Construction of M–M bonds in late transition metal complexes

The 16-electron Co, Rh and Ir half-sandwich complexes of Cp^#M[E₂C₂(B₁₀H₁₀)] and Cp^#M(E₂S₂C₆H₄) (M = Co, Rh, Ir, Ru; E = S, Se) containing chelating 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolato ligands and benzenedithiolato ligands are promising precursors to build multimetallic clusters by reactions with low oxidation state late transition metal reagents. Such reactions lead to successful constructions of M–M bonds between iridium, rhodium, cobalt, ruthenium, and other late transition metals. Most of these complexes have been characterized by X-ray single crystal determinations and some have been studied by computational methods. Such theoretical studies reveal the covalent bonding nature of those multinuclear complexes. Some of these clusters have been found to have interesting nonlinear optical properties.     

N-picolinamido-N′-benzoylthiocarbamide transition metal complexes

A new series of CoII, NiII and CuII complexes derived from N-picolinamido-N-benzoylthiocarbamide has been prepared in which the Schiff base ligand is tridentate and/or bidentate, containing a potential ONS donor. The complexes have been characterized by elemental analyses, 1H-n.m.r., magnetic susceptibility, i.r., u.v., e.p.r. and thermal analyses. Stereochemistries are proposed for the complexes on the basis of the spectral and magnetic studies. The i.r. data indicate that the carbonyl oxygen of the benzoyl moiety constituents chelating backbone in most complexes.     

Kinetics of the photodecomposition of supramolecular alkynyl–phosphine complexes

Russian Journal of Physical Chemistry A - Kinetics of decomposition under the action of laser UV radiation is studied for alkynyl–phosphine complexes with bimetallic cores. It is shown that...     

Reactions of transition metal σ-acetylide complexes: IX. Preparation and properties of some cycloheptatrienylvinylidene complexes

Addition of [C₇H₇][PF₆] to iron, ruthenium or osmium alkynyl complexes has given eight cationic cycloheptatrienylvinylidene derivatives [M{C C(C₇H₇)R}(L)₂ (η-C₅H₅)][PF₆] (M = Fe, Ru or Os; R = Me, Pr, Ph or C₆F₅; L = PPh₃, L₂ = dppm or dppe; but not all combinations). With Fe(C₂Ph)(CO)₂(η-C₅H₅), only [Fe(CO)₂(thf)(η-C₅H₅)][PF₆] was obtained. Reactions of the new complexes are characterised by loss of the C₇H₇ group. The NMR spectra and FAB mass spectra are described in detail.     

Electronic structure of high-valent transition metal corrolazine complexes. The young and innocent?

This is a first quantum chemical study of corrolazine complexes. DFT calculations suggest that despite their extremely contracted central cavities, compared with porphyrins, a variety of corrolazine complexes may be expected to exist as stable compounds. The calculations also indicate that corrolazine complexes may be regarded as strongly electron-deficient analogues of corrole complexes. Thus, the calculated valence ionization potentials of P(V) and Cu(III) corrolazine derivatives are dramatically higher than those of analogous corrole derivatives. In addition, DFT calculations on Fe(IV) and Mn(IV) corrole and corrolazine derivatives suggest that compared with the often noninnocent corrole ligands, corrolazines are electronically more innocent and stabilize "purer" high-valent states of transition metal ions.     

Synthesis,structure and reactivity of complexes containing a transition metal–bismuth bond

The transition metal chemistry of bismuth has attracted significant interest since the 1970s. The low cost and high abundance of bismuth(III) reagents, such as the trihalides, makes them ideal starting materials and the size of the bismuth centre allows three- and higher-coordinate complexes to be synthesised, in which the bismuth atom is linked to one or more transition metal fragments. The ability to vary these metal fragments gives access to a plethora of available structures, with cyclopentadienylcarbonyl, metal carbonyl and sandwich compounds of bismuth in existence. Significant recent study has focused on applications in catalysis, where bismuth species can act as cross-coupling agents in carbon–carbon, carbon–nitrogen and carbon–oxygen bond forming reactions. Another striking feature is the variation in bonding situations that can be observed when studying the organometallic chemistry of bismuth. For example, dative and covalent interactions have been reported, in addition to cases of dibismuth acting as a two-, four- or six-electron donating ligand. This review aims to demonstrate the multi-faceted nature of the transition metal chemistry of bismuth and provide a detailed coverage of this topic.     

