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An in situ generated cationic allylpalladium complex bearing N-heterocy- clic carbene (NHC) ligands, derived from the reaction of ((g 3 -C3H5)Pd(NHC)Cl) with AgX (X ¼ BF4 or SbF6), is an active catalyst for the addition polymerization of norbor- nene and norbornene derivatives (5-norbornene-2-carboxylic acid methyl ester (b )a nd 5-norbornene-2-carboxylic acid n-butyl ester (c)) with an ester group containing a large portion of endo-isomers. The catalytic activities, polymer yields, molecular weights, and molecular weight distributions of polynorbornenes were investigated under various reaction conditions: the catalytic activity was highly dependent on the counteranion, the reaction solvent, and the reaction temperature. For b, as the portion of an endo-iso- mer increased, the activity of 13(SbF � ) was much higher than those of 14 and 15 ,a nd for c (exo/endo ¼ 95:5), the maximum turn over number (TON) was observed with 15(SbF � ). V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3042-3052, 2007

Various iridium complexes consisting of phenylpyrazole (ppz) ligands and isoquinolinecarboxylic acids (iq) as ancillary ligands were designed by energy band-gap calculations via ab initio calculations and synthesized to give rise to various emission wavelengths as expected. Fine color tuning was achieved through varying the position of the methyl substituent on the phenylpyrazole moiety with HOMO electron densities. Additional color tuning was made possible by altering the LUMO through the use of different ancillary ligands such as 1-isoquinolinecarboxylic acid (1iq) and 3-isoquinolinecarboxylic acid (3iq).

Cyclopentadiene compounds, 2-[CR'R(OMe)]-1,3-Me 2 C 5 H 3 (R, R' = 2,2'-biphenyl, 2) and 2-[CR'R(OSiMe 3 )]-1,3-Me 2 C 5 H 3 (R, R' = 2,2'-biphenyl, 3; R = ph, R' = ph, 4; R = 2-naphthyl, R' = H, 5) are readily synthesized from 2-bromo-3-methoxy-1,3-dimethylcyclopentene (1). Reaction of the cyclopentadienes with Ti(NMe 2 ) 4 in toluene results in clean formation of the cyclopentadienyl tris(dimethylamido)titanium complexes, which are transformed to the trichloride complexes, 2-[CR'R(OMe)]-1,3-Me 2 C 5 H 2 }TiCl 3 (R, R' = 2,2'-biphenyl, 6) and {2-[CR'R(OSiMe 3 )]-1,3-Me 2 C 5 H 2 }TiCl 3 (R, R' = 2,2'-biphenyl, 7; R = ph, R' = ph, 8; R = 2-naphthyl, R' = H, 9). Attempts to form C1-bridged Cp/oxido complexes by elimination of MeCl or Me 3 SiCl were not successful. X-ray structures of 6, 7 and an intermediate complex {2-[Ph 2 C(OSiMe 3 )]-1,3-Me 2 C 5 H 2 }TiCl 2 (NMe 2 ) (10) were determined.

C1-bridged and Me2Si-bridged 2,5-dimethylcylcopentadienyl ansa-zirconocene complexes, [Me(H)C(C5H4)(2,5-Me2C5H2)]ZrCl2 (6), [(CH3CH2CH2)(H)C(C5H4)(2,5-Me2C5H2)]ZrCl2 (9), [(Me)(H)C(2,5-Me2C5H2)2]ZrCl2 (13), and [Me2Si(2,5-Me2C5H2)2]ZrCl2 (15), are prepared by using 2-bromo-3-methoxy-2,5-dimethylcyclopentene (7) as a starting material. Solid structures of 6 and 13 were determined by X-ray crystallography. The C1-bridged zirconocene complexes 6, 9, and 13 are highly active for ethylene/norbornene copolymerization with high incorporation of norbornene, while the Me2Si-bridged complex 15 shows relatively low activity. Complex 9 shows the highest activity and the highest incorporation of norbornene among the complexes, but the molecular weight of the obtained polymer is relatively low.

