal)(2) azametallocycle.
54 citations
TL;DR: The synthesis and structural characterization of water-soluble four-coordinate gold(I) complexes containing monodentate phosphine ligands are described and their ability to form a hydrogen-bonded network between the nitrogen atoms of the ligand and solvent water molecules is described.
Abstract: The synthesis and structural characterization of water-soluble four-coordinate gold(I) complexes containing monodentate phosphine ligands are described. The ligands used are 1,3,5-triaza-7-phosphaadamantane (TPA) and its protonated and methylated derivatives, [HTPA]Cl and [MeTPA]I. Formation of the four-coordinate gold(I) species is favored by the small cone angle of the phosphine (102°) and its ability to form a hydrogen-bonded network between the nitrogen atoms of the ligand and solvent water molecules. The gold center in all four complexes has a nearly regular tetrahedral geometry with an average P−Au−P angle of 109.5°. [(HTPA)3(TPA)Au](PF6)4·4H2O·CH3CN (1) crystallizes in the monoclinic space group P21/c (No. 14) with cell constants a = 20.719(3) A, b = 15.606(2) A, c = 17.854(2) A, β = 114.03(1)°, and Z = 4. Refinement of 4977 reflections and 650 parameters yields R = 0.0396 and Rw = 0.0500. [(TPA)4Au]PF6·1.5HCl·H2O (2), crystallizes in the monoclinic space group C2/c (No. 15) with cell constants a =...
49 citations
TL;DR: In this paper, the nido-diphosphine complexes with a trigonal planar or tetrahedral geometry have been synthesized and the structures of complexes 1, 3 and 5 have been established by X-ray crystallography.
Abstract: Silver complexes with the nido-diphosphine [7,8-(PPh2)2-7,8-C2B9H10]– have been synthesized. Reaction of [Ag(OClO3)(PR3)] with (PPh2)2C2B10H10 in refluxing ethanol affords the three-co-ordinate complexes [Ag{(PPh2)2C2B9H10}(PR3)](PR3= PPh31 or PPh2Me 2), whereas treatment of [Ag(OClO3){(PPh2)2C2B10H10}] with L–L under the same conditions leads to the formation of [Ag{(PPh2)2C2B9H10}(L–L)][L–L = 1,10-phenanthroline 3, bis(diphenylthiophosphoryl)methane 4 or 1,2-bis(diphenylphosphino)-1,2-dicarbadodecaborane(10)5]. The structures of complexes 1, 3 and 5 have been established by X-ray crystallography. The silver atoms show a trigonal planar (1) or tetrahedral geometry (3 and 5).
41 citations
TL;DR: An algebraic model of boson realization is proposed to study the vibrational spectra of a tetrahedral molecule, where ten sets of bosons creation and annihilation operators are used to construct the Hamiltonian with Td symmetry.
Abstract: An algebraic model of boson realization is proposed to study the vibrational spectra of a tetrahedral molecule, where ten sets of boson creation and annihilation operators are used to construct the Hamiltonian with Td symmetry. There are two schemes in our model. The first scheme provides an eight-parameter fit to the published experimental vibrational eigenvalues of methane with a root-mean-square deviation 11.61 cm(-1) The second scheme, where the bending oscillators are assumed to be harmonic and the interactions between the bending vibrations are neglected, provides a five-parameter fit with a root-mean-square deviation 12.42 cm(-1).
41 citations
TL;DR: In this paper, it was shown that one-electron oxidation of 1b leads to substantial lengthening of the Fe-P bonds and changes in the PFe-P and NFe-N angles.
