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Tris(2,2′-bipyridyl)ruthenium(II) dichloride [Ru(bpy)3Cl2] and analogous complexes have been studied extensively in the literature due to their luminescent and photochemical properties as well as their excited-state lifetimes. Conducting polymers with similar ruthenium groups have also been investigated for various applications. In this study, syntheses of four ruthenium complexes with a polymerizable tridentate ligand, bis[4-[2-(3,4-diethylenedioxy)thiophene]pyrazol-1-yl]pyridine (EDOT2NNN), and with bidentate ligands, two of which were anionic (hfac: 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; dbm: dibenzoylmethane) and two of which were neutral (bpy: 2,2′-bipyridyl; phen: 1,10-phenanthroline), were achieved for potential OLED/PLED applications. Saturated CH2Cl2 solutions of monomers were oxidatively and electrochemically polymerized, and the scan rate dependences of the polymers were measured. UV–vis spectroscopic characterizations of the complexes and the EDOT-functionalized ligand were obtained. [Ru(EDO...

Carbonyl complexes of molybdenum with the phosphorus/nitrogen/phosphorus ligand, PNP-Mo(CO)n, where n = 3, 4 and PNP is N,N-bis[2-(diphenylphosphino)ethyl]phenylamine have been synthesized and characterized by 1H, 31P{1H} NMR, IR (ATR and solution state), Raman, X-ray diffraction, MS and elemental analysis. DFT calculations of the complexes were also performed. The PNP-Mo(CO)4 complex in which the binding mode is bidentate cis-phosphine and, facial and meridional isomers of PNP-Mo(CO)3 in which the binding mode is tridentate were obtained. The facial isomer and the tetracarbonyl complexes were successfully synthesized and purified; however, it was not possible to isolate the meridional isomer. Only a few crystals of the meridional isomer were detected and used for X-ray analysis. When the facial isomer was dissolved in CH2Cl2 or in THF, it was found to undergo decomposition thereby generating the tetracarbonyl complex, meridional isomer, Mo(0) as a dark precipitate along with some facial isomer that was left intact in solution. The reason that the facial isomer was the preferred structure with respect to the meridional isomer was also investigated.

Research in functionalized inorganic supports faces special challenges regarding the inmobilization of organic chains and efficient computational methods for the quantum chemical modeling of coordination compounds. The silylant 3-cloropropyltriethoxysilyl (R1) was anchored over silica gel in anhydrous conditions, in order to react with diethyl Iminodiacetate (DIDA) to obtain modified silica gel (R2), which was hydrolized in basic conditions previously synthesized and characterized by S BET, TGA and FTIR spectroscopy to obtain iminodiacetic acid groups IDA to prepare an modified inorganic support (R3) that is able to get hands on metals from the first transition series such as copper and nickel. The obtained experimental values showed that the functionalized grade of R3 corresponds to 0.1598 mmol of the nitrogen indicated that the adsorbed Cu(II) or Ni(II) have the stoichiometry for both cation of 1:1. Based on this relation, the three different structures were proposed to carry out the computational studies using density functional theory (DFT) in its LDA and PW91 with the TZP slater type basis set. The primary coordination sphere of copper(II) or nickel (II) ion in R3 are optimized, structural parameters are calculated, vibrational bands are assigned and energy gaps of frontier orbital (HOMO–LUMO) have been calculated. The calculated results reproduced the experimental data with good agreement. An energy decomposition analysis (EDA) of the different models proposed here was performed and suggest a 1:1 coordination form.

Trinuclear nickel complexes have been isolated and characterized. These complexes resulted from reaction with the constrained α–β dioxime congener of phenanthrene-9,10-dione., A trinuclear nickel complex of phenanthrene-9,10-dione dioxime (H2pqd), namely bis­[μ2-9,10-bis­(oxido­imino)­phenanthrene]­bis­[μ2-10-(oxido­imino)phenanthrene-9-one oxime](phenanthrene-9,10-dione dioxime)trinickel(II) toluene disolvate, [Ni3(C14H8N2O2)2(C14H9N2O2)2(C14H10N2O2)]·2C7H8, has been isolated and its crystal structure determined. This complex features three independent NiII atoms that are arranged in a triangular fashion along with five supporting ligands. There are two square-planar NiII atoms and a third pseudo-octa­hedral NiII atom. While the square-planar NiII atoms are stacked, there are no ligand bridges between them. Each square-planar NiII atom, however, bridges with the pseudo-octa­­hedral NiII atom through Ni—N—O—Ni and Ni—O—Ni bonds. A fluorido­bor­ation reaction of the proton-bridged species gave the analogous complex bis­(μ2-bis­{[10-(oxido­imino)-9,10-di­hydro­phenanthren-9-yl­idene]amino}di­fluorido­borato)(phenanthrene-9,10-dione dioxime)trinickel(II) dichloromethane trisolvate, [Ni3(C28H16BF2N4O2)4(C14H10N2O2)]·3CH2Cl2, which shows the same binding structure, but features a widened Ni—Ni inter­action between the square-planar NiII atoms. The proton-bridged complex completes the macrocyclic coordination around the square-planar NiII atoms by means of an O—H⋯O hydrogen bond. Both compounds feature O—H⋯N hydrogen bonds between the oxime and the N atoms attached to square-planar nickel atom. The nickel units show no direct inter­action with their nearest neighbors in the extended lattice. Two π-stacking inter­actions between adjacent mol­ecules are found: one with a centroid–centroid distance of 3.886 (2) Å and the other with a centroid–centroid distance of 4.256 (3) Å. In the latter case, although not aromatic, the distance to the centroid of the central phenanthrene ring is shorter, with a distance of 3.528 (3) Å. Toluene mol­ecules occupy the solvent channels that are oriented along the c axis. In the fluorido­boronate structure, the solvent (DCM) was too badly disordered to be modelled, so its contribution was removed using SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9–18].

