Suzuki Noriyuki

Mixed-ligand nickel(II) complexes Ni(acac)(dmap)X, [Ni(acac)(dmap)]BPh4 (1), [Ni(acac)(dmap)]BF4 (2), and [Ni(acac)(dmap)NO3] (3) (where acac = acetylacetonate and dmap = 1-dimethylamiiio-2-diphenylphosphinoethane) have been obtained for the first time and their X-ray single-crystal structures have also been determined. This series of complexes show different structures, hence colors, in the solid state depending on the coordination strength of the anion X-: the complexes with tetraphenylborate and tetrafluoroborate having no coordination ability are square-planar and orange, while on the contrary, the coordinating nitrate ligand produces an octahedral and pale blue complex. In solution, two types of solvatochromisin due to solute-solvent interaction and solute-solute-solvent interaction have been observed and these spectral behaviors are attributed to the changes in their geometries due to the donor/acceptor properties of the solvents. The thermochromic behavior of complex I has also been studied with temperature variation UV-vis spectra in various solvents. The behavior of these solvato- and thermo-chromisms of these complexes is due to the intermediate ligand field strength created by the dmap and the acac ligands.

A stable five-membered metallacycloalkyne 1 with alkylidene moieties was treated with an alkali metal to give a dianionic species 2, which was transformed into a 1-zirconacyclopent-3-ene complex by protonation. The alkylation of 2 afforded zirconocene-4-1,3-enyne complexes 3, which can be regarded as formal 1-zirconacyclopenta-2,3-dienes.

Nucleophilic reactions of 1,1-bis(eta(5)-cyclopentadienyl)-1-zirconacyclopent-3-yne (1) with proton and aldehydes were studied. The reaction with HCl gave a mixture of 2-butyne and 1,2-butadiene. Complex 1 reacted with benzaldehyde to give 1-phenyl-2-methyl-2,3-butadien-l-ol (3) in moderate yields in the presence of a proton source such as triethylammonium hydrochloride, while it gave 2-methylene-1-phenyl-3-buten-1-ol (4) on using triethylammonium tetraphenylborate. (c) 2007 Elsevier B.V. All rights reserved.

The title compound, (4-EtC6H4)(2)C = C = C = C = C = C(4-EtC6H4)(2) or C38H36, was prepared from 1,1,6,6-tetrakis(4-ethylphenyl)-2,4-hexadiyne-1,6-diol by reduction with SnCl2 in an acidic medium. The molecule has a centre of symmetry at the mid-point of the cumulative double bonds, in which longer and shorter bonds alternate.

Five-membered metallacyclic alkyne complexes of titanium and hafnium, 1,1-bis(cyclopentadienyl)-l-titanacyclopent-3-yne (2) and trans-1, 1-bis(cyclopentidienyl)-2,5-trimethylsilyl-1-hafiiacyclopent-3-yne (6), were synthesized and structurally characterized. The structural analysis of titanium complex 2 implied a larger contribution of an q(4)-pi,pi-coordinated structure. The hafnium compound 6 has a similar structure to the corresponding zirconium analogue (1a), although slight differences in the bond lengths and angles were observed. A novel 1-zirconacyclopent-3-yne complex, 1, 1-bis(methylcyclopentadienyl)-2,5-bis(trimethylsilyl)-1-zirconacyclopent-3-yne (5), was also prepared and the structure of the trans-isomer was determined. (c) 2005 Elsevier B.V. All rights reserved.

An electron density analysis of the 1-zirconacyclopent-3-yne complex has been carried out based on X-ray diffraction data, showing that the coordination mode of the but-2-yne-1,4-diyl ligand to the metal is a resonance hybrid between eta(2)-sigma, -coordination, as the major contributor, and eta(4)-pi, pi-coordination.

The ring-opening metathesis polymerization (ROMP) of norbornene catalyzed by bis(acetonitrile) molybdenum and tungsten complexes, [M(eta(3)-C3H5)Cl(CO)(2)(NCMe)(2)] (1-Mo: M=Mo, 1-W: M=W), which have two labile acetonitrile ligands. has been investigated. These complexes catalyzed the ROMP of norbornene as a single-component initiator. The highly vis-selective polymerization proceeded in a THF solution (95% for 1-Mo and 96% for 1-W), whereas polymerization in CH2Cl2 or toluene resulted in lower cis selectivity. The polymerization of terminal acetylenes using these complexes was also examined. The tungsten complex I-W showed a high catalytic activity for the polymerization of terminal acetylenes, such as phenyl- and tert-butylacetylene. A highly active catalytic system for the ROMP of norbornene was achieved by the activation of the tungsten complex, I-W, with one equivalent of phenylacetylene. giving poly(norbornene) with a high molecular weight (M-n = 391 x 10(4)) and a high cis selectivity (cis similar to 89%). (c) 2005 Elsevier B.V. All rights reserved.

