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The novel vanadium thiobromide, V(sub 4)S(sub 9)Br(sub 4), with a square-planner metal cluster core was synthesized and characterized by single-crystal X-ray diffraction, measurements of magnetic property and the heat capacity, and density functional theory (DFT) calculation of the electronic structure. The electronic structure of V(sub 4)S(sub 9)Br(sub 4) is characterized by a high spin state, that is, the electronic system is in the excited state.

Single crystals of Ta4S9Br8 are obtained by heating Ta, S, and Br2 and the structure is determined by X-ray analysis consisting of molecular clusters [Ta4(mu4-S)(mu-S2)4Br8]. The compound is soluble in CH3CN, giving a dark-red solution with a characteristic electronic spectrum, which is assigned on the basis of DFT calculations.

The article discusses the synthesis and the characterization of an organometallic trinuclear niobium cluster complex in aqueous solution. The significance of the presence of the [Nb.sub.3]([mu]-[n.sup.2]:[n.sup.2]-NCC[H.sub.3])[([mu.sub.2]-O).sub.3.sup.6)] cluster core in such complexes is also demonstrated.

The mobility of aromatic chiral molecules 1-phenylethanol and 1-phenyl-1-propanol in liquids was studied by ¹H NMR spectroscopy depending on the strength of the external magnetic field, temperature, and concentration ratio of enantiomers. The data obtained were analyzed using Arrhenius law. The activation parameters were found to depend on the applied field. This effect is caused by the induced magnetic moments in aromatic molecules. The use of strong magnetic fields seems to be promising for investigation of intermolecular interactions of chiral molecules. [ABSTRACT FROM AUTHOR]

Molecular diamagnetism and multicentered X–Mo–Moand Mo–Mo–Mo interactions in hexanuclear cluster complexes[Mo6X8]n-(X = S, Se, and Te; n= 0 and 4) are studied usingcalculations of nuclear independent chemical shifts (NICS) and themethods “atoms in molecules” and electron localizationfunction. It is shown that [Mo6X8]4-complexes are characterized by large negative NICSs related to thearomaticity of Mo–Mo bondings and to diatropic currents inMo6metallic core of the cuboctahedral clusters. The calculated currents can participate in the mechanism of nucleation of the vortexlattice of macroscopic Abrikosov’s electronic whirls responsiblefor the magnetic high-field stability of the superconductingcurrents in type II superconductors. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of an organometallic It/nuclear oxo-bridged niobium cluster complex with perpendicularly coordinated μ3-η2:η2(⊥)-acetonitdle ligand in aqueous solution is reported. Reaction of NbCl5 in acelonitrile with aluminum under argon followed by reaction with aqueous hydrochloric acid affords, after suitable workup, the isolation of the organometallic [Nb3(μ-η2:η2-NCCH3)O3(H2O)9]6+ aqua ion by cation-exchange chromatography. The purple niobium aqua ion in 2 M HCI shows a small peak at 365 nm (ϵ ∼ 511 M-1 cm-1 per Nb) and a broad peak at 565 nm (ϵ ∼335 M-1 cm-1) in the UV-visible region. It is electron paramagnetic resonance (EPR)-active (g = 1.98), but no hyperfine interaction with the 93Nb nuclear spin (l= 9/2) was observed. The cyclic voltammogram of [Nb3(μ-η2:η2-NCCH3)O3(H2O)9]6+ in 4 M HCI on edge-plane pyrolytic graphite electrode at 50 mV s in the potential range -1.2 V to +1.1 V (vs SCE) exhibits three anodic peaks at -0.12, +0.53, and +0.85 V and a large cathodic peak at -0.91 V with a slight shoulder at about -0.8 V. The purple aqua ion reacted with potassium thiocyanale to give the green thiocyanate derivative, which was crystallized as ((CH3)3NH)3[Nb3(μ-η2:η2-NCCH3)O3(NCS)9]-2.5H2O (1) and subjected to X-ray structure analysis. Density-functional theory (DFT) calculations fully supported the structure of the cluster. [ABSTRACT FROM AUTHOR]

