Specific features of the structure of germanium(IV) complexes with polybasic acids

The specific features revealed in the structure of germanium(IV) compounds with ligands in the form of anions of polybasic acids (monoamine, diamine, and triamine complexones, i.e., hydroxyethylidene-diphosphonic and carboxylic acids) have been considered. The influence of the individuality of specific acids on the structure type (mononuclear, binuclear, trinuclear, hexanuclear, polynuclear), the coordination mode of monodentate ligands and donor atoms of polydentate ligands (terminal, bridging, chelating, chelating-bridging), and variants of the coordination of polydentate ligands, i.e., anions of polybasic acids, with metal atoms (germanium, rare-earth elements, copper, barium), as well as on the dependence of the Ge-O bond length on the individual nature of ligands (OH, H₂O, O(oxo)) and donor atoms of polydentate ligands α- and β-O(carb), O(hydr), O(P)] and their function in the structure (terminal, bridging, chelating, chelating-bridging), has been analyzed using 28 homometallic and heterometallic complexes as an example.     

Ionic liquid mediated routes to polydentate oxygen-donor adducts of cerium(III) bromide

The preparation of a series of CeBr(3) molecular adducts supported by the polydentate oxygen donor ligands diglyme, dimethoxyethane and tetraglyme is reported. The new complexes are characterized structurally by X-ray diffraction and optically by photoluminescence studies.     

Non-heme iron(II) complexes are efficient olefin aziridination catalysts

Iron(II) complexes of polydentate nitrogen donor ligands catalyze the rapid aziridination of olefins by PhINTs.     

Guidelines to design new spin crossover materials

This review focuses on new families of spin crossover (SCO) complexes based on polynitrile anions as new anionic ligands or on polyazamacrocycles as neutral macrocyclic ligands. We have shown that the structural and electronic characteristics (original coordination modes and high electronic delocalization) of the polynitrile anions can be tuned by slight chemical modifications such as substitution of functional groups or variation of the negative charge to design new discrete or polymeric SCO systems.In our ongoing work on the design of new molecular systems based on new ligands that can be fine-tuned via chemical modifications, another promising way which has been recently developed in our group concerns the use of new neutral polydentate ligands which are able to tune the ligand field energy around the metal centre. Here we report some recent original Fe(II) SCO complexes based on such polydentate ligands.     

Synthesis and Properties of 2-(Diorganylphosphorylhydroxymethyl)-1-organylimidazoles

1-Organyl-2-formylimidazoles and -benzimidazoles react with diorganylphosphine oxides under mild conditions (room temperature, dioxane, 1 h) to give in practically quantitative yields 2-(diorganylphosphorylhydroxymethyl)-1-organylimidazoles - highly reactive synthons and polydentate ligands for the design of metal complex catalysts.     

Study of amino- and pyridyl-containing zinc(II) and cadmium(II) complexes by molecular mechanics using a force field based on the Gillespie-Kepert model

A new approach combining the molecular mechanics (MM) method and the Gillespie-Kepert model was applied to calculate the geometry and strain energy of zinc(II) and cadmium(II) complexes with amino- and pyridyl-containing ligands. High accuracy of calculations of the geometry was demonstrated for more than 20 complexes of these metals. Typical r.m.s. deviations between the calculated and experimental values (X-ray diffraction analysis) were 0.02 Å for bond lengths, 2° for bond angles, and 4° for torsion angles. The size-match selectivity of several macrocycles and polydentate open-chain ligands was studied. Correlations between the calculated strain energies of metal complexes and the experimental values of their stability constants and enthalpies of formation are discussed.     

Multicomponent Self-assembly:Spontaneous Formation of a Metallomacrocycle from Two Quinoline Based Linear Ligands and Four Silver(Ⅰ) Nitrates

Using metal ions to control the self-assembly of metallosupramolecules of varying architecture is one of the fascinating developments in supramolecular chemistry[1,2],particularly those concerned with the deliberate construction of molecular aggregates,like helices,rotaxanes,catenanes,knots,cages[3～6] and the crystal engineering of two or three dimensional networks with varied topology and interpenetration[7～10].Coordination bonds have proved themselves to be one of the most useful connectors in supramolecular self-assembly due to their versatile geometrical modes(e.g.linear,trigonal,square plane,tetrahedral,octahedral) in bond formations.By careful design of tailored ligands,various novel supramolecular architectures have been constructed.Recently,angular bi- or tridentate and other polydentate ligands have aroused a special interest,and a variety of molecular squares,boxes and cages[1～14] with internal cavity or void have been reported,in which many nanoscale structures are formed[6,15,16].We have been interested in the construction of metal based supramolecular structures with polydentate ligands[17～20] and herein report a new metallomacrocyclic complex assembled from two linear polydentate ligands and silver(Ⅰ) nitrate.     