A 1-zirconacyclopent-3-yne complex (1) reacted with "zirconocene" to give a symmetrical, bimetallic 1,2,3-butatriene complex (6) in which butatriene coordinates to two equivalent zirconocene units. Treatment of 6 with trimethylphosphine gave the phosphine-stabilized zirconocene-1 complex (2), which was transformed into 6 by addition of triethylborane.

The zirconocene-ethylene complex and (Z)S 1',4-bis(trimetlzylsilyl)-1,2,3-butatriene reacted to give a mixture of 1-zirconacyclopent-3-yne and 1-zirconacyclohept-3-yne. A zirconocene-alkyne complex gave, on the other hand, 1-zirconacyclohept-2-en-5-yne, which was structurally characterized as the major product along with a lesser amount of 1-zirconacyclopent-3-yne.

1-Titanacyclopent-3-yne and 1-hafnacyclopent-3-yne complexes were synthesized, and one of the titanium compounds was structurally characterized. Its molecular structure was similar to the zirconium analogue, although shorter Ti-C bonds may emphasize the ring strain of the five-membered cyclic alkyne structure.

Dehydrogenative dimerization of (Z)-1,4-bis(trimethylsilyl)-1,2,3-butatriene was catalyzed by Pd complexes in the presence of allyl halides to give predominantly an acyclic conjugated enyne, while addition of methylaluminoxane (MAO) instead of allyl halides produced an unprecedented dimer that has an alkynyl-substituted cyclopentadienyl structure.

A new family of highly active olefin polymerization catalysts based on titanium-tungsten heterobimetallic dinitrogen complexes, [Cp'TiCl2(mu-N-2)WCl(L)(4)] (1; L = PMe2Ph, 1/2 R2PCH2CH2PR2; R = Et, Ph), has been developed, in which the tungsten dinitrogen fragment acts as a novel metallonitrogen ligand to the catalytically active titanium center. Alkylation of 1d (Cp' = C5Me5, L = 1/2 Et2PCH2CH2PEt2) with MeLi gave di- and trimethyl derivatives 2d and 3d, which were structurally characterized.

Five-membered metallacyclic alkynes that have no substituents adjacent to the triple bond have been synthesized, isolated, and structurally characterized. Zirconocene dichlorides, Cp‘2ZrCl2 (Cp‘ = C5H5, C5H4-t-Bu), reacted with 1,4-dichlorobut-2-yne in the presence of magnesium to give 1-zirconacyclopent-3-yne compounds ((a) Cp‘ = C5H5, (b) Cp‘ = C5H4-t-Bu) that have a −CH2CCCH2− moiety in good yields. They are stable enough to be isolated in a pure form, despite the absence of substituents. 5a reacted with an equimolar amount of Cp2Zr(but-1-ene)(PMe3) to produce a bimetallic complex in which the zirconacyclopentyne coordinates to the other zirconocene moiety as an alkyne.

The 1,4-disubstituted butatrienes, (Z)-R-CH=C=C=CH-R (1, R = SiMe3, t-Bu), reacted with RhCl(PAr3)(3) (Ar = Ph, p-tolyl) to give rhodium-(Z)-butatriene complexes 3. The butatrienes coordinated to Rh with the central double bond in an eta(2)- fashion. (Z)-Butatrienes on 3 isomerized to (E)-form at 70 degreesC to afford (E)-butatriene complexes 4 with excellent E/Z ratios (E/Z = 97/3-99/1). The molecular structure of 4b (R = SiMe3, Ar = p-tolyl) was determined by X-ray diffraction analysis. Hydrosilation of I was catalyzed by rhodium complexes to give allenes as major products accompanied by 1,3-dienes as minor ones, which are results of 2,1-addition and 2,3-anti-addition of the silane.