A cyclopentadiene compound having methyl substituents on 1,3-positions, 1,3-Me2-2-CH2(OTHP)-C5H3 (3) is prepared from 2-bromo-3-methyl-2-cyclopenten-1-one ethylene ketal (1) in 48% overall yield. Addition of 2.5 equivalents of indenyllithium to 3 affords a methylene bridged 1,3-dimethylcyclopentadienyl indenyl compound, CH2(1,3-Me2C5H3)(C9H7) (5) in 72% yield. Reaction of dilithium salt of 5 with ZrCl2(NMe2)2 (DME) furnishes an ansa-zirconocene complex [CH2(1,3-Me2C5H2)(C9H6)]Zr(NMe2)2 (6), which is transformed cleanly to the dichloride complex, [CH2(1,3-Me2C5H2)(C9H6)]ZrCl2 (7), by treatment of Me3SiCl. Hydrogenation of 7 over PtO2 gives a tetrahydroindenyl complex [CH2(1,3-Me2C5H2)(C9H10)]ZrCl2 (8). Reaction of the dilithium salt of 5 with Ti(NMe2)2Cl2 does not provide the desired ansa-titanocene complex, but a dinuclear complex [(1,3-Me2C5H2)Ti(NMe2)2Cl]–CH2–[(C9H6)Ti(NMe2)Cl] (9) is obtained. The solid structures of 6 and 9 were determined by X-ray crystallography. The ethylene and ethylene/norbornene (co)polymerizations were studied with 7/MAO and 8/MAO.

Deprotonation of 2-acetylpyridine with KH in THF afford a potassium enolate compound (2) which reacts with Zr(NEt2)2Cl2(THF)2 and Ti(NMe2)2Cl2 to yield [CH2C(C5H4N)O-κ2N,O]2M(NR2)2 (M=Zr, R=Et, 3; M=Ti, R=Me, 4) in 84% and 76% yield, respectively. Deprotonation of imines derived from 2-acetylpyridine, (2,6-Me2C6H3)NC(C5H4N)(CH3) (5) and (2,6-iPr2C6H3)NC(C5H4N)(CH3) (6), affords potassium enamides, K[(2,6-Me2C6H3)N–C(C5H4N)(CH2)] (7) and K[(2,6-iPr2C6H3)N-(C5H4N)(CH2)] (8). Reactions of the potassium salt 7 with Zr(NEt2)2Cl2(THF)2 and Ti(NMe2)2Cl2 afford pyridineenamido complexes, [(2,6-Me2C6H3)NC(C5H4N)(CH2)-κ2N,N]2M(NR2)2 (M=Zr, R=Et, 9; M=Ti, R=Me, 10). Reaction of 8 with Zr(NEt2)2Cl2(THF)2 affords [(2,6-iPr2C6H3)NC(C5H4N)(CH2)]2Zr(NEt2)2 (11) but the reaction of 8 with Ti(NMe2)2Cl2 yields [(2,6-iPrC6H3)NC(C5H4N)(CH2)]TiCl(NMe2)2 (12). Addition of excess AlMe3 to 3 or 4 results in transmetallation of Zr or Ti to Al to afford an aluminum enolate complex, [CH2C(C5H4N)(OAlMe3)-κ2N,O]AlMe2 (13). Addition of AlMe3 to 12 results in the formation of a transmetallated complex, [(2,6-iPr2C6H3)NC(C5H4N)(CH2)]AlMe2 (14). The solid structures of 4, 11, 13 and 14 were determined by X-ray crystallography.