Advances in the chemistry of hydrazinopyrimidines (review)

Research on methods for the preparation of hydrazinopyrimidines is reviewed. Ways to use hydrazinopyrimidines in the chemistry of pyrimidine and condensed systems that contain a pyrimidine ring and in the synthesis of polydentate ligands are examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 579–600, May, 1982.     

Hyperbranched polyester poly(3-diethylamino)propionates and their copper(<Emphasis Type="SmallCaps">ii</Emphasis>) complexes

Novel polydentate ligands were obtained from second and third generation hyperbranched polyesters containing terminal (3-diethylamino)propionate groups. Polynuclear Cu^II complexes with these ligands were synthesized. The degree of diethylamination of the polyesters increases when moving from the second to the third generation (from 56 to 81%). In polynuclear complexes, the ratios of Cu to hyperbranched ligand are 6 : 1 and 13 : 1 for second and third generation polyester polyamines, respectively. It was demonstrated using IR and ESR spectroscopy that each coordination polyhedron in the complexes is an isolated paramagnetic center of the formula CuN₂O₂Solv₂ (Solv = H₂O, DMSO).     

Synthesis of Novel Derivatives of Pyridine‐2,6‐dicarboxylic Acid

Two series of novel derivatives of pyridine‐2,6‐dicarboxylic acid with potential as polydentate ligands were synthesized from pyridine‐2,6‐dicarboxylic acid. All new compounds were characterized by NMR, MS, IR, and EA.     

Hyperbranched polyester poly[3-(morpholin-4-yl)propionates] and their copper(II) complexes

Novel polydentate ligands on the basis of second- and third-generation hyperbranched polyesters containing terminal poly[3-(morpholin-4-yl)propionate] groups and their 6 : 1 and 13 : 1 polynuclear copper(II) complexes were synthesized. The degree of functionalization of the polyesters with morpholine increases in going from the second (56%) to third generation (68%). According to IR and electronic spectroscopy data, each coordination entity in the complexes is an isolated paramagnetic center of the formula CuN₂O₂Solv₂ (Solv = H₂O, DMSO).     

Synthesis and crystal structures of Group 6 metal carbonyl complexes containing S-rich bis(pyrazol-1-yl)methane ligands

The reaction of 3(5)-methylthio-5(3)-phenylpyrazole with dibromomethane under phase-transfer catalytic conditions only affords a new ligand, bis(3-phenyl-5-methylthiopyrazol-1-yl)methane. However, the reaction of 3(5)-methylthio-5(3)-p-methoxyphenylpyrazole or 3(5)-methylthio-5(3)-tert-butylpyrazole with dibromomethane under the same conditions yields three isomers, respectively, indicating that the substituents significantly affect the steric and electronic properties of pyrazole ring during the formation of ligands. Treatment of these potential polydentate ligands with M(CO)₆ (M=Cr, Mo or W) under UV irradiation at room temperature affords (NN)M(CO)₄ derivatives, in which some complexes contain asymmetric substituted bis(pyrazol-1-yl)methane ligands. The X-ray crystal structure analyses indicate that the sulfur atoms in these complexes do not take part in the coordination to the metal centers, and S-rich bis(pyrazol-1-yl)methanes actually act as bidentate chelating ligands by two nitrogen atoms. It is also interesting that in order to reduce the repulsion of methyl groups with carbonyls, the methyl groups in these complexes are oriented away from the metal centers.     

Polynuclear π-allyl complexes of palladium (II)

Conclusions Polynuclear -allyl complexes of palladium (II) containing 5,5-methylenebis(salicylate) or polydentate Schiff bases as ligands were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1855–1856, August, 1972.     

Study on catalytic properties of the macromolecules containing pendant pyridine groups-supported rhodium complexes for the carbonylation reactions

The experiments reveal that anchoring rhodium(I) macromolecules containing pendant pyridine groups exhibit remarkably different carbonylation catalytic behaviours, depending on the quaternary degree of polymer ligands. The catalysts with the quaternized ligands are more active than that with the non-quaternized ligands, but the best of the lots isn't the highestly quaternized. A new structural type of the compounds called the polydentate hetero-bound rhodium(I) ion complexes is recognized to be responsible for higher carbonylation reactivities.     