The possibility of semiconductor–metal transition in a spherical quantum dot

We observe an abrupt change in diamagnetic susceptibility at critical donor concentration for an $\text{ Al }_\mathrm{x}\text{ Ga }_\mathrm{1-x}\text{ As/GaAs }$ Al x Ga 1 ? x As/GaAs quantum dot system in the effective mass approximation indicating a possible semiconductor metal transition. The effect of confining potential and the laser intensity on the abrupt change in diamagnetic susceptibility has also been studied. The effect of nonparabolicity of the conduction band has been included in our calculations. Results are presented and discussed.     

Syntheses and crystal structures of transition metal complexes of 1,1′-bisacetylacetoferrocene

Bimetallic complexes 3a–e of 1,1′-bisacetylacetoferrocene (2) were prepared by reactions of transition metal acetates M(OAc)₂ (M?=?Co²⁺, Mn²⁺, Cu²⁺, Ni²⁺, Zn²⁺) with the 2 in refluxing methanol. The X-ray structures of the cobalt and manganese complexes were determined showing very similar centrosymmetric macrocyclic dimeric frameworks constituted by linkage of two Co²⁺ or Mn²⁺ ions and two 1,1′-diacetoacetylferrocene units with two additional methanols as bridges dividing this macrocyclic framework into two small cyclic subunits. The UV-Vis spectra and electronic properties were also studied.     

Reactions of transition metal σ-acetylides: VIII. Preparation and properties of some aryldiazo-vinylidene complexes

Fourteen aryldiazovinylidene complexes of ruthenium and osmium have been made by addition of aryldiazonium cations to the appropriate σ-acetylides. Their properties and spectra (including FAB-MS) are described, and reactions with MeOH, hydride and methoxide are reported. Addition to and protonation, alkylation, and cyclomanganation of the aryldiazo functions are also described.     

Photophysics of π-conjugated oligomers and polymers that contain transition metal complexes

There has been a surge of interest concerning the synthesis, optical and electronic properties of π-conjugated polymers that contain transition metal complexes. The integration of transition metal chromophores that feature metal to ligand charge transfer (MLCT) excited states into a π-conjugated polymer permits easy variation of the material’s optical and electronic properties. In this review, we survey a number of recent photophysical studies that examine π-conjugated oligomer or polymer/transition metal complex hybrids. The effects of the types of π-conjugated backbone, oligomer and polymer structure, the conjugation length and coordination to a variety of metal chromophores on the photophysics of the organic-metal hybrids are discussed. The degree of interaction between the polymer (or oligomer) and metal complex based excited states dramatically modulates the observed photophysics.     

Polymer-supported 2,2′-dipyridylmethane: catalytic activity of transition metal complexes in hydrogenations and oligomerizations

The palladium(II) acetate complex of the chelating ligand 2,2′-dipyridylmethane supported on polystyrene-2% divinylbenzene is an efficient catalyst for hydrogenation of alkenes and alkynes. Cyclopentadiene can be reduced with high selectivity to cyclopentene, but no selectivity is observed for the non-conjugated diene 1,5-cyclooctadiene. In the hydrogenation of 3-methylcyclohex-2-en-1-ol only small amounts of ketone are formed as a by-product, in contrast to the reaction catalysed by palladium on charcoal. Nickel(II) complexes of the same ligand catalyze the trimerization of butadiene to 1,5,9-cyclododecatrienes.     

The i.r. spectra of ethylenediamine complexes—I. The tris(ethylenediamine) complexes of first transition series metal(II) sulphates

The i.r. spectra of the complex [Zn(en)₃]SO₄ and its ⁶⁴Zn-, ⁶⁸Zn-, ¹⁵N-, N₂D₄- and C₂D₄-labelled analogues have been determined over the range 4000-50 cm⁻¹. Band assignments are based on the isotopically induced shifts and also those which result from substitution of Zn(II) by the metal(II) ions of the first transition series: Mn(II), Fe(II), Co(II), Ni(II) and Cu(II). The spectrum of the Cu(II) complex yields evidence of Jahn—Teller distortion.     

DNA modified with metal complexes: Applications in the construction of higher order metal–DNA nanostructures

DNA has recently emerged as a useful building block for higher order nanostructures, such as extended two-dimensional surfaces and discrete two- and three-dimensional structures. Transition metal complexes can introduce functionality to these otherwise passive nanostructures. This review examines the synthetic strategies used to introduce metals in a site-specific manner to DNA: either by attaching preformed metal complexes to DNA, or by metal coordination to unmodified or modified DNA. The applications of metal–DNA complexes in building higher order nanostructures and the utility of attaching luminescent or electrochemical labels are discussed.     

