A series of new bis (pyrazol-1-yl) methanes with organotin groups on the methine carbon have been synthesized by the reaction of bis (pyrazol-1-yl) methyllithium with organotin halide. Their reactions with W (CO) 5THF have been investigated in detail, indicating that these new ligands display versatile reactivities upon treatment with W(CO)5THF, depending on the properties of the substituents on the tin atom. Treatment of triarylstannylbis(pyrazol-1-yl)methanes, Ar3SnCHPz2 (Ar) phenyl or p-tolyl; Pz) substituted pyrazole), with W(CO)5THF results in the oxidative addition of the tin-carbon(sp3) bond to the tungsten (0) center to yield novel metal-metal bonded complexes CHPz2(CO)3W-SnAr3, in which ourmembered metallacycles are found and bis (pyrazol-1-yl) methide acts as a tridentate monoanionic 3-[N,C,N] chelating ligand. When there are alkyl substituents in the 4-position of pyrazole rings, some decarbonylation intermediates Ar3SnCHPz2W (CO) 4 can be isolated. Sequentially heating these intermediates can also result in the oxidative addition of the tin-carbon (sp3) bond to the tungsten (0) center, implying that the oxidative addition reaction of the tin-carbon(sp3) bond may form these decarbonylation intermediates. While the reactions of trialkylstannylbis (pyrazol-1-yl) methanes, R3SnCHPz2 (R) Et or iPr), with W (CO) 5THF yield only the decarbonylation heterodinuclear complexes R3SnCHPz2W(CO)4, in which bis(pyrazol-1-yl)methanes act as N,N-chelating bidentate ligands, no analogous oxidative addition products are obtained. However, treatment of phenyldi(tert-butyl)-stannylbis (pyrazol-1-yl) methanes, (tBu) 2PhSnCHPz2 (Pz) 3,5-dimethylpyrazole or 3, 4, 5-trimethylpyrazole), with W (CO) 5THF results in the oxidative addition of the tin-carbon (sp2) bond instead of the tin-carbon (sp3) bond to the tungsten(0) center to yield metal-metal bonded complexes (tBu)2SnCHPz2W(CO)3(Ph), in which a novel 3-[N,Sn,N] coordination mode as well as asymmetric semibridging carbonyl between the W-Sn bond is observed. In addition, the reactions of trivinylstannylbis (pyrazol-1-yl) methanes, (CH2dCH) 3SnCHPz2, with W(CO)5THF result in a vinyl group bonded to the tungsten center in

ngsten complexeshave one reversible couple corresponding to the ferrocenyl group and one irreversible oxidation process for the molybdenum ortungsten center. The crystal structures of 3-ferrocenylpyrazole pentacarbonyltungsten (3) and 3-methyl-5-ferrocenylpyrazolepentacarbonyltungsten (6) are determined by X-ray diffraction method, indicating that both 3(5)-ferrocenylpyrazole and3(5)-methyl-5(3)-ferrocenylpyrazole act as a monodentate ligand, and the central metal of W is six-coordinate with a quasi-octahedralcoordination geometry in both complexes. Complex 3 is linked into a one-dimensional chain in solid through intermolecularhydrogen bonds formed by metal carbonyl as hydrogen bond acceptors, while complex 6 forms a dimer by similarintermolecular 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 tungstencomplexes have also been determined.

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 refluxingDME produces CH2 (3,5-Me2Tz) 2M (CO) 4 in moderate yield. The crystal structures determined by X-ray analysis show thatbis (3,5-dimethyl-1,2,4-triazol-1-yl) methane acts as a chelating bidentate ligand with two endodentate nitrogen atoms in thesecomplexes. 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 a1:1 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 coordinateto tin atom through exodentate nitrogen atoms on the 4-position of triazole rings to form linkage coordination polymers. Possiblyowing to weak donors of 4-position exonitrogen atoms on triazole rings to organotin acceptors, the dissociation of these adductsin solution could exist. Adduct of CH2 (3,5-Me2Tz) 2W (CO) 4

The reaction of 3 (5)-methylthio-5 (3)-phenylpyrazole with dibromomethane under phase-transfer catalytic conditions onlyaffords a new ligand, bis (3-phenyl-5-methylthiopyrazol-1-yl) methane. However, the reaction of 3 (5)-methylthio-5 (3)-pmethoxyphenylpyrazoleor 3 (5)-methylthio-5 (3)-tert-butylpyrazole with dibromomethane under the same conditions yields threeisomers, respectively, indicating that the substituents significantly affect the steric and electronic properties of pyrazole ring duringthe formation of ligands. Treatment of these potential polydentate ligands with M (CO) 6 (M=Cr, MoorW) under UV irradiationat room temperature affords (NN) 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 thecoordination to the metal centers, and S-rich bis (pyrazol-1-yl) methanes actually act as bidentate chelating ligands by two nitrogenatoms. It is also interesting that in order to reduce the repulsion of methyl groups with carbonyls, the methyl groups in thesecomplexes are oriented away from the metal centers.