Abstract: The complex [FeL2(NO)2](L = PEt31a, L = PPh31b or L2= dppe 1c) prepared from [{Fe(µ-I)(NO)2}2] and PPh3 or Ph2PCH2CH2PPh2(dppe){in the presence and absence of [Co(cp)2](cp =η5-C5H5) respectively} undergo one-electron oxidation at a platinum electrode in CH2Cl2. The complex [{Fe(µ-dppm)(NO)2}2]2, prepared from [{Fe(µ-I)(NO)2}2] and Ph2PCH2PPh2(dppm) in the presence of [Co(cp)2], undergoes two sequential one-electron oxidations. Complex 1b with [Fe(cp)2]+ gave 1b+, X-ray studies of which show a distorted tetrahedral geometry with near C2v symmetry. Oxidation of 1b leads to substantial lengthening of the Fe–P bonds and changes in the P–Fe–P and N–Fe–N angles. These changes are consistent with significant Fe–P π-bonding character in the singly occupied molecular orbital of 1b+. Cation 1b+ reacts with halide ions, giving [FeX(PPh3)(NO)2](X = Cl or I) and then [FeX2(NO)2]–, and with OPPh3 to give [Fe(OPPh3)(PPh3)(NO)2]+3. X-Ray studies on the last, as its [PF6]– salt, show a distorted tetrahedral geometry; the co-ordination angles at iron approach trigonal bipyramidal with the PPh3 ligand in one apical site and the other apical site vacant. The complex [Fe(OPPh3)2(NO)2]+4+ resulted from the reaction between [{Fe(µ-I)(NO)2}2] and OPPh3 in the presence of TlPF6. An analysis of the ESR spectra of the paramagnetic cations 1b+, 3+ and 4+, together with extended-Huckel MO calculations on models of 1b+ and 3+, suggest that the complex catalysts formed from [{Fe(µ-Cl)(NO)2}2] and Ag+ or Tl+ are also four-co-ordinate 17-electron radicals. A crystallographic database study of four-co-ordinate dinitrosyl complexes of iron and other metals confirms that the N–Fe–N and O ⋯ Fe ⋯ O angles are linearly related. Consideration of these geometric effects, and those resulting from oxidation of 1b, in the light of a model proposed by Summerville and Hoffmann provides insight into the bonding in these and related species.
34 citations
TL;DR: In this paper, a direct synthetic route, based on silver assisted metal exchange reaction, to cationic bis-ligand complexes of copper involving N-aryl-pyridine-2-aldimines (L, 1) has been studied.
30 citations
TL;DR: It is found that the persulfoxy sulfur becomes less sulfonium-ion-like in character with decreasing ring size, and it is speculated that the anticipated ring strain effect in the Persulfoxide is compensated for by a weaker sulfur-oxygen interaction and the corresponding relaxation of the need to attain the energetically preferred tetrahedral geometry.
Abstract: Ab initio methods are used to investigate ring strain effects on sulfide-singlet oxygen reaction intermediates. The optimized persulfoxide and thiadioxirane structures derived from 3-, 4-, and 5-membered ring sulfides showed minor albeit systematic changes in geometry. These persulfoxides and thiadioxiranes are best described as distorted tetrahedral and trigonal bipyramidal in nature, respectively. We find that the persulfoxy sulfur becomes less sulfonium-ion-like in character with decreasing ring size. In addition, the persulfoxide and the thiadioxirane are nearly isoenergetic in all cases and their interconversion barriers are nearly identical. We speculate that the anticipated ring strain effect in the persulfoxide is compensated for by a weaker sulfur-oxygen interaction and the corresponding relaxation of the need to attain the energetically preferred tetrahedral geometry.
20 citations
TL;DR: In this article, the copper linakge isomers of pyridine-2-cardaldehyde 2′-[yridylhydrazone (papyH)]ClO 4 and [Cu(PPh 3 ) 2 (E -papy H)]Cl O 4 have been prepared by the reaction of [Cu[PPh3 ] 2 (CH 3 CN) 2 ]ClO4 with the Z - and E -form of papyH.
19 citations
TL;DR: The algebraic approach proposed by Leroy and Michelot as discussed by the authors describes the vibrational stretching modes of polyatomic molecules for up to seven quanta and suggests a form of the dipole operator adapted to the ( n 000) local states by combining the strength of group theory method with the necessity of a compact formulation.
18 citations
TL;DR: In this article, a three-legged piano stool geometry is observed around ruthenium whereas the silicon adopts a distorted tetrahedral geometry, and the η1-Cp* group is σ-bound to the silicon and is static on the NMR time scale at room temperature.
TL;DR: In this article, a deformed harmonic oscillator was used to describe both the stretching and bending vibrational spectrum of a tetrahedral molecule, and the model provided a seven-parameter fit to the published experimental V2V spectrum of methane with a root-mean-square energy deviation 10.12 cm(-1).
TL;DR: The reaction of lanthanocenes Cp3Ln (Cp C5H5, Ln ǫ Dy, Yb) with the equimolar alcohols HOR [R] in THF forms three new dinuclear organolanthanide alkoxides, namely [Cp2Yb(μ-OCH2CH2 CH2CH 2CH2Ch2CH3, CH2 CH 2CH(Me)2] in this paper.