Reported here are the syntheses and characterization of cobaloximes that feature a bis(imino)acenaphthene (BIAN) appended ligand. The X-ray crystal structures and spectroscopy (1H NMR or EPR) of the complexes within the series [Co(aqdBF2)2(MeCN)2] (1), [Co(aqdBF2)(MeCN)2]− (2) and [Co(aqdBF2)2(MeCN)2]2− (3, 3′) are reported and the 3-electron reduced complex [Co(aqdBF2)2(MeCN)2]3− (4) has been prepared in situ and characterized by 1H NMR spectroscopy. The X-ray crystal structures revealed the presence of a 6-coordinate CoII species (1), a 5-coordinate CoI species (2), and a 4-coordinate complex (3, 3′). In the case of complex 3, evidence from single crystal EPR spectroscopy (g‖ = 2.017, g⊥ = 1.987

The synthesis and catalytic properties of two new 1,2-acenaphthenyl N-heterocyclic carbene-supported palladium(II) catalysts are presented. The acenaphthenyl carbene has been prepared with mesityl or 1,5-diisopropyl N-aryl substituents. Comprehensive catalytic studies for the Suzuki coupling of aryl halides with aryl boronic acids have been conducted. In general, the diisopropyl-functionalised catalyst showed superior selectivity and reactivity. A comparison of the catalytic performances in dichloromethane, toluene and water at low temperatures (30–40 °C) is also presented. Both catalysts were proficient in the homogeneous Suzuki coupling of aryl iodides, bromides and chlorides with boronic acids in dichloromethane. Similar reactions in water led to the formation of insoluble colloidal catalytic species that still exhibited high activity in the Suzuki reaction with aryl chlorides. Reactions performed in toluene showed intermediate results; partial catalyst decomposition led to concomitant homogeneous and heterogeneous catalysis. The heterogeneous palladium precipitates could be easily recovered by filtration and reactivated for subsequent use. Activation energies determined for aryl bromide-based Suzuki reactions were found to be in the range of 159–171 kJ mol−1 in organic solvents and 111–116 kJ mol−1 in water. The corresponding activation energy for the aryl chloride was found to be 322 kJ mol−1 in water.

Four new, pincer type copper complexes 5–8 were synthesised from the reactions of CuCl2·2H2O with respective hydrazide ligands 1–4 (HL1–HL4) and characterized by various physicochemical techniques. The single crystal XRD and spectral data revealed that all the ligands are monoanionic, tridentate pincer analogues chelating agent, which coordinate via ONN donor atoms to the copper ion. The effect of electronegativity and ring size of heterocyclic hydrazide moiety of ONN pincer type copper(II) chelates on nucleic acid interaction and protein binding was investigated by in vitro experiments. In addition, scavenging activity and cytotoxicity of the newly synthesized complexes of the composition [Cu(L1–4)Cl] were also evaluated.

The title molecule, C64H74N4, consists of a pyrene backbone with imine moieties located on the 4-, 5-, 9-, and 10-positions of the ring system. The aryl groups on these imines are sterically bulky 2,6-diisopropylphenyl units. As a consequence, the backbone itself is twisted, with an angle of 15.29 (6)° between the mean planes (r.m.s. deviations = 0.006 and 0.009 Å) of the phenyl units. The N=C—C=N units are significantly twisted and feature torsion angles of −48.8 (2) and −46.3 (3)°. The non-planarity of the backbone and short C—N distances [ranging from 1.281 (2) to 1.285 (2) Å] indicate the lack of conjugation in the molecule and double-bond nature of the imines. Weak intramolecular and intermolecular C—H...π interactions are observed.

Three new transition metal complexes of the type ML2 (where M = Ni(II), Co(II) or Cu(II); HL = N′-[phenyl(pyridin-2-yl)methylidene]furan-2-carbohydrazide]) have been prepared by treating [NiCl2(PPh3)2], [CoCl2(PPh3)2] or [CuCl2(PPh3)2] with N′-[phenyl(pyridin-2-yl)methylidene]furan-2-carbohydrazide derived from furoic acid hydrazide and 2-benzoyl pyridine wherein the hydrazone ligand (L) coordinated to the respective metal ions in 1:2 stoichiometry to mononuclear octahedral complex. The crystal structure of the complexes [NiL2] (1), [CoL2] (2) and [CuL2] (3) solved using single crystals revealed a distorted octahedral geometry around the metal ion involving the coordination of an azomethine nitrogen, a pyridine nitrogen and an enolic oxygen derived from deprotonation of the ligand. From the bioinorganic application point of view, a detailed work on the binding of the complexes 1, 2 and 3 with CT DNA as well as BSA was undertaken along with DNA cleavage. In vitro assay on the antioxidant activity of the above complexes and hydrazone ligand revealed that they possess significant antioxidant activity. However, among the newly synthesized hydrazone complexes, complex 3 having coordinated Cu2+ ion in its molecular structure exhibited superior activity in all the biological studies in comparison with the other two complexes possessing nickel and cobalt ions with same ligand (L).