Reactions of rhenium chalcobromides Cs4[{Re6(μ3-S)8}Br6]·2H2O, Cs3[{Re6(μ3-Se)8}Br6]·2H2O, Cs3[{Re6(μ3-Q)7(μ3-Br)}Br6]·H2O (Q = S, Se), and K2[{Re6(μ3-S)6(μ3-Br)2Br6] with molten triphenylphosphine (PPh3) have resulted in a family of novel molecular hybrid inorganic-organic cluster compounds. Six octahedral rhenium cluster complexes containing PPh3 ligands with general formula [{Re6(μ3-Q)8-n(μ3-Br)n}(PPh3)4-nBrn+2] (Q = S, n = 0, 1, 2; Q = Se, n = 0, 1) have been synthesized and characterized by X-ray single-crystal diffraction and elemental analyses, 31P{¹H} NMR, luminescent measurements, and quantum-chemical calculations. It was found that the number of terminal PPh3 ligands in the complexes is controlled by the composition and consequently by the charge of the cluster core {Re6Q8-nBrn}n+2. In crystal structures of the complexes with mixed chalcogen/bromine ligands in the cluster core all positions of a cube [Q8-nBrn] are ordered and occupied exclusively by Q or Br atoms. Luminescence characteristics of the compounds trans-[{Re6Q8}(PPh3)4Br2] and fac-[{Re6Se7Br}(PPh3)3Br3] (Q = S, Se) have been investigated in CH2Cl2 solution and the broad emission spectra in the range of 600–850 nm were observed. [ABSTRACT FROM AUTHOR]

By treatment of Zn-reduced ethanolic solutions of NbCl5 with HCI in the presence of sulfide followed by cation-exchange chromatography, two oxo-sulfido niobium aqua ions, the red [Nb4(μ4-S)(μ2-O)5(H2O)10]4+ and the yellow-brown [Nb5(μ3-S)2(μ3-O)2(μ2-O)2(H2O)14]8+, were isolated. Both readily form their respective thiocyanate complexes, for which the structure for the former has been previously reported. Brown crystals of (Me2NH2)6[Nb5S2O4(NCS)14]. 3.5H2O (1) were isolated in the case of the latter, and the structure was determined by X-ray crystallography (space group: a = 15.4018(5) Å, b = 21.1932(8) Å, c = 22.0487(8) Å, α = γ = 90°, β = 103.4590(10)°, and R1 = 0.0659). An unprecedented pentanuclear Nb5S2O48+ core is revealed in which short Nb-Nb distances (2.7995- (8)-2.9111(8) Å) are consistent with metal-metal bonding. A stopped-flow kinetic study of the 1:1 equilibration of NCS- with [Nb4(μ4-S)(μ2-O)5(H2O)10]4+ has been carried out. Equilibration rate constants are independent of [H+] in the range investigated (0.5–2.0 M) and at 25 °C; k1 = 9.5 M-1 s-1, kaq = 2.6 × 10-2 s-1, and K = 365 M-1. Conditions with first NCS- and then [Nb4(μ4-S)(μ2-O)2(H2O)10]4+ in excess revealed a statistical factor of 4, suggesting the presence of four kinetically equivalent Nb atoms. Attempts to study the 1:1 substitution of NCS- with [Nb5- (μ3-S)2(μ3-O)2(μ2-O)2(H2O)14]8+ showed signs of saturation kinetics. Quantum chemical calculations using the density functional theory (DFT) approach were performed on both the Nb4O5S4+ and Nb5O4S28+ naked clusters. The highest occupied and lowest unoccupied molecular orbitals have dominant Nb(4d) character. The HOMO for Nb4O5S4+ is a nondegenerate fully filled MO, whereas for Nb5O4S28+, it is a nondegenerate partially filled MO with one unpaired electron. EPR spectroscopy on [Nb5(μ3-S)2(μ3-O)2(μ2-O)2(H2O)14]8+ shows that the molecule has total anisotropy (C2v), with all three tensors, gx = 2.399, gy = 1.975, and gz = 1.531, resolved. No hyperfine interaction expected from the nuclear moment of I = 9/2 for 93Nb was observed. [ABSTRACT FROM AUTHOR]

A reaction between ReI 3 and KCN at elevated temperature led to the formation of the new cyanometalate cluster anion [{Re 4 (μ 3 -CCN) 4 }(CN) 12 ] 8- ( 1 ). The anion contains μ 3 -CCN 3- ligands, which are stabilized by the coordination to the triangular faces of the tetrahedral {Re 4 } metallocluster in a μ 3 mode. The compound crystallized as a potassium salt, and its crystal structure was determined by single-crystal X-ray diffraction analysis. It was shown that μ 3 -CCN 3- ligands are ambidentate and can interact with transition-metal cations similarly to terminal CN groups, resulting in the polymer framework formation.

