Two inorganic chains based on the Anderson-type polyanions and transition metals

Two new compounds based on Anderson-type polyanions, H(C₆H₉N₃O₂)₂[Mn(H₂O)₂][Al(OH)₆Mo₆O₁₈] ? 6H₂O (1) and (C₆H₁₀N₃O₂)₂[Ag(H₂O)₂][Cr(OH)₆Mo₆O₁₈] ? 6H₂O (2), have been synthesized in aqueous solution and characterized by elemental analyses, IR, TG, and single crystal X-ray diffraction. Both compounds show inorganic 1-D chain-like structures in which the Anderson-type polyanions are bidentate ligands chelating to two metal cations. Further, transition metal cations are in the same line with the center Al (Cr), which is unusual in 1-D inorganic chains based on Anderson-type polyanions. Free histidine molecules further link the chains into 3-D supramolecular frameworks via hydrogen interactions. Electrochemical and fluorescence quenching properties were investigated.     

Semi-empirical calculation method for transition metals

A semi-empirical molecular orbital method capable of giving useful bond energy and bond geometry information about transition metal compounds is presented. In this method, which for the first time applies a MINDO procedure to transition metals, the one electron part of the off diagonal Fock matrix elements are put proportional to overlap divided by inter-nuclear distance rather than being proportional to overlap as is conventional. Good results are obtained for FeH, FeH₄, Fe₂, Fe₆, Fe(CO)₅, FeO, O-Fe-O, and FeO₂ (side- and end-bonded).     

Indo parameters for the first-and second-row transition metals

A system of INDO parameters F⁰(ij) and U_ii for the first-and second-row transition metals is proposed. The system correctly reproduces the energies of the lowest terms of dⁿ, dⁿ⁻¹s, dⁿ⁻²s², dⁿ⁻¹p, and dⁿ⁻²sp configurations of M⁰ atoms and M¹⁺ ions. The parameters are estimated from spectroscopic values of energies of the terms and F^k(ij) and G^k(ij) parameters. St. Petersburg State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4, pp. 3–11, July–August, 1994. Translated by O. Kharlamova     

Role of ligands in homogeneous catalysis based on transition metals

The role of ligands in homogeneous catalysis by transition metals and the promising lines of research related to simulation of biocatalytic processes are considered.     

Aryloxide-based multidentate ligands for early transition metals and f-element metals

This article presents an overview of the chemistry of early transition metal and f-element complexes stabilized by aryloxide-based multidentate ligands. Preparations and reactivity studies of these compounds are discussed. The presence of the bridging units in this ligand system imposes a strong geometry constraint to the aryloxide groups, which leads the way to novel patterns of structure and reactivity.     

Dihydrogen complexes of the transition metals

Summary The binding and activation of dihydrogen by simple transition metal complexes is of fundamental importance in processes as diverse as the homogeneous or heterogeneous hydrogenation of unsaturated organic molecules⁽¹⁾ and understanding how metalloenzymes such as nitrogenase⁽²⁾ and the hydrogenases⁽³⁾ work at the atomic level.Simple consideration of the oxidative-addition of dihydrogen to a coordinatively-unsaturated complex {or its reverse (reductive-elimination)} reveals that the reactions are compelled to proceed via a dihydrogen complex as shown in Equation (1). However until recently it was considered that the dihydrogen complex had only a fleeting existence. Although there had been some reports in the literature such as that by Ashworth and Singleton⁽⁴⁾ that the formally Ru^IV trihydride, [RuH₃(PMe₂Ph₂]⁺ was better formulated as the Ru¹¹ species [RuH(H₂)(PMe₂Ph)₂]⁺, these could not be substantiated. In 1984, though, Kubas showed that the apparently innocuous complex [WH₂(CO)₃(PPr ₃ ⁱ )₂] contained the side-on bonded dihydrogen molecule, established unambiguously by x-ray, and neutron crystallography and spectroscopy⁽⁵⁾. In this highlight the current status of dihydrogen complexes, their structure, identification and in particular their reactivity will be discussed.     

Quantum chemical study of catalysts based on oxides of transition metals

Catalysts based on oxides of transition metals were studied by X α–DV calculations. The chemical composition and electronic structure of surface layers for platinum(IV) oxide catalysts modified under percompound electrosynthesis were determined by X-ray photoelectron spectroscopic, quantum chemical, and electrochemical data. The main regularities in electronic structure change under the transition from solid pure oxide PtO₂ to its, in part, N-substituted PtO_2–xN_x were analyzed. Then, we looked for perspective catalysts, calculating the electronic structure for analogous compounds of Ir(III), Ir(IV), Rh(III), and Pd(II). We found that the changes in electronic structure of rhodium oxide under O—N-substitution allowed us to predict the excellent properties of its compound as a catalyst for percompound electrosynthesis reactions. © 1994 John Wiley & Sons, Inc.     