Divalent Co, Ni and Cu hydrazone complexes containing [N'-(phenyl(pyridine-2-yl)methylidene) benzohydrazide] ligand were synthesised and characterised. Interactions of these complexes with DNA revealed an intercalative mode of binding between them. Further, all the hydrazone chelates showed moderate ability to cleave pUC19 DNA. Synchronous fluorescence spectra proved that the interaction of metal complexes with bovine serum albumin (BSA) resulted in a conformational change of the latter. Assay on the cytotoxicity of the above complexes against HeLa tumor cells and NIH 3T3 normal cells revealed that the complexes are toxic only against tumor cells but not to normal cells. In all the biological assays, the complex with copper ion as the metal center showed enhanced activities than the other two.

Two new aromatic carboxylic acids, namely, 3,5-bis(benzyloxy)benzoic acid (HL1) and 3,5-bis(pyridine-2-ylmethoxy)benzoic acid (HL2), have been prepared by replacing the hydroxyl hydrogens of 3,5-dihydroxy benzoic acid with benzyl and pyridyl moieties, respectively. The anions derived from HL1 and HL2 have been used for the support of a series of lanthanide coordination compounds [Eu(3+) = 1-2; Tb(3+) = 3-4; Gd(3+) = 5-6]. The new lanthanide complexes have been characterized on the basis of a variety of spectroscopic techniques in conjunction with an assessment of their photophysical properties. Lanthanide complexes 2, 4, and 6, which were synthesized from 3,5-bis(pyridine-2-ylmethoxy)benzoic acid, were structurally authenticated by single-crystal X-ray diffraction. All three complexes were found to exist as infinite one-dimensional (1-D) coordination polymers with the general formula {[Ln(L2)(3)(H(2)O)(2)]·xH(2)O}(n). Scrutiny of the packing diagrams for 2, 4, and 6 revealed the existence of interesting two-dimensional molecular arrays held together by intermolecular hydrogen-bonding interactions. Furthermore, the coordinated benzoate ligands serve as efficient light harvesting chromophores. In the cases of 1-4, the lowest energy maxima fall in the range 280-340 nm [molar absorption coefficient (ε) = (0.39-1.01) × 10(4) M(-1) cm(-1)]. Moreover, the Tb(3+) complexes 3 and 4 exhibit bright green luminescence efficiencies in the solid state (Φ(overall) = 60% for 3; 27% for 4) and possess longer excited state lifetimes than the other complexes (τ = 1.16 ms for 3; 1.38 ms for 4). In contrast to the foregoing, the Eu(3+) complexes 1 and 2 feature poor luminescence efficiencies.

The coordination of decamethyleuropocene to a “clamshell” 1,2-bis(imino)acenaphthene (BIAN) ligand is accompanied by a one-electron redox process. The crystal structure of the Eu3+ product has been determined. The complex crystallizes in the triclinic space group P-1, with a = 12.065(2), b = 15.391(3), c = 17.266(4) A, α = 73.71, β = 73.93(3), γ = 81.40(3)°, V = 2948.3(10) A3 and Z = 2. The pyridine moiety of the clamshell ligand is not coordinated to the Eu3+ center. A decamethyleuropocene complex of a “clamshell” ligand has been prepared and structurally characterized.

A brief review of our work on orthogonally-positioned NHC metallopolymers is highlighted herein. Some pertinent literature is presented, followed by the synthetic strategy employed as well as comprehensive electrochemical analyses. Derivatization of a suitable diimine into a electropolymerizable gold (I) NHC complex resulted in the first orthogonally-positioned NHC metallopolymer. Extension of this methodology to prepare analogous group 11, iridium and sulfur-substituted metallopolymers generated thin films with electrochromic activity that could be tuned by proper selection of the metal center.

A series of poly(N-heterocyclic carbene) complexes in which the carbene functionalities are orthogonally connected to the main chains of the respective polymers have been synthesized via oxidative electropolymerization of various bis(bithiophene)-substituted monomers with appended transition metal or main group entities (M = Ir, Au, Ag, or S). The polymers were characterized using a range of electrochemical, X-ray photoelectron spectroscopy, UV-vis spectroscopy, profilometry, and four-point probe conductivity measurements. Most of the polymers exhibited an intense absorbance wave at 700 nm under oxidative conditions which was attributable to the formation of polarons along the main chains. The iridium-containing thin film poly(8) was found to possess a significant NIR absorbance at 1100 nm in which the metal moiety effectively functioned as an electron sink. Electrochemical analyses of the polymer thin films revealed that they exhibited highly reversible electrochromic phenomena.