New tetrahedral anionic rhenium cluster complexes [{Re 4 (PO) 3 (PO 2 )}(CN) 12 ] 8- (1) and [{Re 4 As 2 (AsO) 2 }(CN) 12 ] 8- (2) have been synthesized by the reaction of ReI 3 with NaCN and P red or KCN and As gray , respectively. Compound 2 was further oxidized by aqueous H 2 O 2 to produce the cluster anion [{Re 4 (AsO) 4 }(CN) 12 ] 8- (3). The anions contain new pnictogen/oxygen-based ligands, PO 2 3- and AsO 3- , which were stabilized by the coordination to the triangular faces of the tetrahedral Re 4 metallocluster in μ 3 -mode. All three compounds were crystallized as either sodium or potassium salts, and their crystal structures were determined by single crystal X-ray diffraction analysis.

Selective substitution of μ-SO 2 2- groups by either O 2- or Se 2- ions occurs upon heating the bioctahedral rhenium cluster complex K 6 [Re 12 CS 14 (μ-SO 2 ) 3 (CN) 6 ] in air atmosphere or in the presence of a Se source, respectively, manifesting the remarkable lability of SO 2 2- ligands bound to a transition-metal cluster. A series of compounds based on the new mixed-ligand anions, [Re 12 CS 14 (μ-O) 3 (CN) 6 ] 6- , [Re 12 CS 14 (μ-Se) 3 (CN) 6 ] 6- , and [Re 12 CS 14 (μ-O) 3 (OH) 6 ] 6- , were isolated and their solid-state structures were elucidated by single-crystal X-ray diffraction analysis. Along with the previously reported μ-sulfide clusters, the new species constitute a series of rhenium anionic complexes with the common formula [Re 12 CS 14 (μ-Q) 3 L 6 ] 6- (Q = O, S, Se, L = CN - ; Q = O, S, L = OH - ), within which the total charge and number of cluster valence electrons (CVEs) are constant. The article presents insights into the mechanistic and synthetic aspects of the substitution process, and it comprehensively discusses the influence of inner ligand environment on the structure, spectroscopic characteristics, and electrochemical behavior of the novel compounds.

(103)Rh NMR parameters and the bonding structure of three complexes of [Cp*RhX2]2, where X = Cl, Br, or I, have been studied with the help of natural bond orbitals (NBOs) and natural localized molecular orbitals (NLMOs). The complexes of [Cp*RhX2]2, where X = Cl, Br, or I, have similar bonding structures, with the major difference being in the degree of covalency of the Rh-X bonds. The decomposition of (103)Rh NMR shielding into diamagnetic, paramagnetic, and spin-orbit terms shows that normal halogen dependence (NHD) of the (103)Rh NMR shift is defined mostly by the paramagnetic term, with the spin-orbit term being significantly smaller. The decomposition of (103)Rh shielding into spin-free NBO and NLMO contributions shows that (103)Rh shielding is dominated by Rh d-orbital deshielding contributions. We explain the NHD of the (103)Rh NMR shift with the increase in the energies of the virtual antibonding Rh-X orbitals along the X = Cl, Br, and I series.

The mechanism of inversion of lead phthalocyanine (PbPc), possessing a shuttlecock shape, was studied in detail within the bonding evolution theory framework. We have found that reaction pathway calculated using hybrid density functional theory (DFT) method, B3LYP, consists of five structural stability domains, which are connected by four bifurcation points. Reorganization of Pb's basins with pronounced role of core ones is the basis of the catastrophes identified, whereas basins belonging to other atoms are almost not involved in the electronic structure changing. These results provide the new topological picture of processes underlying the conformational transitions of shuttlecock-shaped metal phthalocyanines adsorbed on surfaces.