Synthesis, characterization, and antifungal studies of transition metal complexes of ω-bromoacetoacetanilide isonicotinylhydrazone

Isonicotinic acid hydrazide or isonicotinylhydrazide, commonly known as isoniazid, is an antibacterial agent that has been used to treat tuberculosis. It interacts with microbial cell walls. Schiff’s bases or anils are the compounds having >C=N−N< linkages, which have immense applications as catalysts, stabilizers, pigments, dyes, and drugs. They have good ability to form chelates with many metal ions. Isoniazid can form Schiff’s bases with diketones such as acetoacetanilide. Acetoacetanilide isonicotinylhydrazone and its metal chelates exhibit anticancer activity. Our studies on N-methyl-acetoacetanilide isonicotinylhydrazone and its metal chelates revealed that they are active against pathogenic fungal strains. Hence, it is worthwhile to synthesize new complexes of ligands having different substituents on the acetoacetanilide moiety. We synthesized five new metal chelates of ω-bromoacetoacetanilide isonicotinylhydrazone. The ligand behaved as a tridentate monoanion or as a tridentate dianion in the complexes. These compounds were characterized mainly by elemental analysis; conductivity measurements; and electronic, infrared, and nuclear magnetic resonance spectral studies. We also carried out antifungal studies of these compounds against four selected pathogenic fungal strains using a cup-plate technique. Both the ligand and its metal chelates were active against all fungal strains investigated. However, the chelates were found to be more active than the ligand.     

Mössbauer spectra of ferrous salts of transition metal cyano complexes. A survey

Ferrous salts of ten hexacyanometallates and three tetracyanometallates were obtained and their Mössbauer spectra interpreted according to recent structural models for these families of compounds. Ferrous ferrocyanide (Williamson White) and its ruthenium and osmium analogs prepared mechanochemically are stable for hours, allowing their study by Mössbauer spectroscopy and other related techniques. For ferrous salts of trivalent hexacyanometallate anions, the random distribution of anion vacancies is discarded and a model of two well defined relative positions of CN and H2O ligands around the Fe2+ is suggested. Iron was found octahedrally coordinated in tetracyanometallates.     

Synthesis of benzannulated spiroacetals using chiral gold–phosphine complexes and chiral anions

The development of an asymmetric gold-catalysed dihydroalkoxylation strategy for the synthesis of the 3′H-spiro[chroman-2,1′-isobenzofuran] spiroacetal ring system 5 is described. Spiroacetal was generated in up to 87:13 enantiomeric ratio using chiral gold–phosphine complexes and chiral silver phosphate Ag(S)-TRIP.     

The molecular electrochemistry of metal–organic metallamacrocycles

Considering that most metallamacrocycles possess redox-active metal nodes as well as redox-active linker ligands, the number of studies aimed at investigating that inherent property is astoundingly small. This microreview summarizes the most relevant, recent work on the electrochemistry of organometallic macrocycles. We hope that this article encourages further incentives to not only explore, but also exploit the inherent redox-activity of metal–organic macrocycles.     

The chemistry of the carbon–transition metal double and triple bond: annual survey covering the year 1999

This survey is intended to be a comprehensive summary of articles that report on the synthesis, reactivity, or properties of compounds featuring a multiple bond between carbon and a transition metal. Reactions which employ metal carbene complexes as transient intermediates generated through well-established routes [Russ. Chem. Bull. 48 (1999) 16] are not covered unless there is some effort to characterize the carbene complex intermediate. Although a determined effort has been made to include patents, in general only patents which are listed in or at the end of Organometallics section of Chemical Abstracts (Section 29) are included; patents which appeared in Chemical Abstracts in the year 1999 have been included. Only compounds which feature a multiple bond between one carbon atom and one transition metal are discussed in this survey, thus bridging carbene and carbyne complexes are not covered unless there is a multiple bond to at least one transition metal. The complexes of stable carbenes with transition metals have not been included; since the π-donation component of these complexes is minimal, there is no formal carbonmetal multiple bond [J. Chem. Soc., Chem. Commun. (1997) 1963; Polyhedron 16 (1997) 3879]. This survey has been divided into two sections, metal carbene (or alkylidene) complexes and metal carbyne (or alkylidyne) complexes; the carbene complex section represents the vast majority of this article. The metal carbene section has been organized according to metal, starting from the left side of the periodic table. The ionic model [R.H. Crabtree, The Organometallic Chemistry of the Transition Metals, second ed., Wiley-Interscience, New York, 1994, pp. 25–31] has been employed for the discussion of oxidation states and ligand electron count throughout this survey. A special section focusing on alkene metathesis has been included prior to the discussion of carbene complexes of individual metals. The metal carbyne section has been organized according to reaction type.     

The chemistry of the carbon–transition metal double and triple bond: Annual survey covering the year 2009

This is a review of papers published in the year 2009 that focus on the synthesis, reactivity, or properties of compounds containing a carbon-transition metal double or triple bond.