Three new binuclear lanthanide complexes of general formula [Ln(2)(L)(6)(H(2)O)(4)] (Ln = Tb (1), Eu (2), and Gd (3)) supported by the novel aromatic carboxylate ligand 4-(dibenzylamino)benzoic acid (HL) have been synthesized. Complexes 1 and 2 were structurally characterized by single-crystal X-ray diffraction. Both 1 and 2 crystallize in the triclinic space group P(1), and their molecular structures consist of homodinuclear species that are bridged by two oxygen atoms from two carboxylate ligands via different coordination modes. The discrete bridged dimer of 1 is centrosymmetric and features 8-coordinate terbium atoms, each of which adopts a distorted square-antiprismatic geometry. Both coordination spheres comprise two eta(2)-chelating benzoates, two mu-eta(1):eta(1)-carboxylate interactions from the bridging benzoates, and two water molecules. By contrast, in complex 2, the Eu(3+) ion coordination environment is best described as a distorted tricapped-trigonal prism, each europium ion being coordinated to three eta(2)-chelating benzoate ligands and two water molecules. One of the eta(2)-carboxylate ligands is involved in a further interaction with an adjacent metal, thus rendering the overall binding mode bridging tridentate, mu-eta(2):eta(1). Scrutiny of the packing diagrams for 1 and 2 revealed the existence of a one-dimensional molecular array that is held together by intermolecular hydrogen-bonding interactions. The Tb(3+) complex 1 exhibits high green luminescence efficiency in the solid state with a quantum yield of 82%. On the other hand, poor luminescence efficiency has been noted for the Eu(3+)-4-(dibenzylamino)benzoate complex.

Bis(imino)acenaphthenes (BIAN) have been known for many years. However, it is only since the 1990s that such compounds have been recognized as robust ligands for the support of catalytically active transition metal centers. More recently, the unique stereoelectronic properties of the BIAN ligand class are beginning to be appreciated and exploited for some fascinating new developments in synthetic, structural and catalytic s- and p-block chemistry.

The stable 3,3’-bridged biscarbenes, 1,4- and 1,3-bis[1-alkyl-4-phenyl-1,2,4-triazol-5-yliden-3yl]benzenes (5а,b,d) and 1,3-bis[1-(1-adamantyl)-4-phenyl-1,2,4-triazol-5-yliden-3-yl]butane (5c) have been prepared. Treatment of 5b with copper (I) chloride in tetrahydrofuran/acetonitrile solution and cobalt (II) chloride in acetonitrile or acetonitrile/toluene solution afforded the biscarbene copper (I) complex 8. The reactions of 5d with diphenyldiazomethane and sulfur resulted in the novel bisthione 6 and bisazine (7) derivatives, respectively. The X-ray crystal structures of 5d, 8 were determined.

Four new lanthanide(III) complexes of 2-thiopheneacetic acid (HTPAC), [Tb(TPAC)3·H2O]n (1), [Gd(TPAC)3·H2O]n (2), [Tb(TPAC)3(phen)]2 (3) and [Tb(TPAC)3(bath)]2 (4) (phen = 1,10-phenanthroline; bath = bathophenanthroline) have been synthesized and characterized by various spectroscopic techniques. The X-ray structure of 1 reveals that each Tb3+ ion is connected to two neighboring ions by six thiopheneacetic acid ligands via the carboxylate groups to form an infinite one-dimensional polymer. The unit cell contains only one independent crystallographic site for the Tb ions. The carboxylate groups of the six molecules of the thiopheneacetate ligands are coordinated in both bidentate bridging and tridentate chelate-bridging modes. Each Tb3+ ion is coordinated by nine oxygen atoms in an overall distorted tricapped trigonal-prismatic geometry. Eight of the oxygen atoms are furnished by the carboxylate moieties, and the remaining oxygen atom is provided by the water molecule. The photophysical properties of these complexes in the solid state at room temperature have been investigated. The quantum yields of 3 (4.43 ± 0.44 %) and 4 (9.06 ± 0.90 %) were found to be significantly enhanced by the presence of the bidentate nitrogen donor ligands in comparison with that of 1 (0.07 ± 0.01 %) due to effective energy transfer from the secondary ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The stable biscarbenes, 1,4- and 1,3-bis[1-(1-adamantyl)-3-phenyl-1,2,4-triazol-5-yliden-4-yl]benzenes (4a,b) have been prepared. Treatment of 4b with copper(I) chloride and copper(I) iodide in acetonitrile or acetonitrile/toluene solution afforded the biscarbene copper(I) complexes 5a and 5b, respectively. The reactions of 4a and 4b with diphenyldiazomethane and sulfur resulted in the novel bisazine (6) and bisthione (7) derivatives, respectively. The X-ray crystal structures of 4a and 5b were determined.

Four stable carbenes, 1-tert-butyl-3,4-diaryl-1,2,4-triazol-5-ylidenes 1a-d, including new fluorine-containing compounds 1c,d, react with a malonic ester to afford heterocyclic zwitterionic compounds 5a-d. The reactions with more acidic compounds (ethyl acetoacetate, malononitrile and 1,3-dimethylbarbituric acid) proceed with substrate deprotonation to form the respective azolium salts 6a-c. The X-ray crystal structure of 5a was also determined.

