Zhi-Hong Wang

Novel five- and six-coordinate diorganotin(IV) complexes with bis(triazol-1-yl)alkanes: linkage coordination polymers

Abstract A novel poly(triazol-1-yl)alkane ligand, bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane CH2(3,5-Me2Tz)2, has been synthesized under phase transfer catalytic conditions. This ligand as well as bis(1,2,4-triazol-1-yl)methane CH2Tz2 and 1,2-bis(1,2,4-triazol-1-yl)ethane (CH2)2Tz2 reacts with diphenyltin(IV) halides to yield novel five- and six-coordinate diorganotin complexes. The crystal structure of (CH2Tz2)SnPh2Br2 determined by X-ray analysis shows that bis(triazol-1-yl)methane coordinates to the tin atom through exodentate nitrogen atoms on the 4-position of triazole rings to form linkage coordination polymers, which leads to a bridging instead of a general chelating metal coordination. Possibly owing to the hindrance of methyl groups in the triazole ring of CH2(3,5-Me2Tz)2, this ligand is a weaker donor to an organotin acceptor than CH2Tz2. In the hydrolysis product [SnPh2Br2(H2O)]·(CH2(3,5-Me2Tz)2), the tin atom is five-coordinate with a trigonal bipyramid geometry, and the aqua ligand is simultaneously connected to the exonitrogen atoms of two adjacent CH2(3,5-Me2Tz) molecules through hydrogen bonding.

Synthesis of diorganotin derivatives containing asymmetric disubstituted bis(pyrazol-1-yl)methanes: X-ray crystal structures of (3-isopropylpyrazol-1-yl-5′-isopropylpyrazol-1-yl)methane diphenyltin(IV) dibromide and bis(5-isopropylpyrazol-1-yl)methane diphenyltin(IV) dibromide

Abstract The reaction of 3- tert -butylpyrazole with dibromomethane under phase-transfer catalytic conditions afforded a new ligand, bis(3- tert -butylpyrazol-1-yl)methane [CH 2 (3-Bu t Pz) 2 ]. However, the reaction of 3-isopropylpyrazole with dibromomethane under the same conditions yielded three isomers: bis(5-isopropylpyrazol-1-yl)methane [CH 2 (5-iPrPz) 2 ], (3-isopropylpyrazol-1-yl-5′-isopropylpyrazol-1-yl)methane [CH 2 (3-iPrPz-5′-iPrPz)] and bis(3-isopropylpyrazol-1-yl)methane [CH 2 (3-iPrPz) 2 ]. Although CH 2 (5-iPrPz) 2 suffered the greatest degree of steric hindrance, this ligand was obtained in highest yield. Upon treating the isomeric mixture with diorganotin halides in petroleum ether (60–90°C), the isomers were isolated in the form of diorganotin derivatives of bis(pyrazol-1-yl)methanes. The crystal structures of CH 2 (3-iPrPz-5′-iPrPz)SnPh 2 Br 2 and CH 2 (5-iPrPz) 2 SnPh 2 Br 2 determined by X-ray crystallography indicated that the isopropyl group in the 3-position of the pyrazole ring decreased the coordination ability of CH 2 (3-iPrPz-5′-iPrPz), and the average Sn–N distance in CH 2 (3-iPrPz-5′-iPrPz)SnPh 2 Br 2 (2.52 A) was longer than that in CH 2 (5-iPrPz) 2 SnPh 2 Br 2 (2.435 A).

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.

Synthesis, structures and electrochemical properties of Group 6 metal carbonyl complexes containing ferrocenylpyrazole ligands

Abstract A series of carbonylchromium, molybdenum and tungsten complexes containing ferrocenylpyrazole ligands, (M(CO)5L) (M=Cr, Mo or W; L represents ferrocenyl pyrazole), have been prepared by the photochemical reactions of ferrocenylpyrazole ligands with M(CO)6. Their electrochemical behaviors have also been investigated by cyclic voltammetry, indicating that chromium complexes exhibit two one-electron reversible or quasi-reversible couples, while molybdenum and tungsten complexes have one reversible couple corresponding to the ferrocenyl group and one irreversible oxidation process for the molybdenum or tungsten center. The crystal structures of 3-ferrocenylpyrazole pentacarbonyltungsten (3) and 3-methyl-5-ferrocenylpyrazole pentacarbonyltungsten (6) are determined by X-ray diffraction method, indicating that both 3(5)-ferrocenylpyrazole and 3(5)-methyl-5(3)-ferrocenylpyrazole act as a monodentate ligand, and the central metal of W is six-coordinate with a quasi-octahedral coordination geometry in both complexes. Complex 3 is linked into a one-dimensional chain in solid through intermolecular hydrogen bonds formed by metal carbonyl as hydrogen bond acceptors, while complex 6 forms a dimer by similar intermolecular hydrogen bond interactions. The N–H⋯O distances in complexes 3 and 6 are 2.932(11) and 2.900 A, respectively. All new compounds have been characterized by elemental analyses, IR, 1H-NMR. 13C-NMR spectra of molybdenum and tungsten complexes have also been determined.