TL;DR: In this article, the title compounds, [Cu(C 6 H 7 NS) 4 ]BF 4 and [Ag-(C 6H 7 NS )BF 4, are both mononuclear complexes in which the central metal(I) cation (M I ) is surrounded by the four donor S atoms of the ligands.
Abstract: The title compounds, [Cu(C 6 H 7 NS) 4 ]BF 4 and [Ag-(C 6 H 7 NS) 4 ]BF 4 , are both mononuclear complexes in which the central metal(I) cation (M I ) is surrounded by the four donor S atoms of the ligands. The M I S 4 unit adopts a distorted tetrahedral geometry.
TL;DR: In this article, low-lying electronic states of Rh 4 with different geometries were considered using the complete active space multiconfiguration self consistent field method (CASSCF) followed by large scale multi-reference singles + doubles configuration interaction (MRSDCI) computations that included up to 2.1 million configurations.
TL;DR: In this article, Cp3Yb (Cp = C5H5) with equimolar n-propane thiol in THF at room temperature resulted in the formation of the new complex [Cp2Yb(μ-SCH2CH2 CH2CH3]2 in good yield, which was characterized by elemental analysis and mass spectra, and studies by X-ray crystallography.
TL;DR: A series of four-coordinate nickel(II) complexes have been prepared containing a tetradentate N2O2 aldimine or ketoimine Schiff-base ligand formed by condensation of 4-formyl-5-hydroxy- or 4-benzoyl-5hydroxypyrazoles with aliphatic diamines containing two or three carbon atoms (n= 2 or 3) as mentioned in this paper.
Abstract: A series of four-co-ordinate nickel(II) complexes have been prepared containing a tetradentate N2O2 aldimine or ketoimine Schiff-base ligand formed by condensation of 4-formyl-5-hydroxy- or 4-benzoyl-5-hydroxypyrazoles with aliphatic diamines containing two or three carbon atoms (n= 2 or 3). In non-donor solvents the low-spin (S= 0) state is favoured. The complexes with n= 2 are fully diamagnetic; the spin-equilibrium process (S= 0)⇌(S= 1) is, however, induced when n= 3. The crystal structure has been determined of {N,N′-bis[(5-hydroxy-1,3-diphenylpyrazolyl)phenylmethylene]propane-1,3-diaminato}nickel(II)1a which has a flattened tetrahedral geometry, and the spin-equilibrium process has been investigated for selected complexes by spectroscopic methods [ΔH 16–21 kJ mol–1, ΔS 2–22 J K–1 mol–1, and ΔG(50 °C) 14–19 kJ mol–1]. The four-co-ordinate complexes reversibly increase their co-ordination numbers in donor solvents (all) or by molecular association in non-donor solvents (the aldimine complexes only). Solid six-co-ordinate products from the reactions with dimethylsulfoxide (dmso), pyridine and water have been isolated, and the crystal structures determined of the product (1b) from the reaction of 1a with dmso and of that (3b) from the reaction of {N,N′-bis[(5-hydroxy-1,3-diphenylpyrazolyl)(p-tolyl)methylene]propane-1,3-diaminato}nickel(II) with dmso. Complexes 1b and 3b have trans distorted-octahedral geometries with O-bound dmso molecules in axial positions. The adduct formation with dmso [–ΔH 10–27 kJ mol–1, –ΔS 57–107 J K–1 mol–1, ΔG(25 °C) 0.9–7.0 kJ mol–1] and with pyridine [ΔG(25 °C)– 19 kJ mol–1] has been investigated for selected complexes by spectroscopic methods. Angular overlap model ligand-field parameters have been derived from the electronic absorption spectra.
TL;DR: The title compound C4H8N8S2HgBr2 was prepared and characterized by means of X-ray crystallography, and i.r. measurements as discussed by the authors, which exhibits discrete monometallic units with the 1,2,4-triazole molecule acting as a monodentate ligand.
Abstract: The title compound C4H8N8S2HgBr2 was prepared and characterized by means of X-ray crystallography, and i.r. measurements. The crystals are orthorhombic, space group Pbcn (no. 60) witha=9.707(2),b=8.609(1),c=16.128(2) A, andZ=4. The compound exhibits discrete monometallic units with the 1,2,4-triazole molecule acting as a monodentate ligand. The structure consists of units in which the mercury atom is coordinated in a distorted tetrahedral geometry by two sulfur and two bromine atoms. The NH and NH2 group of the 3-amino-5-mercapto-1,2,4-triazole unit are involved in intermolecular hydrogen bonds. Infrared bands are diagnostic of the coordination environment around the metal atoms.