sp3-C1-Bridged Cp/amido titanium and zirconium complexes are synthesized by using novel fulvenes that have substituents in the 1-, 4-, and 6-positions only. Thus, the nucleophilic attack of lithium tert-butylamide on 1,4-dimethyl-6-phenylfulvene, 6-(2-furyl)-1,4-dimethylfulvene and 6-cyclohexyl-1,4-dimethylfulvene, and subsequent aqueous workup, yields tBuN(H)−CHR−C5H3Me2 (R = phenyl, 6; R = 2-furyl, 7; R = cyclohexyl, 8) in 80, 88, and 60% yields, respectively. The reactions of the ligands with M(NMe2)4 (M = Ti or Zr) afford the desired bis(dimethylamido) complexes, which can be transformed by treatment with Me2SiCl2 to the dichloride complexes, (1,3-Me2C5H2−CHR−NtBu−κN)MCl2 (M = Ti, R = phenyl, 10; M = Zr, R = phenyl, 11; M = Ti, R = 2-furyl, 13; M = Zr, R = 2-furyl, 14; M = Zr, R = cyclohexyl, 15). Complex 10 is very sensitive towards water, such that an oxo-bridged dimer, (1,3-Me2C5H2−CHPh−NHtBu)ZrCl2−μO−ZrCl2(1,3-Me2C5H2−CHPh−NHtBu) (12), is easily formed by the abstraction of water from the solvents. The solid structures of (1,3-Me2C5H2−CHPh−NtBu−κN)Zr(NMe2)2, 10, 11, and 12 have been determined by X-ray crystallography. The complexes are active towards the polymerization of ethylene when activated with MAO. The activities are rather low and the molecular weight distributions are broad (Mw/Mn = 10−36). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The new organometallic compounds [{(E)-2-SC4H3CHCHC6H4-X-p}Ru(C6Me6)][CF3SO3]2 (X = MeO (1), Me (2), H (3), Br (4), NO2 (5)), bearing a (thiophene)Ru(C6Me6)2+ fragment in the end group, have been p...

The ferrocenyl bipyridines, 1,1'-bis(2-(4-pyridyl)vinyl)ferrocene (1a) and 1,1'-bis(2-(3-methyl-4- pyridyl)vinyl)ferrocene (1b), were cocrystallized with aromatic acids such as 4-alkoxybenzoic acids (2), terephthalic acid (3a), isophthalic acid (3b), phthalic acid (3c), and trimesic acid (4). Eight complexes were obtained as single crystals, and their crystal structures were successfully determined by X-ray analysis. When 1a was assembled with 2 ,a( 1+ 2) self-assembly occurred, to generate supramolecular arrays in which one molecule of 1a and two molecules of 2 were held together through hydrogen bonding. In the cocrystallization of ferrocenyl bipyridines with benzene dicarboxylic acid (3a, 3b, and 3c), proton transfer occurred depending on the kind of benzene dicarboxylic acid. Thus, the cocrystals of 1a + ‚3b - , 1b + ‚3b - , and 1b + ‚3c - consist of proton-transferred ionic supramolecular species, whereas that of 1b‚3a are composed of (2 + 2) assembled cyclic supramolecular structures. Complexation of 1a with 4 afforded the (2 + 3) self-assembly with an intriguing prismatic cagelike structure.

Cocrystals derived from 1,1′-bis(ethenyl-4-pyridyl)ferrocene (1) and resorcinol/phloroglucinol and a crystal of 1,1′-bis(ethenyl-4-quinolinyl)ferrocene (5) have been studied with the aim of engineering crystalline NLO materials. X-ray structure analyses revealed a NLO active syn-type molecular conformation of 1 and 5 via hydrogen bonding with resorcinol/phloroglucinol and π-π interaction between quinoline rings, respectively. For 5, all molecular dipoles are aligned in the same direction and the SHG efficiency is about 4 times that of urea. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

[ N -(2-Benzoylphenyl)benzamido-κ 2 N,O ](η 1 -benzyl)(trimethylphosphine)Ni(II) ( 3 ) is prepared by the reaction of potassium N -(2-benzoylphenyl)benzamide and Ni(η 3 -CH 2 C 6 H 5 )Cl(PMe 3 ). When 3 is treated with one equivalent of B(C 6 F 5 ) 3 , one obtains a zwitterionic complex, [PhC(O)C 6 H 4 NC(Ph)OB(C 6 F 5 ) 3 -κ 2 N,O ]Ni(η 1 -CH 2 C 6 H 5 )(PMe 3 ) ( 4 ). When two equivalents of B(C 6 F 5 ) 3 is added, PMe 3 is abstracted to give a η 3 -benzyl zwitterionic complex, [PhC(O)C 6 H 4 NC(Ph)OB(C 6 F 5 ) 3 -κ 2 N,O ]Ni(η 3 -CH 2 C 6 H 5 ) ( 5 ). Solid structures of 4 and 5 were determined by X-ray crystallography. When ethylene is added to 5 , low molecular weight polyethylene is obtained.