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

Abstract 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 (Nue5f8N)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.

Synthesis, structures and electrochemical properties of VIB carbonyl complexes containing bis(4-halopyrazol-1-yl)alkanes

Abstract Bis(4-halopyrazol-1-yl)alkanes (1=bis(4-bromopyrazol-1-yl)methane CH2(4-BrPz)2, 2=bis(3,5-dimethyl-4-bromopyrazol-1-yl)methane CH2(3,5-Me2-4-BrPz)2, 3=bis(4-chloropyrazol-1-yl)methane CH2(4-ClPz)2, 4=bis(3,5-dimethyl-4-chloro-pyrazol-1-yl)methane CH2(3,5-Me2-4-ClPz)2) have been synthesized by the reaction of bis(pyrazol-1-yl)methane or bis(3,5-dimethylpyrazol-1-yl)methane with Br2 or SO2Cl2. These ligands react with M(CO)6 (M=Cr, Mo, W) to yield bis(4-halopyrazol-1-yl) methane tetracarbonyl chromium(0), molybdenum(0) and tungsten(0) complexes in reasonable yield. All new compounds have been characterized by elemental analyses, IR, 1H NMR and 13C NMR in the case of tungsten complexes. The electrochemical properties of these complexes studied by the cyclic voltammograms indicate that each compound exhibits one reversible or quasi-reversible couple corresponding to a one-electron oxidation. The structure of CH2(3,5-Me2-4-ClPz)2W(CO)4 determined by X-ray crystallography shows that the six-membered W–N–N–C–N–N metallacycle adopts a boat form.

Reaction of poly(pyrazol-1-yl)methane tetracarbonylmolybdenum (tungsten) with RSnCl3(R=Ph, Cl): X-ray crystal structure of CH2(3,5-Me2Pz)2W(Cl)(CO)3(SnCl3) (Pz:pyrazolyl)

Abstract Bis(pyrazolyl)methane can be synthesized by the reaction of pyrazole with dibromomethane in phase transfer catalytic conditions. It reacts with M(CO)6 (M=Mo, W) to give bis(pyrazolyl)methane tetracarbonylmolybdenum(0) and tungsten(0) complexes in good yield. Upon treatment of these complexes with RSnCl3 (R=Ph, Cl), the seven-coordinate Mo(II) and W(II) products were obtained. The molecular structure of CH2(3,5-Me2Pz)2W(Cl)(CO)3(SnCl3) determined by X-ray crystallography showed that the six-membered

Synthesis and crystal structure of a new two-dimensional chromium(III) network through hydrogen bonds

A new chromium(III) complex, [Cr(ox)(bdmpza)(H2O)], (ox = oxalate dianion and bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate, respectively), has been synthesized and characterized by X-ray crystallography. This compound crystallizes in the monoclinic space group P21/c, with a = 7.008(3) Å, b = 14.229(5) Å, c = 16.497(7) Å, β = 101.588(7)°, V = 1611.5(11) Å3, Z = 4. The chromium atom has a distorted octahedral environment with different coordination atoms. Bis(3,5-dimethylpyrazol-1-yl)acetate anion is a tridentate ligand, and the oxalate group acts as a chelating bidentate ligand. This compound also forms an infinite two-dimensional network through O–Hxa0⋅xa0⋅xa0⋅xa0O hydrogen bonds. The lengths of the hydrogen bonds are 2.765(5) and 2.733(5) Å, respectively.

Synthesis and reactivity of bis(3,5-dimethylpyrazol-1-yl)ethane tetracarbonylmolybdenum and tungsten X-ray crystal structureof bis(3,5-dimethylpyrazol-1-yl)ethane tetracarbonyltungsten

Bis(3,5-dimethylpyrazol-1-yl)ethane tetracarbonylmolybdenum (1a) and tungsten (1b) have been synthesized by the direct reaction of bis(3,5-dimethylpyrazolyl)ethane (bmpze) with M(CO)6 (M = Mo or W). The molecular structure (1b), determined by x-ray crystallography, showed the seven-membered ring W–N–N–C–C–N–N to be in the boat conformation. Upon treatment with RSnCl3 (R=Ph or Cl) in CH2Cl2 at room temperature, complexes (1a) and (1b) gave the seven-coordinate oxidative-addition products [(bmpze)M(CO)3(SnCl2R)Cl] [M = Mo, R = Ph, (2a); M = W, R=Ph, (2b); M = Mo, R = Cl, (2c); M = W, R = Cl, (2d)]. When complexes (1b) and (2b) were heated under reflux with 1,2-bis(diphenylphosphino)ethane (dppe), the ligand, bmpze, in these complexes was easily removed. The novel compounds were characterized by 1H-n.m.r., i.r. and elemental analysis.

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).