Salts containing the decamethylmetallocenium cations, [(C(5)Me(5))(2)M](+) (or Cp*(2)M(+)) of the group 13 "metals" B, Al and Ga have been prepared using a variety of synthetic routes. Precursor molecules of the type Cp*(2)MX (X=Cl, Br, Me) exhibit structural features that vary significantly depending on the size and electronegativity of the central atom. While salt metathesis, halide abstraction and methanide abstraction methods represent viable routes for the preparation of salts of Cp*(2)B(+) and Cp*(2)Al(+), acidolysis of a Cp* group from Cp*(3)Ga is the most reliable method for the synthesis of the analogous gallium cation. Gallocenium cations are less stable than either of the lighter congeneric cations since they prove to be susceptible to decomposition reactions involving the "back-transfer" of ligands from the counter anion. Density functional theory (DFT) calculations revealed that, whereas Cp*(2)Ga(+) is predicted to adopt a molecular structure more similar to that of Cp*(2)B(+), the electronic structure of the gallium cation bears a greater resemblance to that of Cp*(2)Al(+).

A base-stabilized mononuclear aluminum dication has been prepared by extrusion of two triflate anions from a precursor β-diketiminate-supported aluminum bis(triflate) using the tris(2-aminoethyl)amine (tren) ligand.

Three new homodinuclear lanthanide(III) complexes of xanthene-9-carboxylic acid, [Ln2(XA)6(DMSO)2(H2O)2](Ln = Eu (1), Tb (2) and Gd (3); HXA = xanthene-9-carboxylic acid; DMSO = dimethylsulfoxide), have been synthesized, of which 1 and 2 were structurally characterized by single-crystal X-ray diffraction. These compounds crystallize in the monoclinic space group P21/n with a =17.849(4) A, b = 9.6537(19) A, c = 23.127(5) A, beta = 109.06(3) degrees , and V = 3766.5(13) A3 for 1 and a =17.809(4) A, b = 9.6548(19) A, c = 23.075(5) A, beta = 108.97(3) degrees , and V = 3752.1(13) A3 for 2. The crystal structures of 1 and 2 consist of homodinuclear species that are bridged by two oxygen atoms from two carboxylate ligands. The two lanthanide ions are related by a center of inversion. Each lanthanide ion is coordinated by eight oxygen atoms in an overall distorted square-prismatic geometry. Six of the oxygen atoms are furnished by the carboxylate moieties, and the remaining two oxygen atoms are provided by water and DMSO molecules. The photophysical properties of these complexes in the solid state at room temperature have been investigated. The quantum yields were found to be 0.06 +/- 0.01 and 7.30 +/- 0.73% for 1 and 2, respectively.

The synthesis and X-ray crystal structures of the following bis(amidinate)-substituted boron halides are reported: 1,3-C6H4[C{N(SiMe3)}2BCl2]2 (3), 1,4-C6H4[C{N(SiMe3)}2BCl2]2 (4), 1,4-C6H4[C{N(SiMe3)}2B(Ph)Cl]2 (5), 1,4-C6H4[C{NCy}2BCl2]2 (6), and 1,4-C6H4[C{NCy}2B(Ph)Cl]2 (7). Compounds 3–5 were prepared by trimethylsilyl chloride elimination, while 6 and 7 were prepared via salt metathesis reactions of the appropriate dilithium bis(amidinates) with BCl3 or PhBCl2. The molecular structures of complexes 3, 5, and 6 were determined by single-crystal X-ray diffraction, along with that of the free bis(amidine) 1a.

Bis(imino)acenaphthene (BIAN) zinc complexes with para-substituted aryl groups have been synthesized and investigated from the standpoint of their photophysical properties. Each complex was found to be nonemissive in solution. However, complexes 1–6 turned out to be emissive in the solid state, while complexes 7 and 8 remained nonemissive. The emissions for complexes 1–8 displayed color tunability ranging from red-yellow. A detailed crystallographic study of the “as-synthesized” structures revealed a distinct difference in the crystal packing environments of the emissive and nonemissive complexes. Furthermore, a solvatomorphic study provided further emission tunability via changes in the crystal packing environments of each solvatomorph. Lastly, TD-DFT calculations were performed in order to investigate the effect of different para-substituents on the flanking aryl rings of the BIAN ligand.

A new stable crystalline carbene, 1,3-bis(1-adamantyl)benzimidazol-2-ylidene, was synthesized by decomposition of 1,3-bis(1-adamantyl)-2,3-dihydro-1H-benzimidazol-2-ylacetonitrile on heating under reduced pressure. Heteroaromatic 1,3-R2-disubstituted benzimidazol-2-ylidenes, both stable (R = 1-Ad) and generated in situ (R = Me, Bzl), as well as 1,3,4,5-tetraphenylimidazol-2-ylidene (generated in situ), reacted with acetonitrile to give the corresponding insertion products, 1,3-disubstituted 2-cyanomethyl-2,3-dihidro-1H-(benz)-imidazoles. The geometric parameters of 1,3-bis(1-adamantyl)benzimidazol-2-ylidene, determined by X-ray analysis, suggest its lower aromaticity as compared to imidazol-2-ylidenes and 1,2,4-triazol-5-ylidenes. The structures of 2-cyanomethyl-2,3-dihydro-1H-benzimidazoles, 2-cyanomethyl-1,3,4,5-tetraphenyl-2,3-dihydro-1H-imidazole, and 1-(1-adamantyl)-5-cyanomethyl-3,4-diphenyl-4,5-dihydro-1H-1,2,4-triazole are characterized by partial conjugation in the heteroring; some compounds exhibit luminescence under UV irradiation. 1,3-Bis(1-adamantyl)benzimidazol-2-ylidene reacted with molecular sulfur in benzene to give 1,3-bis-(1-adamantyl)-2,3-dihydro-1H-benzimidazole-2-thione, but it failed to react with selenium under analogous conditions.