A series of new bis (pyrazol-1-yl)methane ligands with organogermyl and organosilyl groups on the methine carbon, MCHPz2(M/Ph3Ge, PhMe2Si, iPr3Si or Me3Si; Pz/3,5-dimethylpyrazole or 3,4,5-trimethylpyrazole), have been prepared by the reactionof bis (pyrazol-1-yl) methyllithium with triphenylgermanium bromide and organosilyl chloride. Treatment of these ligands withW (CO) 5 (THF) in refluxing THF resulted in new heterobimetallic complexes MCHPz2W (CO) 4 as major products, accompanied bypartial decomposition of ligands to yield a certain amount of PzW (CO) 5as by-products. These new ligands and complexes have beencharacterized by 1H-NMR, IR and elemental analysis. The molecular structures of complexes Ph3GeCHPz2W (CO) 4andMe3SiCHPz2W (CO)4 (Pz/3,5-dimethylpyrazole) have been determined by X-ray structure analysis, indicating that bis (pyrazol-1-yl)methanes act as chelating bidentate ligands in these complexes, and organometallic groups lie in the axial position of themethine carbon. # 2002 Elsevier Science B. V. All rights reserved.

The dianions {[p-(CO)3MC5H4C(O)]2C6H4}2 reacted with Ph2SnBr2 in a 1:2 or 1:1 ratio to give tetranuclear heterodimetalliccomplexes p-[(Ph2BrSn)(CO)3MC5H4C(O)]2C6H4 (M/Mo (1) or W (2), respectively), and with CH2(SnPhBr2)2 to yieldtetranuclear heterodimetallic metallamacrocycles {p-[(CO)3MC5H4C(O)]2C6H4}{(Ph2 nBrnSn)2CH2} (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 theelectron-withdrawing groups on the cyclopentadienyl rings greatly decreasing the nucleophilicity of the metallic anions. Treatmentof complexes 1 and 2 with Na2S/9H2O yielded the novel metallamacrocyclic complexes {p-[(CO)3MC5H4C(O)]2C6H4}{(Ph2Sn)2S}(M/Mo (3) and W (4), respectively). All compounds have been characterized by elemental analyses, IR and 1H-NMR spectra. Thecrystal structures of complexes 3 and 7 determined by X-ray crystallography indicate a novel 14-membered rganometallicmetallamacrocyclic ring system in which two Mo/Sn units are linked by the bridging cyclopentadienyl ligand and the sulfur orcarbon atom. In addition, the carbonyl group p-system is coplanar with the adjacent cyclopentadienyl ring system, but markedlydeviates from the bridging phenyl plane.

Treatment of triarylstannyl-bis (3,4,5-trimethylpyrazol-1-yl) methane, Ar3SnCH (3,4,5-Me3Pz)2 (Ar) phenyl or p-tolyl), with W (CO) 5THF results in the oxidative addition of the tin-carbon (sp3) bond to the tungsten (0) center to yield the heterodinuclear complexes CH (3,4,5-Me3Pz) 2 (CO) 3W-SnAr3, in which four-membered metallacycles are found and bis (3,4,5-trimethylpyrazol-1-yl) methide acts as a tridentate monoanionic 3-[N,C,N] chelating ligand. purity synthetic methods for poly (pyrazol-1-yl) alkanes have been explored. 5b, 7 In recent years, modification of the central carbon atom by the organic functional groups to form heteroscorpionate ligands has also been successful. These new heteroscorpionate ligands usually have asymmetric N2O, 8N2S, 9or N3O10 coordination environments. Recently, replacement of the central carbon atom by the silicon atom to form poly (pyrazol Poly (pyrazol-1-yl) alkanes were first reported to form transition-metal complexes by Trofimenko in 1970.1 After that, and especially after an improved synthetic method was developed by Julia et al.,2 the coordination chemistry of these ligands has received increasing attention. 3, 4 A number of main-group5 and transitionmetal6 complexes containing poly (pyrazol-1-yl) alkanes have been synthesized and characterized in recent years. To advance the development of poly (pyrazol-1-yl) alkane chemistry, some new higher yield and higher

Reaction of the dianion {p-[(CO)3MoC5H4C-(O)]2C6H4}2- with PhSnCl3 yields the tetranuclear heterodimetallic complex p-[(PhCl2Sn)(CO)3MoC5H4C-(O)]2C6H4 (1). Treatment of complex 1 with Na2S