Xue-Bing Leng

Synthesis and reactivity of Group 6 metal carbonyl complexes containing bis(triazol-1-yl)methane: linkage coordination polymers

Abstract The reaction of bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane, CH2(3,5-Me2Tz)2, with M(CO)6 (M=Cr, Mo or W) in refluxing DME produces CH2(3,5-Me2Tz)2M(CO)4 in moderate yield. The crystal structures determined by X-ray analysis show that bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane acts as a chelating bidentate ligand with two endodentate nitrogen atoms in these complexes. Reactions of complexes CH2(3,5-Me2Tz)2M(CO)4 (M=Mo or W) with R2SnX2 (R=Ph or Me; X=Cl or Br) in a 1:1 or 1:2 ratio, respectively, only yield 1:1 adducts. In these adducts, bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane may coordinate to tin atom through exodentate nitrogen atoms on the 4-position of triazole rings to form linkage coordination polymers. Possibly owing to weak donors of 4-position exonitrogen atoms on triazole rings to organotin acceptors, the dissociation of these adducts in solution could exist. Adduct of CH2(3,5-Me2Tz)2W(CO)4·SnPh2Br2 absorbs one water molecule while crystals are growing and becomes the hydrolysis product [SnPh2Br2(H2O)]·(CH2(3,5-Me2Tz)2W(CO)4), which is characterized by X-ray crystallography, indicating that tin atom is five coordinate with a trigonal bipyramid geometry, the water molecule coordinates to the tin atom, and is simultaneously connected to the exonitrogen atoms on the 4-position of triazole rings of two adjacent CH2(3,5-Me2Tz)2W(CO)4 units through hydrogen bonds to form linkage coordination polymers, in which two coordination modes are observed.

Three-dimensional frameworks built from hydrogen bonds and π–π stacking interactions: structural and spectral study on Co(II) complexes of 1,5-diazacyclooctane (DACO) functionalized by heterocyclic pendants

Abstract A series of penta-coordinated Co(II) complexes of 1,5-diazacyclooctane (DACO) functionalized by additional imidazole or pyridine donor pendants, [CoL1Cl](ClO4)·H2O (1), [CoL2Cl](ClO4) (2) and [CoL3Cl](ClO4) (3), where L1=1,5-bis(imidazole-4-ylmethyl)-DACO, L2=1,5-bis(N-1-methylimidazol-2-ylmethyl)-DACO and L3=1,5-bis(pyridyl-2-ylmethyl)-DACO, have been synthesized and characterized by IR spectra, elemental analyses, conductance, thermal analyses and UV–Vis techniques. The structures of complexes 1 and 2 have been determined by X-ray crystallography. In all the mononuclear complexes, each Co(II) center is penta-coordinated due to the boat/chair configuration of the DACO rings and quite stable to oxidation. The most striking feature of complexes 1 and 2 is the formation of different 3D networks with channels through hydrogen-bonding and π–π stacking interaction. The solution behaviors of all the complexes have been further analyzed in detail.

Synthesis, structure and characterization of MSn (M=Mo, W) bonded heterobimetallic complexes containing bis(pyrazol-1-yl)methane ligands

Abstract The reaction of bis(pyrazol-1-yl)methane tetracarbonylmolybdenum(0) or tungsten(0) complexes with RSnCl3 (R=Ph, Cl) at room temperature yielded heterobimetallic complexes CH2(Pz)2M(CO)3(Cl)(SnCl2R) (Pz represents substituted pyrazole; M=Mo or W; R=Ph or Cl) in good yields, which have been characterized by elemental analysis, 1H NMR and IR spectroscopy. The reaction of bis(3,5-dimethyl-4-halopyrazol-1-yl)methane tetracarbonyl tungsten with PhSnCl3 did not take place even in refluxing CH2Cl2. The electronic and steric characteristics of substituents on the pyrazole ring remarkably influence the structures of the products. The structures of CH2(3,5-Me2-4-BrPz)2W(CO)3(Cl)(SnCl3) (8) and CH2(4-BrPz)2Mo(CO)3(μ-Cl)(SnCl2Ph) (17) (Pz: pyrazole) determined by X-ray crystallography show that no chlorine-bridged Wue5f8Sn bond is observed in complex 8, while one chlorine-bridged Moue5f8Sn bond exists in complex 17. The Snue5f8M bond length is 2.7438(5) A in complex 8 (Wue5f8Sn) and 2.7559(4) A in complex 17 (Moue5f8Sn).