The synthesis and X-ray crystal structures of the following amidinate-substituted boron halides are reported: [tBuC{N(Cy)}2]BCl(Ph) (1), [nBuC{NCy}2]BCl(Ph) (2), [(Me3Si)2NC{NCy}2]BCl2 (3) and [MeC{NiPr}2]BCl2 (4). Compounds 1, 2, and 3 were prepared via salt metathesis reactions of the appropriate lithium amidinates with PhBCl2 or BCl3. Compound 3 was also prepared by carbodiimide insertion into the B–N bond of (Me3Si)2N–BCl2. The latter method represents the first example of the insertion of a carbodiimide into a B–N moiety. The molecular structures of 1, 2, and 4 were determined by single-crystal X-ray diffraction.

The complex [Ti2Cl4(NNMe2)2(py)3] (1) has been prepared via the reaction of TiCl4 with LiN(H)NMe2, followed by treatment with pyridine. Preparation of the complex [TiCl(PhC{N(SiMe3)2}2)2(MeNNMe2)] (2) was carried out by treatment of TiCl4 with Li[PhC{N(SiMe3)2}]tmeda, followed by reaction with LiN(Me)NMe2. The structures of 1 and 2 were determined by single crystal X-ray diffraction. The single crystal X-ray structure of Li[PhC{N(SiMe3)2}]tmeda (3) has also been determined.

Trimethylaluminum reacts with 2,6-diaminopyridine in a 3:2 mole ratio to form the unusual cage-type compound AlMe[AlMe 2 {N(H),N(H)–C 5 H 3 N}] 2 ( 1 ). The structure of 1 , which was established by single crystal X-ray diffraction, features an overall bowl shape. The bowls stack along the (0 1 0) direction.

The β-aminoimine [HC(CMe)2(NC6F5)2]H (1) is readily converted into the lithium β-diketiminate [HC(CMe)2(NC6F5)2]Li·OEt2 (2) by treatment with MeLi. The aluminum and gallium derivatives [{HC(CMe)2(NC6F5)2}MMe2] (M = Al (3); Ga (4)) have been prepared via the CH4 elimination reactions of 1 with MMe3. The X-ray crystal structures of 1 - 4 have been determined and the trends in metrical parameters are discussed.

The ketiminate complex AlCl[OC(Me)CHC(Me)N(p-C6H4F)]2 (4) has been prepared from the β-aminoenone, O C(Me)CH C(Me)N(H)(p-C6H4F) (3) by lithiation of 3 with n-BuLi, followed by reaction with AlCl3 and by the reaction of 3 with Me2AlCl. A second compound, [AlCl2{O C(Me)CH C(Me)N(H)(p-C6H4F)}4][AlCl4] (5), was also isolated from the AlCl3 reaction. The structures of 4 and 5 were determined by X-ray diffraction analysis.

The triple-decker cation salts [(η 5 -C 5 Me 5 )M(μ-η 5 -C 5 Me 5 )M(η 5 -C 5 Me 5 )][B(C 6 F 5 ) 4 ] (M = Sn, Pb) have been prepared by treatment of [(η 5 -C 5 Me 5 )M][B(C 6 F 5 ) 4 ] with the corresponding metallocenes, [M(η 5 -C 5 Me 5 ) 2 ] (M = Sn, Pb). Investigation of the structures of these triple-decker systems by X-ray crystallography revealed an overall cis-type cationic geometry. In solution, NMR studies indicate that the triple-decker cations undergo rapid, reversible dissociation. The reaction of [In(η 5 -C 5 Me 5 )] with an equimolar quantity of H 2 O.B(C 6 F 5 ) 3 and B(C 6 F 5 ) 3 ] afforded [(η 6 -toluene)In(μ-η 5 -C 5 Me 5 )In(η 6 -toluene)][(C 6 F 5 ) 3 B(OH)B(C 6 F 5 ) 3 ]. Density functional theory calculations on a model system indicate that the capping toluene molecules in this di-indium cation are weakly bonded. Use of the smaller counter-ion [B(C 6 F 5 ) 4 ] - results in isolation of the inverse sandwich cation [In(μ-η 5 -C 5 Me 5 )In] + .

Donor–acceptor bonding between group 13 elements seems counter-intuitive because one normally thinks of e.g. boron and aluminium compounds as classical Lewis acids. Indeed, many such compounds have achieved industrial prominence in this regard. Recently, however, it has become possible to stabilize these and other group 13 elements in the +1 oxidation state as opposed to the archetypical +3 oxidation state. Moreover, it turns out that in the +1 oxidation state these species are excellent donors – hence the formation of these unprecedented donor–acceptor bonds. The discovery of such bonds has led, albeit indirectly, to the development of triple-decker main group cations. This aspect is also covered in the review.