Lanthanide mono(borohydride) complexes of diamide-diamine donor ligands: novel single site catalysts for the polymerisation of methyl methacrylate

Samarium chloride and borohydride complexes of the diamide-diamine ligands (2-C5H4N)CH2N(CH2CH2NR)2(R = SiMe3 or mesityl) are described; the borohydride compounds are the first polydentate amide-supported single component lanthanide catalysts for the controlled polymerisation of polar monomers, and also represent the first lanthanide borohydride complex for the polymerisation of methyl methacrylate.     

Synthesis of symmetrical di(pyrimidin-2-yl)-1,2,4-triazoles and di(pyrimidin-2-yl)-1,2,4,5-tetrazines

The reactions of pyrimidine-2-carbonitrile and 4,6-dimethylpyrimidine-2-carbonitrile with hydrazine hydrate were investigated. Intermediates in the route of successive transformations of pyrimidine-2-carbonitrile (pyrimidine-2-carbamidrazone and 1,2-bis[amino(pyrimidin-2-yl)methylidene]hydrazine) into trinuclear heterocyclic compounds, viz., symmetrical di(pyrimidin-2-yl)-1,4-dihydro-1,2,4,5-tetrazines and di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amines (potential polydentate ligands), were isolated. The oxidative dehydrogenation of di(pyrimidin-2-yl)-1,4-dihydro-1,2,4,5-tetrazines afforded the corresponding 3,6-di(pyrimidin-2-yl)-1,2,4,5-tetrazines.     

Isolation of an Eleven‐Atom Polydentate Carbon‐Chain Chelate Obtained by Cycloaddition of a Cyclic Osmium Carbyne with an Alkyne

Carbon ligands have long played an important role in organometallic chemistry. However, previous examples of all‐carbon chelating ligands are limited. Herein, we present a novel complex with an eleven‐atom carbon chain as a polydentate chelating ligand. This species was formed by the [2+2+2] cycloaddition reaction of two equivalents of an alkyne with an osmapentalyne that contains the smallest carbyne bond angle (127.9°) ever observed. Density functional calculations revealed that electron‐donating groups play a key role in the stabilization of this polydentate carbon‐chain chelate. This process is also the first [2+2+2] cycloaddition reaction of an alkyne with a late‐transition‐metal carbyne complex. This study not only enriches the chemistry of polydentate carbon‐chain chelates, but also deepens our understanding of the chelating ability of carbon ligands.     

A bis-acetonitrile two-coordinate copper(I) complex: synthesis and characterization of highly soluble B(C(6)F(5))(4)(-) salts of [Cu(MeCN)(2)](+) and [Cu(MeCN)(4)](+)

Copper(I)-acetonitrile complexes are exceedingly useful starting materials for the synthesis of copper(I) complexes with polydentate ligands. To extend the utility of such chemistry to solution studies in relatively low-dielectric solvents (i.e., diethyl ether, toluene) and to aid in obtaining products amenable to X-ray diffraction studies, we have recently begun to employ counteranions such as B(C(6)F(5))(4)(-) for bioinorganic studies. Thus, the synthesis of [Cu(MeCN)(4)]B(C(6)F(5))(4) (1) is presented. Its recrystallization from CH(2)Cl(2)/pentane yields the linear, two-coordinate complex [Cu(MeCN)(2)]B(C(6)F(5))(4) (2), whose centrosymmetric X-ray structure shows that its Cu-N distance is significantly shorter than that in other two-coordinate Cu(I) complexes with nitrogen ligands or that in the tetrahedral complex [Cu(MeCN)(4)]ClO(4). Infrared spectroscopy indicates interesting and diagnostically useful differences between the nu(CN) of 1 and 2.     

Double Michael addition of azoles to methyl propiolate: a straightforward entry to ligands with two heterocyclic rings

The synthesis of methyl bis(azol-1-yl)propionates is reported for the first time. These bridge-functionalized bis(azol-1-yl)methanes are prepared by a double Michael addition of azoles to methyl propiolate, representing a new methodology for the synthesis of polydentate ligands.     

Analysis of the selectivity of the complexation of complicated cyclopendants by molecular mechanics

The results of a calculation of the complex-forming conformations of two new organophosphorus polydentate ligands from the cyclopendant class, i.e., macrocyclic ligands with exocyclic groupings containing additional donor centers, have been presented. The compounds contain 1,4,7,10-tetraazacyclododecane as a macrocyclic fragment, and the pendant groups are methyl- and ethylphosphoryl groupings. The results of the construction of the probable ligand contour account for the high stability of the complexes with metal cations and the low complexation selectivity. The structure of the low-energy ligand contour of these compounds has a folded conformation for the macrocycle with conformational lability of the pendent groups, which does not favor the appearance of specific selective properties. The methods used to calculate complicated topological types of polydentate ligands have also been examined.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 6, pp. 655–661, November–December, 1986.