Showing papers on "Norbornene published in 2012"
TL;DR: A palladium-catalyzed direct 2-alkylation reaction of free N-H indoles was developed based on a norbornene-mediated regioselective cascade C-H activation, and two structurally different Aspidosperma alkaloids were synthesized in concise routes.
Abstract: A palladium-catalyzed direct 2-alkylation reaction of free N-H indoles was developed based on a norbornene-mediated regioselective cascade C–H activation. The detailed reaction mechanism was investigated by NMR spectroscopic analyses, characterization of the key intermediate, deuterium labeling experiments, and kinetic studies. The results indicate that a catalytic cycle operates, in which an N-norbornene type palladacycle is formed as the key intermediate. Oxidative addition of alkyl bromide to the Pd(II) center in this intermediate is the rate-determining step of the reaction. The synthetic utility of this indole 2-alkylation method was demonstrated by its application in natural product total synthesis. A new and general strategy to synthesize Aspidosperma alkaloids was established employing the indole 2-alkylation reaction as the key step, and two structurally different Aspidosperma alkaloids, aspidospermidine and goniomitine, were synthesized in concise routes.
289 citations
TL;DR: The relationship between alkene structure and reactivity in thiol-ene reactions is derived from the results of kinetic modeling and can be directly related to the relative energy of stationary points obtained from electronic structure calculations.
Abstract: The influence of alkene functionality on the energetics and kinetics of radical initiated thiol–ene click chemistry has been studied computationally at the CBS-QB3 level. Relative energetics (ΔH°, ΔH⧧, ΔG°, ΔG⧧) have been determined for all stationary points along the step-growth mechanism of thiol–ene reactions between methyl mercaptan and a series of 12 alkenes: propene, methyl vinyl ether, methyl allyl ether, norbornene, acrylonitrile, methyl acrylate, butadiene, methyl(vinyl)silanediamine, methyl crotonate, dimethyl fumarate, styrene, and maleimide. Electronic structure calculations reveal the underlying factors that control activation barriers for propagation and chain-transfer processes of the step-growth mechanism. Results are further extended to predict rate constants for forward and reverse propagation and chain-transfer steps (kP, k–P, kCT, k–CT) and used to model overall reaction kinetics. A relationship between alkene structure and reactivity in thiol–ene reactions is derived from the results ...
216 citations
TL;DR: This project shows that requirments for the incorporation of special unnatural amino acid into proteins to enable site-specific bioorthogonal functionalization can be met with a specially encoded norbornene amino acid which reacts selectively with nitrile imines.
Abstract: Methods for the site-specific chemical modification of proteins are currently of immense importance for the synthesis of protein–hybrid compounds for pharmaceutical and diagnostic purposes. Most of the methods rely on the reaction of free protein thiols with maleimides or the reaction of lysine side chains with activated esters. These methods provide only limited specificity, which is prompting researchers to develop alternative strategies that involve the incorporation of special unnatural amino acid into proteins to enable site-specific bioorthogonal functionalization. Among the developed methods, the Cu-catalyzed reaction of a protein containing an alkyne amino acid with azides stands out as the most thoroughly investigated technology. 6] However, the need for Cu salts, which may harm the protein structure, limits the technology. This fuels current interest to develop copperfree coupling reactions that are compatible with fragile protein structures. Here we show that these requirments can be met with a specially encoded norbornene amino acid which reacts selectively with nitrile imines. In order to insert a norbornene amino acid into a protein we used the amber suppression technique based on the pyrrolysyl tRNA/pyrrolysyl-tRNA synthetase (tRNA/ PylRS) pair from Methanosarcina mazei. The main task of the project was to evolve the pyrrolysine synthetase so that it accepts the synthetic norbornene amino acid 1 (Scheme 1 a) for loading onto the pyrrolysyl-tRNA. For the study we synthesized the norbornene-containing Pyl analogue 1 in seven steps from readily available starting materials (see the Supporting Information). To test to what extent 1 is accepted by wild-type (wt) PylRS, we used E. coli cells encoding the full tRNA/PylRS pair and a modified yellow fluorescent protein (YFP) containing one in-frame TAG stop codon. In this system the full-length and hence fluorescent YFP can only be produced when the corresponding Pyl analogue is accepted by the PylRS and successfully loaded onto the tRNA for subsequent incorporation into the protein at the amber stop codon site. The so-prepared E. coli cells were grown in a medium containing 5 mm 1. In addition to the wild-type PylRS we also tested a PylRS mutant (Y384F) previously used by Yanagisawa and co-workers. These initial experiments provided a just faint fluorescence when the mutant PylRS(Y384F) was used. No flurescence and hence no full-length YFP was generated in the presence of wild-type PylRS. In order to increase the PylRS activity we evolved the protein using iterative saturation mutagenesis (ISM) developed by Reetz and co-workers. Based on the co-crystal structure of PylRS in complex with adenylated pyrrolysine (PDB 2Q7H) we selected five residues in the substrate-binding pocket of wt-PylRS for the experiments. After transformation of the plasmid-based PylRS library into E. coli, single colonies were grown in liquid cultures supplemented with 1. The incorporation was monitored by means of the YFP fluorescence intensity of the cells. The most efficient PylRS variants were then sequenced and used in the next round of the saturation mutagenesis. In Scheme 1. a) Structure of norbornene Pyl analogue 1 and b) schematic representation of the click reactions. Top: A nitrile imine is generated by base-promoted HCl elimination from the hydrazonoyl chloride and then used in a cycloaddition reaction with the norbornene. Middle: Alternatively the nitrile imine is generated from a tetrazole in a photochemical reaction. Bottom: The norbornene modification can also react with tetrazines in a reversed-electron-demand Diels–Alder reaction. (Protein representations generated from PDB 3IN5.)