The polymerization of 1-hexene under high pressures (100-750 MPa) was investigated with nickel-alpha-diimine complex/methylaluminoxane and palladium-alpha-diimine complex/methylaluminoxane as catalyst systems. The catalytic activity of both the nickel and palladium complexes monotonously increased as pressure rose and became two to four times higher than that observed at atmospheric pressure. Palladium catalysts gave poly(I-hexene)s with higher molecular weights under high pressure, whereas nickel-catalyzed high-pressure polymerizations gave polymers with higher molecular weights only at rather low monomer concentrations. The living-like character in the palladium-catalyzed polymerizations was somewhat enhanced under higher pressures, whereas the nickel-catalyzed polymerizations under high pressures were not living. More branches were found in the polymers produced by nickel catalysts at higher pressures. The chain-transfer reaction seemed to be accelerated by the high pressure in the nickel-catalyzed reactions, although this was not apparent in the palladium-catalyzed reactions. Dimers formed and were accompanied by high molecular weight polymers when nickel catalysts were used under high pressures and at high monomer concentrations. The possibility that very congested five-coordinated species act as key intermediates for the dimerization is discussed. (C) 2002 Wiley Periodicals, Inc.

Stable five-membered cyclic alkynes were synthesized, isolated, and fully characterized. Divalent zirconium species, bis(cyctopentadienyt)zirconium(II) equivalent, reacted with (Z)-1,4-disubstituted 1,2,3-butatrienes [(Z)-R-CH=C=C=CH-R, 1a: R = (CH(3))(3)Si-, 1b: R = tert-C(4)H(9)-] to give 1-zirconacyclopent-3-yne compounds (2a-b) in good yields. X-ray diffraction analysis revealed their five-membered cyclic structure with a sufficiently short triple bond to regard this compound as a metallacyclopentyne.

Novel methodology was developed for preparation of isospecific metallocene catalysts for olefin polymerization that are tethered on silica surfaces with covalent bonds. A racemic ansa-zirconocene complex that has a Si-Cl moiety on its bridge was immobilized on SiO2 by the reaction of the Si-Cl anchor with Si-OH on the solid surface, The prepared solid catalyst was found to be effective for isospecific propene polymerization (catalyst A). Pretreatment of silica surfaces with Me3SiCl improved the catalyst performance (catalyst B). An ansa-zirconocene complex with a BH group reacted with "vinyl-coated" silica gel to afford another immobilized catalysts (catalyst C). This catalyst achieved satisfactorily high catalytic activity and high isotacticity in its produced polypropene. (C) 2002 Elsevier Science B.V. All rights reserved.

In order to compare with silylene-bridged group 4 metallocenes, C-2 symmetric dimethylgermylene-bridged zirconocene and hafnocene dichlorides were prepared and employed as the catalyst for polymerization of propylene in combination with methylaluminoxane (MAO). Germylene-bridged metallocenes always produced isotactic polypropylene of higher molecular weight than that produced by silylene-bridged analogues. The molecular structures of four metallocenes prepared from dimethylsilylene and germylenebis(2,3,5-trimethylcyclopentadienyl) were detemined by X-ray diffraction and showed no substantial differences of geometry between silylene- and germylene-bridged ones.

A group 4 metallocene complex that serves as olefin polymerization catalyst was tethered on a solid support such as silica gel by covalent bonds. A zirconocene complex that has a vinyl group on its cyclopentadienyl ligand was hydrosilated or hydroborated to introduce a functional anchor for immobilization reactions. The complex with a Si-Cl group was tethered on a silica surface by the reaction with a surface Si-OH group. The zirconocene with a BH group was immobilized on a silica gel modified with chlorodimethylvinylsilane. Ethylene polymerization using the tethered catalysts, showed that the hydroboration-method seems more effective than the hydrosilation-method, It exhibited comparable catalytic activity to the corresponding homogeneous catalyst and produced polyethylene of a higher molecular weight.

The correlation between electron density at zirconium and catalytic activity in olefin polymerization was investigated with exclusion of any steric factors. Two novel Zr–Rh heterobimetallic complexes, meso-(η5-C9H7)- Rh{(η2-CH2

A zirconocene-ethylene complex reacted with propargylic ethers to give allene derivatives in good yields via beta-alkoxide elimination. Deuterolysis of the reaction mixture revealed that the final product after elimination still had a zirconium-carbon bond. Coupling of styrene and propargylic ethers was mediated by Cp2ZrBu2 (Negishi reagent) to give phenethyl allene derivatives. beta-Alkoxide elimination from zirconacyclopentadienes bearing two alpha-CH2OMe groups was also observed. One CH2OMe group was easily eliminated. Elimination of the second CH2OMe group was dependent on its structure. (C) 2000 Elsevier Science S.A. All rights reserved.