TL;DR: In this article, the zinc complex [Zn(P(py)3)2]2]+ was determined to have octahedral geometry with six pyridine N donor atoms.
TL;DR: In this paper, a bis(ligand) complex of zinc(II) containing a Group 15 donor atom was identified by X-ray powder diffraction, which is known as ZnI2(AsMe3)2.
Abstract: The reaction of Et3AsI2 with zinc metal powder produced the dimeric complex [ZnI2(AsEt3)]2, whereas that of Me3AsI2 gave equimolar quantities of ZnI2(AsMe3)2 and ZnI2, the latter being identified by X-ray powder diffraction. Both arsine complexes have been structurally characterised and as such represent the only examples for zinc(II). A structural change is thus seen on changing the R groups on the R3AsI2 compound. The complex ZnI2(AsMe3)2 represents the sole example of a bis(ligand) complex of zinc(II) containing a Group 15 donor atom. Both complexes contain the zinc atoms in essentially tetrahedral geometry but significant distortion is noted for ZnI2(AsMe3)2, which may be the result of unfavourable steric interactions.
TL;DR: The monoclinic form of 1,4,8,11-tetraazacyclotetradecanecopper(II) tetrachlorocuprate, [Cu(14-ane)]CuCl4, has a chain structure consisting of Cu(14ane)2+ cations linked by CuCl42− anions as discussed by the authors.
Abstract: The monoclinic form of 1,4,8,11-tetraazacyclotetradecanecopper(II) tetrachlorocuprate, [Cu(14-ane)]CuCl4, has a chain structure consisting of Cu(14-ane)2+ cations linked by CuCl42− anions. The CuII ion has a square-planar coordination in the cation [average Cu-N distance = 2.020 (7) A] while the anion has a flattened tetrahedral geometry [average Cu-Cl distance = 2.246 (13) A with average trans Cl-Cu-Cl angles = 130 (1)°]. The cations and anions are linked by semi-coordinate Cu⋯Cl bonds with a distance of 2.855 (2) A to form chains which run parallel to the c axis and pack in a hexagonal array.
01 Feb 1996
TL;DR: The spectral density distribution of a Hamiltonian which represents a system of N coupled Morse oscillators and, hence, may approximately describe molecular vibrations in the local mode picture is analyzed in this article.
Abstract: The spectral density distribution of a Hamiltonian which represents a system of N coupled Morse oscillators and, hence, may approximately describe molecular vibrations in the local mode picture is analyzed. The spectral density moments are expressed as linear combination of products of coefficients which depend on the molecular structure and of one-particle moments describing individual bonds and interactions between them. Detailed expressions are analyzed for linear and tetrahedral molecules. Moreover a comparison with the case of coupled harmonic oscillators is given.
TL;DR: In this article, the authors measured and analyzed the temperature dependence of extended X-ray absorption fine structure (EXAFS) spectra of tetrahedral systems MBr 4 (M=C, Si, Ge).
Abstract: We have measured and analyzed the temperature dependence of extended X-ray absorption fine structure (EXAFS) spectra of tetrahedral systems MBr 4 ( M=C, Si, Ge). The EXAFS analysis by means of the cumulant expansion technique enables one to obtain information about force constants including the third-order anharmonicity. The second-order cumulants obtained experimentally are in excellent agreement with the values expected by the vibrational data and the third-order cumulants have been determined successfully. For the first nearest neighbor (NN) Br–M shells the stretching motions are apparently dominant to describe EXAFS, while for the second NN Br–Br shell the bending modes are found to contribute significantly to the cumulants especially for the third-order anharmonicity. The obtained force constants are compared to each other and the origin of observed bending anharmonicity is discussed.
TL;DR: The crystal structure of the title com pound has been determined by X-ray methods as discussed by the authors, where the lithium atom is coordinated in a distorted tetrahedral geometry by two THF molecules and by two chlorine atoms.