A novel three-dimensional copper(II) network via hydrogen bonds: diaquabis[bis(pyrazol-1-yl-κN2)methane]copper(II) diperchlorate

The crystal structure of the title complex, [Cu(C7H8N4)2(H2O)2](ClO4)2, consists of a discrete centrosymmetric [Cu(C7H8N4)2(H2O)2]2+ cation and two perchlorate anions. The CuII centre is six-coordinated by four N donors from the two pyrazole rings [Cu—N 1.998u2005(2) and 2.032u2005(3)u2005A] and two O atoms from the water molxadecules occupying the apical sites [Cu—O 2.459u2005(3)u2005A]. The coordination geometry of the complex can be described as octahedral. There is a unique three-dimensional network in which the perchlorate units are linked by a combination of strong O—H⋯O and weak C—H⋯O hydrogen bonds.

5,6-Bis(2-pyridyl)-2,3-pyrazine­dicarbo­nitrile

The crystal structure of the title compound, C16H8N6, contains two independent molxadecules with no significant difference in their structures. The pyrazine ring makes dihedral angles of 36.7u2005(2) and 36.5u2005(3)° with the two pyridine rings in one molxadecule, and 43.1u2005(2) and 38.4u2005(1)° in the other. The dihedral angles between the two pyridine rings are 58.2u2005(2) and 56.0u2005(2)°, respectively. The favoured orientation of the pyridine rings is such that their N atoms face each other.

[1,5-Bis(1-methyl-1H-imidazol-2-yl­methyl-κN3)-1,5-di­aza­cyclo­octane-N,N′]chlorocobalt(II) perchlorate

The crystal structure of the title compound, [CoCl-(C16H26N6)]ClO4, consists of discrete [CoClxad(C16xadH26N6)]+ cations and perchlorate anions. The five-coordinate CoII atom has four nitroxadgen donors from the new mesocyclic ligand 1,5-bis(1-methyl-1H-xadimidazol-2-ylmethyl)-1,5-dixadazaxadcycloxadoctane [Co—N 2.046u2005(3)–2.214u2005(4)u2005A], and a chloride anion at the apical site [Co—Cl 2.3184u2005(13)u2005A]. The coordination geometry of the complex is essentially square pyramidal. The mesocyclic ligand takes a boat–chair configuration and the two imidazole pendants are not coplanar. The dihedral angle between the two imidazole planes is 15.97°. An H atom from the 1,5-diazaxadcycloxadoctane group effectively blocks the axial coordination site opposite the Cl ligand.

Chloro(2-{[5-(2-hydroxy­benzyl-O)-1,5-di­aza-1-cyclo­octyl-N,N′]­methyl}phenolato-O)­cadmium(II)

The crystal structure of the title complex, [Cd(C20H25xadN2xadO2)xadCl], reveals a hydrogen-bonded dimer composed of neutral molecules. The CdII center is five-coordinated by two O atoms of the pendant arms, two nitroxadgen donors of the 1,5-dixadazaxadcycloxadoctane ring and a chloride anion. The coordination geometry of the complex could be described as a distorted square pyramid. The 1,5-dixadazaxadcycloxadoctane backbone adopts a boat/chair configuration and the two phenol/phenolato groups have a dihedral angle of 101.3u2005(2)° between them. The coordinated phenolate and phenolic groups of inversion-related molxadecules form strong intermolecular O—H⋯O hydrogen bonds.

Di­azido­[bis(2‐pyridyl)­amine‐N,N′]­cobalt(III) perchlorate

The title complex, [Co(C10H9N3)2(N3)2]ClO4, consists of discrete cations and anions. The central CoIII ion has an approximate octahedral geometry, coordinated with four N atoms of the pyridine rings of the bis(2-pyridyl)xadamine ligands in a trans–trans mode, and with two terminal N atoms of the azide anions. The crystal structure is stabilized by N—H⋯O hydrogen bonds between the amino groups and the perchlorate anions.

r-1,c-2,t-3,t-4-1,3-Bis(4-methoxy­phenyl)-2,4-bis(5-phenyl-1,3,4-oxa­diazol-2-yl)­cyclo­butane 1,4-dioxane solvate

The asymmetric unit of the crystal structure of C34H28N4O4.C4H8O2, which is a 1:1 inclusion complex, consists of half a molxadecule of the title compound t-DPC and half a molxadecule of 1,4-dioxane. The structure shows that t-DPC is centrosymmetric; its cycloxadbutane ring has an exactly planar conformation, and is nearly square. The four C—C single bonds are of equal length [1.569u2005(4)u2005A] and the bond angles are 91.6u2005(2) and 88.4u2005(2)°. The major photodimerization process is a head-to-tail reaction rather than a head-to-head one.

Redetermination of [bis(2-pyridyl)­amine-N,N′]copper(II) diperchlorate

In the crystal structure of the title complex, [Cu(C10H9N3)2](ClO4)2, the CuII center is four-coordinated by the nitroxadgen donors of the pyridine rings of the ligand, bis(2-pyridyl)xadamine. The crystal structure reveals that the CuN4 coordination sphere has a distorted tetrahedral coordination geometry with a crystallographic C2 axis through the CuII center. The perchlorate anions link the complex cations to form a chain structure through C—H⋯O close contacts and N—H⋯O hydrogen bonds.