Polymerization of 1-hexene or 1-octene under high pressures (100-1000 MPa) was investigated using permethylated ansa-metallocenes/methylaluminoxane (MAO) as catalyst systems. Besides the known zirconocene complex (1, Me2Si(η5-C5Me4)2ZrCl2), dialkylsilyene- and dimethyl-germylene-bridged hafnocene dichlorides, R2E(η5-C5Me4)2HfCl2 (2, R = Me, E = Si 3, R = Et, E = Si 4, R = vinyl, E = Si 5, R = Me, E = Ge), were synthesized and structurally characterized. The catalytic activity of the ansa-metallocenes was remarkably enhanced under high pressures despite their very congested structures. Poly(1-hexene) with unprecedented high molecular weight such as Mw = 1.02 × 107 (Mw/Mn = 3.79, by GPC) was obtained under 750 MPa with 2. Studies on termination reactions revealed that the bimolecular chain-transfer process (β-hydrogen transfer to olefin) is much accelerated under 500 MPa in 1, while β-hydrogen elimination to metal is still major termination process in 2. This indicated that two complexes that have same structure but central metals showed quite different high-pressure effects.

A C-2-symmetric ansa-zirconocene complex which has a Si-Cl moiety on its bridge was immobilized on SiO2 by the reaction of the Si-Cl anchor with Si-OH on the solid surface. The prepared solid catalyst was found to be effective for isospecific propene polymerization. It exhibited higher productivity compared to a catalyst prepared using the zirconocene without a Si-Cl anchor. The effect of pretreatment of silica surfaces with Me3SiCl on catalyst performance is also described.

Novel heterobimetallic complexes that consist of zirconium and rhodium, LRh(eta(2)-CH2=CH)(2)Si(eta(5)-C5H2-2,4-Me-2)(2)ZrCl2 (3a L = eta(5)-C9H7, 3b eta(5)-C5H5, 3c eta(5)-C5Me5), were synthesized, and 3b was structurally characterized. The complexes have a "C-2-symmetric" ansa-zirconocene part and the rhodium metal on the bridge part. The complexes 3a-c in combination with methylaluminoxane catalyzed highly isospecific polymerization of a-olefins. Their catalytic activities were higher than that of the parent zirconocene complex, and the obtained polymer had a larger molecular weight.

Stereospecific polymerization of 1-hexene under high pressures (up to 1,000 MPa = ca. 10,000 atm) using metallocene/methylaluminoxane (MAO) catalysts was investigated. Several C-2-symmetric ansa-metallocenes, their meso-isomers, and two C-s-symmetric ansa-metallocenes were employed as catalyst precursors. In the course of this study, novel C-2-symmetric germylene-bridged ansa-metallocenes, (rac-[Me2Ge(eta(5)-C5H-2,3,5-Me-3)(2)MCl2] (M = Zr, rac-4a; M = Hf, rac-4b), have been prepared. High pressures induced enhancement of the catalytic activity and the molecular weight of the polymers in most of the catalysts. The maximum of both the catalytic activity and the molecular weight of the polymers was mostly observed at 100-500 MPa in each catalyst, although the enhanced ratio was smaller than that observed for nonbridged metallocenes. Isospecificity of the C-2-symmetric ansa-metallocene catalysts was essentially maintained even under high pressure. Highly isotactic polyhexene ([mmmm] = 91.6%) with very high molecular weight (M-w = 2,360,000) was achieved by rac-4b under 250 MPa. High pressures slightly decreased syndiotacticity when the C-s-symmetric ansa-metallocene, isopropylidene(1-eta(5)-cyclopentadienyl)(9-eta(5)-fluorenyl)zirconium dichloride 5, was employed. (C) 1999 John Wiley & Sons, Inc.