Deprotonation of the α-diimine compound {2,6-(CHMe2)2-C6H3}NC(CH3)C(CH3)N{2,6-(CHMe2)2-C6H3} with excess KH in THF gives dipotassium N,N‘-(1,2-dimethylene-1,2-ethanediyl)bis(2,6-diisopropylanilide) (1) in 75% yield. Reaction of 1 with bis(2-picolyl)zirconium dichloride generated in situ by the reaction of ZrCl4 and 2 equiv of (2-picolyl)potassium affords [N,N‘-(1,2-dimethylene-1,2-ethanediyl)bis(2,6-diisopropylanilido)-κ2N,N‘]bis(2-picolyl)zirconium(IV) (2) in 35% yield. Similar reaction of 1 with LMCl3 (L = Cp, Cp*; M = Zr, Hf) gives the desired complexes {2,6-(CHMe2)2-C6H3}NC(CH2)C(CH2)N{2,6-(CHMe2)2-C6H3}MLCl (L = Cp*, M = Zr, 4; L = Cp*, M = Hf, 5; L = Cp, M = Zr, 6) in 79%, 94% and 54% yields, respectively. Reaction of the chloride complexes with MeMgBr affords the corresponding methyl complexes {2,6-(CHMe2)2-C6H3}NC(CH2)C(CH2)N{2,6-(CHMe2)2-C6H3}MLMe (L = Cp*, M = Zr, 7; L = Cp*, M = Hf, 8; L = Cp, M = Zr, 9) in 63%, 69% and 90% yields, respectively. The solid-state structure of 7 was determined. Wh...

A series of new donor/acceptor compounds of the form [(HC/C/CH/CH/C6H4/X-p )Co2(CO)4(L 1 )(L 2 )])] (2 ,X /Br, L 1 / L 2 /CO; 3 ,X /NO2 ,L 1 /L 2 /CO; 6 ,X /NO2 ,L 1 /CO, L 2 /PPh3; 7 ,X /NO2 ,L 1 /L 2 /PPh3; 8 ,X /NO2 ,L 1 /AsPh3, L 2 /PPh3), where X is a p-acceptor group and the (alkyne)Co2(CO)4(L 1 )(L 2 ) moiety is a donor, has been synthesized. The different s-donor/p-acceptor abilities of the ligands L 1 and L 2 allow tuning of the electronic and optical properties of complexes 2, 3 and 6/8: the hyperpolarizability values increase in the order 2 B/3 B/6 B/7 B/8. Density functional calculations reveal that the absolute values of b do not agree with experimental results, but the general trends are consistent with experiments. The X-ray crystal structures of 2, 6, and 7 are reported. # 2002 Elsevier Science B.V. All rights reserved.

Reactions of ferrocenyl dipyridines (1a,b) with terephthalic (2) and trimesic acid (4) form [2+2] and [3+2] supramolecular assemblies 3 and 5, respectively. Crystallographic analyses reveal that they are stabilized by cooperative noncovalent interactions involving multiple hydrogen-bonding and π−π interactions.

Treatment of (arene)tricarbonylmanganese cations (arene = phenol, cresol) with nucleophiles affords η5-cyclohexadienyl complexes that can be demetalated to give ortho-substituted phenols. Acylation of the phenolic oxygen in the η5-cyclohexadienyl complexes obtained from phenol, followed by treatment with acid, gives manganese tricarbonyl cations with coordinated monosubstituted arenes. Reaction of η5-cyclohexadienyl complexes derived from ortho- and para-cresol with acid gives meta-substituted toluene manganese tricarbonyl cations, and those derived from meta-cresol give ortho- and/or para-substituted toluene manganese complexes depending upon the nucleophiles.

The structures of complex anions, [Al(edta)]- and [Ga(edta)]- (H4edta = ethylenediaminetetraacetic acid), were investigated both in the solid state (X-ray crystallography) and in solution (1H and 13C NMR). Two complexes, (NH4)[Al(edta)]·2H2O (1) and (NH4)[Ga(edta)]·2H2O (2), are isostructural in the solid state. In both metal complexes, the central metal atoms are coordinated by six donor atoms (N2O4) in distorted octahedral coordination geometries in which two nitrogen atoms and two oxygen atoms of two acetate groups occupy the equatorial positions, and the axial positions are occupied by two oxygen atoms of two acetate groups. The 1H and 13C NMR spectra of 1 and 2 showed that acetate groups undergo rapid interchanges between the axial and equatorial positions in solution, its rate in D2O being much faster than that in dimethyl sulfoxide(dmso)-d6 for each complex, and its rate for 1 being slower than that for 2. Based on the NMR spectra, the structures of complex anions [Al(edta)]- and [Ga(edta)]- in sol...