Two new, more convenient methods for the synthesis of 1,2,4-triazol-5-ylidenes are described. Four new 1,2,4-triazol-5-ylidenes have been prepared using these methods: 1-(1-adamantyl)-3,4-diphenyl-1,2,4-triazol-5-ylidene (2a), 1-(1-adamantyl)-3-phenyl-4-(p-bromophenyl)-1,2,4-triazol-5-ylidene (2b), 1-(1-adamantyl)-3-phenyl-4-(alpha-naphthyl)-1,2,4-triazol-5-ylidene (2c), and 1-(1-adamantyl)-3,4-di(p-bromophenyl)-1,2,4-triazol-5-ylidene (2d). The X-ray crystal structures of 2d and the precursor salt 1-(1-adamantyl)-3,4-di(p-bromophenyl)-1,2,4-triazolium bromide (1e) are described. Compound 2a reacts with CH(3)CN via C-H insertion to form 1-(1-adamantyl)-3,4-diphenyl-5-cyanomethyl-5H-1,2,4-triazoline (3), and 2a and 2d react with elemental sulfur and elemental selenium, respectively, to form the corresponding thione (4) and selenone (5).

The reaction of 3,5-(CF 3 ) 2 PzLi with [Rh(COD)Cl] 2 , IrCl(CO) 3 , [PdCl(η 3 -C 3 H 5 )] 2 and PtCl 2 (COD) in diethylether solution at 0 °C results in the formation of [Rh(COD)(μ-3,5-(CF 3 ) 2 Pz)] 2 ( 1 ), [Ir(CO) 2 (μ-3,5-(CF 3 ) 2 Pz)] 2 ( 2 ), [Pd(η 3 -C 3 H 5 )(μ-3,5-(CF 3 ) 2 Pz)] 2 ( 3 ), and Pt(COD)(η 1 -3,5-(CF 3 ) 2 Pz) 2 ( 4 ), respectively (3,5-(CF 3 ) 2 Pz=3,5-(CF 3 ) 2 pyrazolate; COD=1,5-cyclooctadiene). Compounds 1 – 3 are dimeric with bridging 3,5-(CF 3 ) 2 Pz ligands while 4 is monomeric and features two η 1 -3,5-(CF 3 ) 2 Pz groups. All compounds have been characterized by spectroscopic methods and their X-ray crystal structures have also been determined.

The chloropnictines (η-C5Me5)2AsCl (1), (η-C5Me5)2SbCl (2), and (η-C5Me5)2BiCl (3) have been prepared by treatment of the appropriate element trichloride with LiC5Me5. X-ray crystallographic assays establish that in the case of 1, both C5Me5 rings are attached to As in an η1(σ) fashion. In 2 and 3, the C5Me5 rings are π delocalized and feature tri- and pentahapto ring binding, respectively, to the group 15 element. Conversion of 1 and 2 to the salts [As(η-C5Me5)2][AlCl4] (4) and [Sb(η-C5Me5)2][AlCl4] (5) was effected by reaction with the stoichiometric quantity of Al2Cl6. The X-ray crystal structure of 4 is surprisingly complex and features four independent ion pairs in the asymmetric unit with a variety of hapticities for the π-bonded C5Me5 rings. The structure of the stibocenium cation of 5 involves bis(η4) attachment of the π-bonded C5Me5 rings.Key words: main group metallocenes, arsocenium cations, stibocenium cations, group 15 pentamethylcyclopentadienyl chlorides.

Solid-state NMR experiments, analytical and numerical simulations of solid NMR powder patterns, ab initio self-consistent field and hybrid density functional theory calculations, and single-crystal X-ray diffraction are used to characterize the molecular structure and anisotropic NMR interaction tensors in the bis(pentamethylcyclopentadienyl)aluminum cation, [Cp(2)Al](+). This highly symmetric main group metallocene has a structure analogous to that of ferrocene and the cobaltocenium cation. The single-crystal X-ray diffraction structure is reported for [Cp(2)Al][AlCl(4)]. Solid-state (27)Al[(1)H] magic-angle spinning and static NMR experiments are used to study the aluminum chemical shielding and electric field gradient tensors, revealing axial symmetry in both cases with a large chemical shielding span of Omega = 83(3) ppm and a small nuclear quadrupole coupling constant, C(Q)((27)Al) = 0.86(10) MHz. Carbon-13 CPMAS NMR experiments in combination with ab initio calculations and simulations of the effects of chemical exchange on (13)C static powder patterns reveal dynamic rotation of rings and suggest a low internal rotational barrier for this process. Theoretical computations of interaction tensors using the Gaussian 98 and Amsterdam Density Functional software packages are in good agreement with experiment and lend insight into the molecular origin of these NMR interactions. Orientations of the NMR tensors determined from theory, the large chemical shielding span, and the very small value of C(Q)((27)Al) can all be rationalized in terms of the high molecular symmetry.