An ansa-zirconocene complex having a vicinally di-tert-butyl-substituted cyclopentadienyl ligand, Me2Si(C5H4)(C5H2-3,4-t-Bu-2)ZrCl2 (1), has been synthesized and characterized by X-ray diffraction (orthorhombic, space group: Pbca, a = 18.3690(8), b = 18.0749(12), c = 13.2039(9) Angstrom, V = 4383.9(4) Angstrom(3), Z = 8, R = 0.0283, R-w = 0.0291). Complex 1 has a very much twisted structure due to its steric repulsion. In solution, however, the two tert-butyl groups are magnetically equivalent even at -80 degrees C, indicating very fast oscillation of the bridged cyclopentadienyl unit with respect to the metal center. Complex 1 and nonbridged zirconocene dichlorides with tert-butyl-substituted cyclopentadienyl ligands, (C5H4-t-Bu)(2)ZrCl2 (2), (C5H3-1,2-t-Bu-2)(2)ZrCl2 (3) and (C5H3-1,3-t-Bu-2)(2)ZrCl2 (4), have been employed as methylaluminoxane (MAO)-activated catalysts for polymerization of 1-hexene under high pressure conditions (100-750 MPa = ca. 1000-7500 atm). Comparison with some non and methyl-substituted metallocenes are also discussed. (C) 1998 Elsevier Science S.A. All rights reserved.

Treatment of bis(phenylethynyl)silane (PhC=C)(2)SiR2 (R = Me (2a), Et (2b) or Ph (2c)) with Cp2ZrEt2 (1) (Cp = cyclopentadienyl) and H2O/CuCl in this order afforded (1E,3E)-1,4-diphenyl-1,3-butadiene (3) in 56-88% yields after hydrolysis. On the other hand, hydrolysis of the reaction mixture of 2a-h with Cp2ZrEt2 gave silacyclobutene derivatives 4a-h in 61-87% yields. Zirconium-containing intermediate 7 was obtained as crystals suitable for X-ray analysis when t-BuC5H4 was used as the ligands of a zirconocene derivative. Structure of 7 showed that the intermediate contained the zirconacyclobutene-silacyclobutene fused ring system. Reaction of silacyclobutene 4a with CuCl selectively opened the silacyclobutene ring. The further treatment of the reaction mixture with PhI in the presence of a catalytic amount of Pd(PPh3)(4) gave 1,3,4-triphenyl-1-silyl-1,3-butadiene compound 16. Zirconacyclopentadienes with an alkynylsilyl group at the alpha-position afforded zirconacyclohexadiene derivatives 19 in 82-98% yields. When t-BuC5H4 was used as the ligands instead of two Cp, the structure was determined by X-ray analysis. The structure clearly showed that 19 had the zirconacyclohexadiene-silacyclobutene fused ring system.

Ethylene and styrene derivatives reacted with various propargylic ethers in the presence of zirconocene(Ii) to afford allenic products in high yields. The reaction proceeded via formation of zirconacyclopentenes by selective coupling of an olefin and a propargylic ether, which was followed by beta-elimination of the siloxy group. Deuterolysis confirmed that the final product had a zirconium-carbon bond. (C) 1997 Elsevier Science Ltd.

The reaction of dilithiated silylene-bridged Cp-ligands, whose silylene had one or two vinyl substituents, with ZrCl4 gave raceme-rich mixtures of the complex RR'Si(C5H2-2,4-Me-2)(2)ZrCl2 (I: R = vinyl, R' = Me, rac/meso = 77/23, 4: R = R' = vinyl, rac/meso = 77/23). The pure racemic complex 1-rac was isolated after several recrystallization processes in a satisfactory yield (31%, rac/meso >99/1) and was structurally characterized. Polymerization of propylene with 1-rac/MAO gave highly isotactic polypropylene.

Selective monofunctionalization was investigated for symmetrical zirconacyclopentanes or symmetrical dialkylzirconocenes. Reaction of zirconacyclopentanes, which were prepared by intermolecular coupling of two alkenes, or intramolecular cyclization of dienes, trienes or tetraenes on zirconium, with PPh(2)Cl or SnR(3)Cl (R = Me, Ph) gave monofunctionalized products in good to high yields with high selectivities. Even in the presence of 2 equiv, of PPh(2)Cl or SnR(3)Cl, only one Zr-carbon bond reacted. Treatment of zirconacycropentanes with methanol yielded monoprotonated complexes. Subsequent addition of halogen such as Br-2 and I-2 to these monoprotonated complexes gave highly selective monohalogenated products. Similar monoprotonation reactions proceeded for dialkylzirconocene or -hafnocene complexes. Reaction of Cp(2)MR(2) (M = Zr or Hf, R = alkyl or aryl) with alcohols afforded alkylalkoxyzirconocene or -hafnocene complexes, Cp(2)MR(OR') (M = Zr or Hf, R' = alkyl or aryl) in high yields with high selectivities. High selectivity of monofunctionalization using PPh(2)Cl, SnR(3)Cl or alcohols can be attributed to the different reactivities between monoalkylzirconocenes which are monofunctionalized products and zirconacyclopentanes or dialkylzirconocenes.