The synthesis and characterization of an organometallic trinuclear oxo-bridged niobium cluster complex with perpendicularly coordinated mu(3)-eta(2):eta(2)( perpendicular)-acetonitrile ligand in aqueous solution is reported. Reaction of NbCl(5) in acetonitrile with aluminum under argon followed by reaction with aqueous hydrochloric acid affords, after suitable workup, the isolation of the organometallic [Nb(3)(mu-eta(2):eta(2)-NCCH(3))O(3)(H(2)O)(9)](6+) aqua ion by cation-exchange chromatography. The purple niobium aqua ion in 2 M HCl shows a small peak at 365 nm (epsilon approximately 511 M(-1) cm(-1) per Nb) and a broad peak at 565 nm (epsilon approximately 335 M(-1) cm(-1)) in the UV-visible region. It is electron paramagnetic resonance (EPR)-active (g = 1.98), but no hyperfine interaction with the (93)Nb nuclear spin (I = 9/2) was observed. The cyclic voltammogram of [Nb(3)(mu-eta(2):eta(2)-NCCH(3))O(3)(H(2)O)(9)](6+) in 4 M HCl on edge-plane pyrolytic graphite electrode at 50 mV s(-1) in the potential range -1.2 V to +1.1 V (vs SCE) exhibits three anodic peaks at -0.12, +0.53, and +0.85 V and a large cathodic peak at -0.91 V with a slight shoulder at about -0.8 V. The purple aqua ion reacted with potassium thiocyanate to give the green thiocyanate derivative, which was crystallized as ((CH(3))(3)NH)(3)[Nb(3)(mu-eta(2):eta(2)-NCCH(3))O(3)(NCS)(9)].2.5H(2)O (1) and subjected to X-ray structure analysis. Density-functional theory (DFT) calculations fully supported the structure of the cluster.

It is shown that the abnormal long-range Te-Te intermolecular interaction in TeO(2) crystals may be related to the tunneling of electrons from the 5s(2) active lone pairs of Te(4+) ions and their partial delocalization on neighboring Te(4+).

By treatment of Zn-reduced ethanolic solutions of NbCl5 with HCl in the presence of sulfide followed by cation-exchange chromatography, two oxo-sulfido niobium aqua ions, the red [Nb4(mu4-S)(mu2-O)5(H2O)10]4+ and the yellow-brown [Nb5(mu3-S)2(mu3-O)2(mu2-O)2(H2O)14]8+, were isolated. Both readily form their respective thiocyanate complexes, for which the structure for the former has been previously reported. Brown crystals of (Me2NH2)6[Nb5S2O4(NCS)14].3.5H2O (1) were isolated in the case of the latter, and the structure was determined by X-ray crystallography (space group: a = 15.4018(5) A, b = 21.1932(8) A, c = 22.0487(8) A, alpha=gamma = 90 degrees , beta = 103.4590(10) degrees , and R(1) = 0.0659). An unprecedented pentanuclear Nb5S2O48+ core is revealed in which short Nb-Nb distances (2.7995(8)-2.9111(8) A) are consistent with metal-metal bonding. A stopped-flow kinetic study of the 1:1 equilibration of NCS- with [Nb4(mu4-S)(mu2-O)5(H2O)10]4+ has been carried out. Equilibration rate constants are independent of [H(+)] in the range investigated (0.5-2.0 M) and at 25 degrees C; kf= 9.5 M(-1) s(-1), kaq = 2.6 x 10(-2) s(-1), and K = 365 M1). Conditions with first NCS- and then [Nb4(mu4-S)(mu2-O)5(H2O)10]4+ in excess revealed a statistical factor of 4, suggesting the presence of four kinetically equivalent Nb atoms. Attempts to study the 1:1 substitution of NCS- with [Nb5(mu3-S)2(mu3-O)2(mu2-O)2(H2O)14]8+ showed signs of saturation kinetics. Quantum chemical calculations using the density functional theory (DFT) approach were performed on both the Nb4O5S4+ and Nb5O4S28+ naked clusters. The highest occupied and lowest unoccupied molecular orbitals have dominant Nb(4d) character. The HOMO for Nb4O5S4+ is a nondegenerate fully filled MO, whereas for Nb5O4S28+, it is a nondegenerate partially filled MO with one unpaired electron. EPR spectroscopy on [Nb5(mu3-S)2(mu3-O)2(mu2-O)2(H2O)14]8+ shows that the molecule has total anisotropy (C2v), with all three tensors, gx= 2.399, gy= 1.975, and gz= 1.531, resolved. No hyperfine interaction expected from the nuclear moment of I = 9/2 for 93Nb was observed.

The novel vanadium thiobromide, V4S9Br4, with a square-planar metal cluster core was synthesized and characterized by single-crystal X-ray diffraction, measurements of magnetic properties and the heat capacity, and DFT calculations of the electronic structure. At the room temperature, the compound displays paramagnetic properties with an independent spin on each V atom and with a weak exchange constant (J approximately 10 cm(-1)). The paramagnetic state is transformed into a low-spin state (AF-type ordering) at low temperatures. This change is accompanied by a heat-capacity anomaly. The observed magnetic and heat-capacity anomalies can be explained by the thermal excitation of electrons on the closely spaced molecular energy levels in the presence of the Jahn-Teller effect.