Framework materials based on azamacrocyclic complexes of transition metals and carboxylates

Published data on the molecular and crystal structure and characteristics of coordination polymers and metal-organic frameworks based on the macrocyclic complexes of transition metals and aromatic carboxylates are analyzed. The prospects for the use of such materials as selective sorbents for gases and organic molecules are demonstrated.Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol. 40, No. 6, pp. 331–356, November–December, 2004.     

Gaussian basis sets for transition metals of the second series

A Gaussian basis set consisting of (15s, 9p, 8d) Gaussian functions has been optimized for the transition metal atoms of the second series (fourth-row atoms).     

On the dioximine complexes of transition metals

Twelve new complexes NH₄[Co(DH)₂(SO₃)(amine)]·t H₂O (DH ₂=dimethylglyoxime) have been synthesized and characterized. Their i.r. spectra show the SO₃ to be co-ordinated to the Co atom through the S atom. The thermal decompositions of a series of derivatives of this type have been investigated with a derivatograph. The first process is an endothermic dehydration reaction, occurring in a single stage or in two successive ones. The loss of the crystallization water is followed by another endothermic reaction, without a clear stoichiometry, which is referred to as deamination. At higher temperatures, exothermic pyrolysis processes occur. From the TG curves, kinetic parameters have been derived for the dehydration and deamination reactions.

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Zusammenfassung Zwölf neue Komplexe der allgemeinen Formel NH₄[Co(DH)₂(SO₃)(amin)]·t H₂O (DH=Dimethylglyoxim) wurden synthetisiert und charakterisiert. Die IR-Spektren zeigen, daß SO₃ über das S-Atom koordinativ an das Co-Atom gebunden ist. Die thermische Zersetzung einer Reihe von Derivaten dieses Typs wurde mittels eines Derivatographen untersucht. Der erste Prozeß ist die in einem einzigen oder in zwei aufeinander folgenden Schritten verlaufende endotherme Dehydratisierung. Auf die Abgabe des Kristallwassers folgt eine andere endotherme Reaktion unklarer Stöchiometrie, die als Deaminierung bezeichnet wird. Bei höheren Temperaturen verlaufen exotherme Pyrolyseprozesse. Aus den TG-Kurven wurden kinetische Parameter für die Dehydratisierung und die Deaminierung bestimmt.

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NH₄Co(DH)₂(SO₃)(a)]·tH₂O, DH ₂ — . , . . , . «». . .

     

Fluorescent sensing of transition metal ions based on the encapsulation of dithranol in a polymeric core shell architecture

The encapsulation behaviour and the resulting transition metal ion sensing capabilities of a 5-arm star-shaped polymer bearing terpyridine ligands on its periphery are described.     

Microchip based sample treatment device interfaced with ICP-MS for the analysis of transition metals from environmental samples

A downscaled solid phase (SPE) device applicable for sample preparation prior to ICP-MS monitoring, have been constructed making use of the lab on a chip concept. Standard photolithography and wet chemical etching were used to fabricate glass microfluidic devices accommodating three microchannels, each of them incorporating a defined section that could be packed with SPE materials; selective chelating resin. The microfluidic device was interfaced with the ICP-MS instrument throughout a low flow rate concentric nebuliser using a Teflon connector, and coupled with a flow injection manifold delivering samples and reagents via a manually operated splitting valve. The feasibility of the miniaturized prototype to perform SPE of trace metals was proved by analyzing trace metals, Cd, Co, and Ni, in seawater reference materials; CASS-2 and SLEW-1. The obtained result was in good agreement with the certified values. The device could be used as a remote miniaturized sample treatment for field work.     

Norbornadiene complexes of transition metals

Conclusions Correlations were established between the stereochemistry of 2-(-carbinol)norbornadiene complexes of rhodium and their mass spectra.This study is also communication 30 from the series Mass Spectrometry of Transition Metal- Complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2701–2703, December, 1982.     

Control of axial chirality in absence of transition metals based on arynes

The modular construction of enantioenriched biaryl derivatives is presented. This approach is based on (1) an almost quantitative access to polybrominated precursors via a transition metal-free aryl–aryl coupling, the ARYNE coupling, (2) the regioselective introduction of a traceless chiral auxiliary (an enantiopure para-tolylsulfinyl group), (3) the chemoselective functionalization of this auxiliary, and (4) subsequent regioselective functionalization of the remaining bromine atoms without any racemization during these steps. Next, the atroposelective coupling of in situ generated arynes and aryllithiums bearing various chiral auxiliaries (tert-butyl sulfoxide, para-tolyl sulfoxide, and tartrate-derived chiral diethers and oxazolines) is described and applied to the formal synthesis of (−)-steganacin.     

Atomic natural orbital basis sets for transition metals

Summary We show that atomic natural orbitals are an excellent way to contract transition-metal basis sets, even though the different low-lying electronic states may have very different basis set requirements.     

Extended-Hückel parameters for third-row transition metals

A parameter set for valence orbital ionization potentials (VOIP's) of 5d transition metals has been derived from their atomic spectra. The set, which can be used for Extended-Hückel calculations, includes relativistic effects on orbital energies. It is thus helpful for quantum-chemical explanations of chemical differences between complexes of 4d and 5d transition metals.