Reaction of [Mo(CO)(4)(norbomadiene)] with 4,4',4 ''-tri-tert-butyl-2,2':6',2 ''-terpyridine afforded the complex [Mo(CO)(4)(4,4',4 ''-(t)Bu(3)terpy)] (2), which in solution shows fluxional behavior, observed by H-1 and C-13 NMR studies at between 25 and -70 degrees C. [Mo(CO)(4)(4,4'-(t)Bu(2)bipy)] (1) reacts with I-2 and SnBr4 by oxidative addition to give molybdenum(II) complexes, [Mo(CO)(3)(4,4'-(t)Bu(2)bipy)I-2] (3) and [Mo(CO)(3)(4,4'-(t)Bu(2)bipy)(SnBr3)Br] (4). The related compounds [Mo(CO)(4,4'-(t)Bu(2)bipy)X(2)] (X = Br(5) or Cl(6)) have been prepared by oxidation of 1 with two equivalents of CuX(2). The IR spectra of 3 in different polar solvents suggest that this compound exists in solution in two isomeric forms, which are in equilibrium. The NMR spectra of 3, 5 and 6 are temperature dependent, indicating their dynamic behavior in solution. Delta G double dagger values for the fluxional process of about 47 kJ mol(-1) and about 53 kJ mol(-1) have been obtained for 5 and 6 respectively. Low temperature C-13 NMR studies of 4 have shown that this compound in solution has a different kind of fluxional behavior.

Novel type of carbozirconation reaction of alkynes is reported. Treatment of zirconocene-alkyne complexes, zirconacyclopentenes, or zirconacyclopentadienes with allylic compounds gave allylzirconation products of alkynes. Carbozirconation of alkynes with zirconacyclopentenes or zirconacyclopentadienes involved beta,beta'-C-C bond cleavage reaction of zirconacycles. Reactions of zirconacyclopentenes with homoallyl bromides afforded allylcyclopropane derivatives as carbozirconation products.

The reaction of zirconacyclopentenes with allyl chloride in the presence of a copper salt and a lithium or magnesium salt proceeds at the alkenyl carbon on zirconium with high chemoselectivity; selective C-C bond formation at the alkyl carbon was also achieved by treatment of zirconacyclopentenes with a copper salt and a lithium or magnesium salt, methanol and allyl chloride.

Zirconacyclopentadienes reacted with 2 equiv of allyl chloride in the presence of either a catalytic or a stoichiometric amount of CuCl and LiCl salts (2 equiv) to give stereodefined 1,4,6,9-decatetraenes in 66-96% yields; Reaction of 1,4,6,9-decatetraenes obtained here such as 4,5,6,7-tetraethyldeca-1,4,6,9-tetraene with 1 equiv of Negishi reagent (Cp(2)ZrCl(2) + 2 n-BuLi) in THF at room temperature for 3 h and subsequent carbonylation at 0 degrees C gave eight-membered-five-membered fused-ring ketones such as 3,4,5,6-tetraethylbicyclo[6.3.0]-undeca-3,5-dien-10-one in 76% yield.

An ethylene-bridged zirconocene complex, (Cp(2)ZrMe)2(CH2CH2), was prepared by the reaction of Cp(2)ZrMe(2) with a zirconocene-ethylene complex, [Cp(2)ZrEt(CH2=CH2)]MgBr, and the structure of this complex was determined by a single-crystal X-ray diffraction study. The structure of this complex showed one methyl group on each zirconium and an ethylene ligand simultaneously coordinating to the two zirconocene moieties.

Intramolecular cyclization reactions of YCH2CH=CHCH(2)XCH(2)CH=CH2 (X = CH2, NPr, NPh; Y = PhO, MeO), which have a terminal double bond and an allylic ether moiety, were catalyzed by zirconocene dichloride (10-20 mol %) in the presence of n-BuMgCl. Cyclization products 2-methyl-1-vinylcyclopentane, 4-methyl-1-propyl-3-vinylpyrrolidine, and 4-methyl-1-phenyl-3-vinylpyrrolidine were obtained in 60-80% yields. Stoichiometric cyclization with Cp(2)ZrBu(2) or (C(5)H(3)Me(2))(2)ZrBu(2) at room temperature gave the same products in high yields after hydrolysis. When an excess Of CP(2)ZrBu(2) was used, the stereoisomerization of cis product to trans isomer was observed.