Abstract: The crystal structure of the title com pound has been determined by X-ray methods. Space group C2/c, Z = 4, lattice dimensions at -80 °C: a = 1343.8(2), b = 1031.6(1), c = 1669.4(1) pm, β = 96.47(1)°. The compound forms an ion pair in which the lithium atom is coordinated in a distorted tetrahedral geometry by two THF molecules and by two chlorine atoms. The halide atoms have a μ₂-bridging function, coordinating the lithium and the titanium center. The titanium atom possesses a distorted octahedral environment with two THF ligands in trans-position.
TL;DR: In this paper, the stoichiometry of the Co(II) Ni(II), Cu(II, and Zn(II)-complexes with the thiol form of methylisopropylketone and methylisobutyl-ketone thio-semicarbazones has been characterized by analytical, conductivity, magnetic moment, infrared, and ESR spectral studies.
Abstract: Bis-chelates of Co(II) Ni(II), Cu(II) and Zn(II) with the thiol form of methylisopropylketone and methylisobutylketone thio-semicarbazones have been synthesized and characterised by analytical, conductivity, magnetic moment, infrared, electronic and ESR spectral studies. Based on analytical data the stoichiometry of the complexes has been found to be 1:2. The conductivity data show that all the complexes are non-electrolytes. The Co(II) complexes were found to have polymeric octahedral geometry. The Ni(II) and Zn(II) complexes are diamagnetic and were found to have square-planar and tetrahedral geometry, respectively. Square-planar geometry has also been suggested for the paramagnetic Cu(II) complexes.
TL;DR: The crystal structure of bis(triphenylphosphine)iminium tetrakis ( pentafluorophenyl gallate, [N{P(C 6 H 5 ) 3 }2] [Ga[C 6 F 5 ) 4 ], has been determined by X-ray diffraction methods as discussed by the authors.
Abstract: The crystal structure of bis(triphenylphosphine)iminium tetrakis ( pentafluorophenyl gallate, [N{P(C 6 H 5 ) 3 }2] [Ga(C 6 F 5 ) 4 ], has been determined by X-ray diffraction methods. The tetrakis(pentafluorophenyl)gallate anion has almost tetrahedral geometry.
TL;DR: The title complex of as mentioned in this paper has two chelating Schiff base ligands coordinating through their N and O atoms to give a tetrahedral geometry distorted mainly by reduction of the chelate O-Co-N angles and by expansion of the N-Co -N angle because of steric hindrance of the isopropyl substituents.
Abstract: The title complex, bis[2-(2-propyliminomethyl)phenolato-N,O]cobalt(II), [Co(C 10 H 12 NO) 2 ], has two chelating Schiff base ligands coordinating through their N and O atoms to give a tetrahedral geometry distorted mainly by reduction of the chelate O-Co-N angles and by expansion of the N-Co-N angle because of steric hindrance of the isopropyl substituents. The Co-O bonds [mean 1.906(5) A] are shorter than the Co-N bonds [mean 1.992 (8) A].
TL;DR: In this paper, the Zn atom has been shown to exist in a slightly distorted tetrahedral geometry with two zwitterionic nicotinamide-N1-acetate substituents and two iodide ligands.
Abstract: In the title compound, [ZnI2(C8H8N2O3)2], the Zn atom, which lies on a twofold axis, exists in a slightly distorted tetrahedral geometry with two zwitterionic nicotinamide-N1-acetate substituents [Zn-O1 2.008 (2) A] and two iodide ligands [Zn-I 2.5848 (3) A]. Molecules of the complex are connected by intermolecular N-H⋯O hydrogen bonds, with N⋯O distances of 2.965 (3) and 3.133 (3) A.
TL;DR: In the case of meso-(3,5-di-tert-butylphenyl)methylenebis(2-pyrrole), C 23 H 30 N 2, the moieties surrounding the meso-C atoms formed a tetrahedral geometry.
Abstract: In molecules of the title compound, meso-(3,5-di-tert-butylphenyl)methylenebis(2-pyrrole), C 23 H 30 N 2 , the moieties surrounding the meso-C atoms form a tetrahedral geometry. There is no N-H...N hydrogen bonding present in the compound and molecules interact with each other through weak N-H...π interactions.
TL;DR: In this article, the title copper(I) complex of a substituted pyrimidyl hydrazone has been synthesized and characterized by X-ray diffraction, and the structure has been shown to contain one central Cu atom bonded to four N atoms in a tetrahedral geometry with two hydrazinic N atoms and two pyrimidine ring N atoms.