Employing pyrimidine-containing ligands such as 1-(4-pyridyl)-2-(4-pyrimydyl)ethene (L1) and 1-(4-pyridyl)-2-(3-methyl-4-pyridyl)ethene (L3) in assembly with Co(SCN)2 affords robust porous coordination polymers with uncoordinated nitrogen atoms on the channel walls.

Assemblies of 1-methyl-1',2-bis(4-pyridyl)ethene (mpe) and Co(NCS)(2) afford three isomeric framework networks and different topological features depending on the assembly conditions. Isomerism control and solid-to-solid transformation phenomena are observed among them.

Self-assembly between simple unsymmetrical ligands, such as 1-(3-pyridyl)-2-(4-pyridyl)ethene (L(1)) and 1-methyl-1'-(3-pyridyl)-2-(4-pyrimidyl)ethene (L(2)), and Co(NCS)(2) affords the unprecedented two-dimensional grid coordination polymers [Co(L(1))(2)(NCS)(2)](infinity) (1) and [Co(L(2))(2)(NCS)(2)](infinity) (2), respectively, with novel topological features which cannot be achieved using symmetrically bridging ligands.

Total synthesis of SCH 351448 was accomplished employing the ring-closing olefin metathesis reaction for the preparation of the 28-membered macrodiolide.

The assembly of Co(NCS)(2) with 1-methyl-1'-(3-pyridyl)-2-(4-pyridyl)ethene (L(1)) exhibits a novel supramolecular isomerism of [Co(L(1))(2)(NCS)(2)](infinity) caused by different placement orientation of L(1) around metal centers. The reaction in MeOH/H(2)O and EtOH/H(2)O resulted in a double chain structure of 1, and that in EtOH/CH(3)NO(2) led to an open framework structure of 2. The reaction in MeOH/CH(3)NO(2) solvent system concomitantly afforded 1 and 2. The assemblies of 1-(3-pyridyl)-2-(4-pyrimidyl)ethene (L(2)) with Co(NCS)(2) created the water-coordinated complexes of Co(L(2))(2)(H(2)O)(2)(NCS)(2) (3 and 4), an MeOH coordinated complex of Co(L(2))(2)(H(2)O)(2)(NCS)(2) (5), and an open framework coordination polymer of [Co(L(1))(2)(NCS)(2)](infinity) (6) depending on the reaction solvent system. From these observations, it is suggested that in the formation of 1, the solvent-coordinated intermediate species would be generated first and its trans coordination configuration should define the placement orientation of L(1) in the resulting polymer of 1. On the other hand, it is presumed that the solvent-coordinated intermediate would not be produced during the formation of 2 due to the weaker coordination ability of EtOH and CH(3)NO(2) molecules. The open framework coordination polymers of 2 and 6 are converted in the solid state into the isomeric coordination polymer of 1 and hydrogen bonded network structure of 3, respectively.

The highly stereoselective synthesis of β-amino acids via the chiral 4-phenyloxazolidinone-controlled linear N-acyliminium ion reaction has been achieved by employing chiral N,O-acetal TMS ethers. In addition, the mechanism of the excellent stereochemical outcome has been elucidated. The oxazolidinone auxiliary plays a dual role in stereocontrol: the E/Z geometry control of the N-acyliminium ion induced by an initial stereoselective amide reduction, leading to the chiral N,O-acetal TMS ether, and face control of the nucleophile attack in the N-acyliminium ion reaction.