Reaction of allylzirconation products of alkynes with allyl chloride was catalyzed by copper salts to give stereodefined 1,4,7-trienes.

Zirconacyclopentenes, which were readily prepared by the reaction of Cp2ZrEt2 with alkynes or by the reaction of vinylsilane with alkynes in the presence of Cp2ZrBu2 (Negishi reagent), reacted with iodine to give either stereodefined alkenyl iodides or homoallylic iodides selectively after hydrolysis. The chemoselectivity of this reaction was strongly dependent on the substituent R group of the C2 carbon attached to zirconium. When R was a phenyl group, homoallylic iodides were selectively formed. On the other hand, alkyl substituted zirconacyclopentenes reacted with iodine to afford alkenyl iodides selectively. A small amount of diiodides were produced as by-products. Reactions of zirconacyclopentenes with an excess of MeOH and iodine in this order gave only alkenyl iodides with excellent selectivities. The formation of diiodides was not detected. This monohalogenation procedure using an excess of MeOH/I2 was not substituent dependent in the system used here. Treatment of alkylsubstituted zirconacyclopentenes with CBr4 or CCl3Br yielded only homoallylic bromides, after hydrolysis, with >99% chemoselectivity. It is in sharp contrast to the reaction with usual bromination reagents such as Br2 and NBS which led to the selective formation of alkenyl bromides. A sequential treatment of zirconacyclopentenes with CBr4 and I2 in this order, afforded a mixed dihalogenation product selectively. Reaction with Me3SnCl was not substituent dependent. The sp3 carbon attached to Zr selectively reacted with Me3SnCl to give homoallyltin compounds. Insertion reaction of isonitrile in the Zr-carbon bond of zirconacyclopentenes were chemoselective but neither substituent dependent nor reagent dependent in the system used here.

Reactions of zirconocene-alkene complexes Cp2Zr(CH2=CHRXPR3') (R = H, Me, Et, SiR3'' or Ar) with aldehydes or ketones were investigated. Zirconocene-ethylene, -propylene or 1-butene complexes reacted with aldehydes or ketones at terminal carbons of alkenes to give the corresponding alcohols after hydrolysis with a high regioselectivity. A similar type of reaction product was also obtained by a reaction of zirconacyclopentanes with aldehydes. This reaction proceeded via beta-beta' carbon-carbon bond cleavage of zirconacyclopentanes. A reaction of zirconocene-vinylsilane complexes with ketones afforded 3-trimethylsilyl-1-oxa-2-zirconacyclopentanes with an excellent regioselectivity. Carbon-carbon bond formation occurred exclusively at the terminal carbon of vinylsilanes. Their corresponding gamma-silylalcohols were obtained after hydrolysis. The products showed that vinylsilanes reacted with carbonyl compounds at the beta-carbon to silyl group. It is in sharp contrast to the conventional reactions of vinylsilanes of which the alpha-carbon normally attacked electrophiles. The reactions of styrene and its derivatives with pentan-3-one on zirconium gave a mixture of two regioisomers. Substituents of alkenes tend to be in alpha-position to Zr in 1-oxa-2-zirconacyclopentanes. This orientation showed a different aspect of the formation of 1-oxa-2-zirconacyclopentanes from the alkene-alkene coupling reaction on zirconium. The regioselectivity of the reaction with carbonyl compounds decreased in this order; R = alkyl > silyl > aryl.

Zirconium-alkyne complexes or zirconacyclopentenes, which were easily prepared in situ from alkynes, reacted with acrolein diethylacetal to afford vinyl ether derivatives. The C-C bond formation proceeded exclusively at beta-position of the alpha,beta-unsaturated acetal. Zirconium catalyzed C-C bond formation reactions of alpha,beta-unsaturated acetals with EtMgBr also proceeded at beta-position exclusively.

The carbon-carbon bond formation reactions of diynes with EtMgBr can be catalyzed by Cp(2)ZrCl(2). The final products, magnesiated enynes, readily undergo stereoisomerization to give a mixture of (E) and (Z) isomers. The stoichiometric reaction of diynes with ethylene zirconocene gives zirconacyclopentenes with alkynyl substituents in the alpha position with high regioselectivities.