Solid-state double-resonance and triple-resonance 13C, 11B, and 1H NMR experiments are used to investigate two main group metallocene complexes: the decamethylcyclopentadienylborinium cation, [Cp*2B]+, and bis(pentamethylcyclopentadienyl)methylborane, Cp*2BMe. The crystal structure for the latter complex is reported herein. A combination of magic-angle-spinning and static 11B{1H} NMR experiments are used to measure 11B nuclear quadrupole coupling constants (CQ) and rare instances of anisotropic boron chemical shielding tensors. Boron-11 nuclear quadrupole coupling constants reflect the higher spherical symmetry of [Cp*2B]+ compared to Cp*2BMe, with CQ(11B) = 1.14 MHz in the former and CQ(11B) = 4.52 MHz in the latter. Chemical shielding tensor spans are measured for [Cp*2B]+ and Cp*2BMe as Ω = 73.0 and 146.0 ppm, respectively. Hartree−Fock and hybrid density functional theory (B3LYP) calculations of electric field gradient and chemical shielding tensors are in quantitative agreement with experiment, and ...

The differences in redox behavior of the monofunctional bis(imino)acenaphthene (BIAN) and bifunctional tetrakis(imino)pyracene (TIP) ligands have been explored by treatment of the latter with PI(3), TeI(4), or BI(3). These reactions result in the formation of products involving the transfer of three or four electrons. Accompanying DFT calculations reveal that in each case the extent of electron transfer from each p-block element into the TIP ligand is dependent upon the element-TIP bonding interactions.

We report the synthesis and catalytic activity of a polymeric imidazolium salt. In contrast to the well-known resin-supported N-heterocyclic carbenes (NHCs), the material described herein affords a polymer with NHCs orthogonally positioned along a main chain upon generation in situ. The unique structural characteristics of the corresponding poly(NHC)s enabled the materials to display catalytic activities that were similar or superior to those displayed by monomeric analogues. Moreover, the new catalyst was successfully recovered and reused with minimal loss of performance over several cycles.

A new sterically shielded carbene with branched aromatic substituents (9a) and two palladium halogenide complexes (11a,b) have been prepared. The single crystal X-ray structures of free carbene 9a and palladium carbene complexes 10b and 11a were determined. Very high catalytic efficiencies were evident for the sterically shielded palladium carbene complexes 10b and 11a,b when the latter complexes were employed as catalysts for hydrodechlorination of the chloroarenes p-dichlorobenzene and hexachlorobenzene. When optimized, the foregoing approach is significantly more effective than those of currently known transition metal carbene complexes. The most active catalysts were found to be the monocarbene complexes of palladium chloride and iodide, both of which feature highly branched aromatic substituents (11a,b).

The new sterically shielded 1,3,4-trisubstituted 1,2,4-triazol-5-ylidenes 8b–d were synthesized by a three step method starting from 2-phenyl-1,3,4-oxadiazole. The syntheses of palladium complexes 9a–d and 10a–d (including the sterically shielded derivatives 9c,d and 10a–d) were carried out via the reactions of the stable carbenes 8a–d with palladium halogenide salts in THF or toluene solution. Complexes 9c,d and 10a–d were found to be excellent catalysts for the reductive dechlorination (hydrodechlorination) of p-dichlorobenzene. The structures of 8c, 9a,b, and 10a were determined by single-crystal X-ray diffraction.

The molecular structures of the stable phosphinyl and arsinyl radicals, •PnR2 [Pn = P (2); As (4); R = CH(SiMe3)2], have been determined by gas-phase electron diffraction (GED) in conjunction with ab initio molecular orbital calculations. The X-ray crystal structures of the corresponding dipnictines, the “dimers”, R2PnPnR2 [Pn = P (1), As (3)], and the chloro derivatives R2PnCl [Pn = P (5), As (6)] have also been determined. Collectively, these structural investigations demonstrate that large distortions of the ligands attached to Pn occur when the pnictinyl radicals unite to form the corresponding dipnictine dimers. Principally, it is the shape and flexibility of the CH(SiMe3)2 ligands that permit the formation of the P−P and As−As bonds in 1 and 3, respectively. However, theoretical studies indicate that in the process of pnictinyl radical dimerization to form 1 and 3, both molecules accumulate substantial amounts of potential energy and are thus primed to spring apart upon release from the solid state ...

Direct liquid injection chemical vapor deposition of (Al,Ti)N films using NH3 and a solution of tetrakis(dimethylamino)titanium and the tris(dimethylamino)alane dimer in toluene is reported. The decomposition reactions of the dimethylamino-based precursors with and without the presence of NH3 are studied to explain the incorporation of Al, Ti, N and C into the (Al,Ti)N films. Addition of NH3 during pyrolysis decreases the decomposition temperature of both precursors by more than 90 K. (Al,Ti)N films containing Al, Ti, N, C and O were deposited on a SiO2 substrate between 425 and 625 K. Introducing 0.002 torr of NH3 increased the film growth rate nearly 20 times and reduced the carbon content in half at 550 K; carbon was reduced as low as 5 at.% at 425 K. The addition of 0.002 torr NH3 also reduced the Al/Ti ratio by more than 62% and resulted in nearly 45% more N incorporation at all film growth temperatures. A 10-fold increase in the aluminum precursor partial pressure resulted in a 60% increase in film aluminum concentration. The films were not resistant to oxidation; exposure to ambient resulted in 330% more oxygen in the film and the removal more than 40% of the carbon and nitrogen from the (Al,Ti)N film. Conformal (step coverage near unity) (Al,Ti)N films were produced in 0.18 μm SiO2 trenches with an aspect ratio of five at 425 K in the presence of NH3 and at 550 K without NH3.