Self-assemblies of rigid angular ligands with 120 degrees molecular angle and metal centers have been investigated with the aim of achieving the rational construction and modification of coordination polymer structures. The reactions of Co(NCS)(2) with 1,3-bis(trans-4-styrylpyridyl)benzene (L(1)()), 2,6-bis(trans-4-styrylpyridyl)pyridine (L(2)()), 1,3-bis(trans-4-styrylpyrimidyl)benzene (L(3)()), and 1,3-bis(trans-4-styrylquinoly)benzene (L(4)()) afford complexes [Co(L(1)())(2)(NCS)(2)]( infinity ) (1), [Co(L(2)())(2)(NCS)(2)]( infinity ) (2), Co(L(3)())(2)(NCS)(2)(CH(3)OH)(2) (3), and [Co(L(4)())(NCS)(2)]( infinity ) (4), respectively. The resulting complexes exhibit open framework, stairlike hydrogen-bonded chain and single-stranded helical coil structures, which are controlled by the variation of the geometry around the coordination site in ligands. Moreover, the coordination of L(1)() and L(2)() to Mn(hfac)(2) (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) yields single-stranded helical coordination polymers of [Mn(L(1)())(hfac)(2)]( infinity ) (5) and [Mn(L(2)())(hfac)(2)]( infinity ) (6), respectively.

[reaction: see text] The highly stereoselective synthesis of beta-amino acids via the chiral 4-phenyloxazolidinone-controlled linear N-acyliminium ion reaction has been achieved by employing chiral N,O-acetal TMS ethers. In addition, the mechanism of the excellent stereochemical outcome has been elucidated. The oxazolidinone auxiliary plays a dual role in stereocontrol: the E/Z geometry control of the N-acyliminium ion induced by an initial stereoselective amide reduction, leading to the chiral N,O-acetal TMS ether, and face control of the nucleophile attack in the N-acyliminium ion reaction.

Reaction of Co(NCS)2 with 1-methyl-1'-(4-pyridyl)-2-(4-pyrimidyl)ethylene (mppe) in different solvents yields two kinds of novel coordination polymer structures of [Co(mppe)2(NCS)2]n: one of them shows an unprecedented interpenetrating structure with both 2D and 3D topological isomers.

Bowl-shaped superstructures have been constructed by intra-clipping of resorcin[4]arene derivatives with two equivalents of (en)Pd(NO3)2 in water. The binding phenomena of the aromatic carboxylates were proven to be both enthalpically and entropically favoured.

The self-assembly of metallosupramolecules from reactions of flexible 2-pyridyl ligands and silver salts is described. When 1,3-bis(2-pyridyl)propane (L1), tris[(2-pyridyl)methyl]methane (L2), and 1,3-bis(2-pyridyl)-2-tolylpropane (L3) are used in combination with silver ions, novel discrete metallocyclic complexes are formed in crystals. Moreover, the self-assembly of 1,3-bis(2-pyridyl)-2-phenylpropane (L4) with silver nitrate yields a coordination polymer. The examination of its solution shows that this coordination polymer is formed via the solution-based discrete metallocyclic species.

Condensation reaction of 1,1'-ferrocenedicarboxaldehyde with (1R,2R)-1,2-diaminocyclohexane affords a novel bowl-shaped macrocycle with a chiral concave cavity which exhibits a remarkable ability as a host material for the enantioselective enclathration of 1,1'-bi-2-naphthol.

Bowl-shaped superstructures have been constructed by intra-clipping of resorcin[4]arene derivatives with two equivalents of (en)Pd(NO3)2 in water. The binding phenomena of the aromatic carboxylates were proven to be both enthalpically and entropically favoured.

Addition of primary amines to N-[2-(diphenylphosphanyl)benzoyloxy]succinimide affords 2-diphenylphosphanylbenzamides, Ph2PC6H4C(O)NHR (R = C(CH3)3, 3; R = H, 4; R = CH2CH2CH3, 5; R = CH(CH3)2, 6). Addition of NiCl(eta3-CH2C6H5)(PMe3) to the deprotonated potassium salts of the amides and subsequent treatment of two equivalents of B(C6F5)3 to the resulting products furnishes eta3-benzyl zwitterionic nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta3-CH2C6H5) (R = C6H5, 9; R = C(CH3)3, 10; R = H, 11; R = CH2CH2CH3, 12; R = CH(CH3)2, 13). Solid structures of 9, 11, 13 and the intermediate eta1-benzyl nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta1-CH2C6H5)(PMe3) (R = C6H5, 7; R = C(CH3)3, 8) were determined by X-ray crystallography. When ethylene is added to the eta3-benzyl zwitterionic nickel(II) complexes, butene is obtained by the complexes 9-12 but complex 13 provides very high molecular-weight branched polyethylene (Mw, approximately 1300000) with excellent activity (up to 5200 kg mol-1 h-1 at 100 psi gauge).