Jian-Fang Chai

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 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 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.

Tetranuclear heterodimetallic metallamacrocyles with M-Sn(IV) (M = Mo or W) bonds. Crystal structures of {p-[(CO)3MoC5H4C(O)]2C6H4} {(Ph2Sn)2S} and {p-[(CO)3MoC5H4C(O)]2C6H4} {(Ph2Sn)2CH2}

Abstract The dianions {[ p -(CO) 3 MC 5 H 4 C(O)] 2 C 6 H 4 } 2− reacted with Ph 2 SnBr 2 in a 1:2 or 1:1 ratio to give tetranuclear heterodimetallic complexes p -[(Ph 2 BrSn)(CO) 3 MC 5 H 4 C(O)] 2 C 6 H 4 (M=Mo ( 1 ) or W ( 2 ), respectively), and with CH 2 (SnPhBr 2 ) 2 to yield tetranuclear heterodimetallic metallamacrocycles { p -[(CO) 3 MC 5 H 4 C(O)] 2 C 6 H 4 }{(Ph 2− n Br n Sn) 2 CH 2 } ( n =1, M=Mo ( 5 ) and W ( 6 ); n =0, M=Mo ( 7 ) and W ( 8 ), respectively). Only one bromide on the tin atom was replaced by the metallic anions owing to the electron-withdrawing groups on the cyclopentadienyl rings greatly decreasing the nucleophilicity of the metallic anions. Treatment of complexes 1 and 2 with Na 2 S·9H 2 O yielded the novel metallamacrocyclic complexes { p -[(CO) 3 MC 5 H 4 C(O)] 2 C 6 H 4 }{(Ph 2 Sn) 2 S} (M=Mo ( 3 ) and W ( 4 ), respectively). All compounds have been characterized by elemental analyses, IR and 1 H-NMR spectra. The crystal structures of complexes 3 and 7 determined by X-ray crystallography indicate a novel 14-membered organometallic metallamacrocyclic ring system in which two Mo–Sn units are linked by the bridging cyclopentadienyl ligand and the sulfur or carbon atom. In addition, the carbonyl group π-system is coplanar with the adjacent cyclopentadienyl ring system, but markedly deviates from the bridging phenyl plane.

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).

Bridging cyclopentadienyl MSn(IV) bonded polymetallic complexes: X-ray crystal structures of [(Me2SnCl)(CO)3MoC5H4C(O)CH2]2·CH2Cl2 and [(Ph3Sn)(CO)3WC5H4C(O)CH2]2·3H2O

Abstract The dianions [(CO)3MC5H4C(O)CH2]2xa02− reacted with RnSnX4−n in a 1:2 or 1:1 ratio to give tetranuclear complexes [(RnSnX3−n)(CO)3MC5H4C(O)CH2]2 (M=Mo or W; R=Ph or Me; X=Cl or Br; n=2 or 3), which have been characterized by elemental analysis, 1H NMR and IR spectroscopy. The electron-withdrawing groups on the cyclopentadienyl rings greatly decrease the nucleophilicity of the metallic anions. Thus, only one halogen atom on tin was replaced by the metallic anion when the dianions reacted with SnR2X2. The crystal structures of complexes 4 (M=Mo; R=Me; X=Cl; n=2) and 5 (M=W; R=Ph; n=3) were determined by X-ray crystallography, indicating that both Mo and W atoms adopt a 3:4 piano stool structure, and the Snue5f8M bond length is 2.7755(3) A in complex 4 (Snue5f8Mo) and 2.8154(7) A in complex 5 (Snue5f8W).

Synthesis, crystal structure and electrochemical properties of carbonylchromium and tungsten complexes containing substituted pyrazole ligands

A series of carbonylchromium and tungsten complexes containing substituted pyrazole ligands, M(CO)5L, have been synthesized by the photochemical reactions of substituted pyrazoles with M(CO)6 (M = Cr or W). Their electrochemical behavior, investigated by cyclic voltammetry, indicates that the chromium complexes exhibit one reversible or quasi-reversible couple corresponding to a one-electron oxidation, whereas the tungsten complexes have one irreversible oxidation process. The crystal structure of W(CO)5L [L = 3(5)-t-butylpyrazole] was determined by X-ray diffraction, indicating that 3(5)-t-butylpyrazole is a monodentate ligand, and that the central metal is six-coordinate with a quasi-octahedral coordination geometry. All new compounds were characterized by elemental analyses, i.r., 1H-n.m.r. and by 13C-n.m.r. in the case of the tungsten complexes.