147 citations
TL;DR: Cis-selective ring-opening metathesis polymerization of several monocyclic alkenes as well as norbornene and oxanorbornene-type monomers using a C-H activated, ruthenium-based metatheses catalyst is reported.
Abstract: Cis-selective ring-opening metathesis polymerization of several monocyclic alkenes as well as norbornene and oxanorbornene-type monomers using a C–H activated, ruthenium-based metathesis catalyst is reported. The cis content of the isolated polymers depended heavily on the monomer structure and temperature. A cis content as high as 96% could be obtained by lowering the temperature of the polymerization.
145 citations
TL;DR: The isolation of reaction intermediate complexes revealed that the η(3)-butadienyl coordination is the key for the selective formation of cyclobutene.
Abstract: A nickel-catalyzed intermolecular [2 + 2] cycloaddition of conjugated enynes with alkenes has been developed. A variety of electron-deficient alkenes as well as electronically neutral norbornene an...
105 citations
TL;DR: The synthesis and characterization of two neutrally charged bimetallic Ni(II) ethylene polymerization catalysts, and their monometallic analogues, exhibit significantly enhanced thermal stability versus the less sterically encumbered dinickel catalyst.
Abstract: The synthesis and characterization of two neutrally charged bimetallic NiII ethylene polymerization catalysts, {2,7-di-[2,6-(3,5-di-methylphenylimino)methyl]1,8-naphthalenediolato}-bis-NiII(methyl)(trimethylphosphine) [(CH3)FI2-Ni2] and {2,7-di-[2,6-(3,5-di-trifluoromethyl-phenylimino)methyl]-1,8-naphthalenediolato}-bis-NiII(methyl)(trimethyl-phosphine) [(CF3)FI2-Ni2)], are reported. The diffraction-derived molecular structure of (CF3)FI2-Ni2 reveals a Ni⋅⋅⋅Ni distance of 5.8024(5) A. In the presence of ethylene and Ni(COD)2 or B(C6F5)3 co-catalysts, these complexes along with their monometallic analogues [2-tert-butyl-6-((2,6-(3,5-dimethylphenyl)phenylimino)methyl)-phenolate]-NiII-methyl(trimethylphosphine) [(CH3)FI-Ni] and [2-tert-butyl-6-((2,6-(3,5-ditrifluoromethyl-phenyl)phenylimino)methyl)phenolato]-NiII-methyl-(trimethylphosphine) [(CF3)FI-Ni], produce polyethylenes ranging from highly branched Mw=1400 oligomers (91 methyl branches per 1000 C) to low branch density Mw=92 000 polyethylenes (7 methyl branches per 1000 C). In the bimetallic catalysts, Ni⋅⋅⋅Ni cooperative effects are evidenced by increased product polyethylene branching in ethylene homopolymerizations (∼3× for (CF3)FI2-Ni2 vs. monometallic (CF3)FI-Ni), as well as by enhanced norbornene co-monomer incorporation selectivity, with bimetallic (CH3)FI2-Ni2 and (CF3)FI2-Ni2 enchaining approximately three- and six-times more norbornene, respectively, than monometallic (CH3)FI-Ni and (CF3)FI-Ni. Additionally, (CH3)FI2-Ni2 and (CF3)FI2-Ni2 exhibit significantly enhanced thermal stability versus the less sterically encumbered dinickel catalyst {2,7-di-[(2,6-diisopropylphenyl)imino]-1,8-naphthalenediolato}-bis-NiII(methyl)(trimethylphosphine). The pathway for bimetallic catalyst thermal deactivation is shown to involve an unexpected polymerization-active intermediate, {2,7-di-[2,6-(3,5-di-trifluoromethyl-phenylimino)methyl]-1-hydroxy,8-naphthalenediolato-NiII(methyl)-(trimethylphosphine).
98 citations
TL;DR: In this article, the same catalyst selectively affords homodimerization products from the starting allene, a process that may be conveniently fine tuned by addition of norbornene.
Abstract: Addition of catalytic amounts of a phosphite-based gold(I) catalyst efficiently triggers the intermolecular [2+2] cycloaddition of allenes and alkenes substituted by electron-donor groups. The reaction is fast and furnishes cyclobutane derivatives in a stereoselective manner using low catalyst loadings. Besides, the same catalyst selectively affords homodimerization products from the starting allene, a process that may be conveniently fine tuned by addition of norbornene.
88 citations
TL;DR: o-Biaryl carbaldeydes and ketones are obtained through the one-pot reaction of o-aryl iodides with o-bromobenzyl alcohols under the catalytic action of Pd and norbornene, in the presence of a base.
81 citations
TL;DR: In this article, a multishape memory copolymers were prepared through copolymerization of two norbornene derivatives: one based on cholic acid and the other based on triethylene glycol monomethyl ether.
Abstract: Multishape memory copolymers were prepared through copolymerization of two norbornene derivatives: one based on cholic acid and the other on triethylene glycol monomethyl ether. The glass transitio...
75 citations
TL;DR: In this paper, a ring-opening polymerization was used to construct a multireactive polymeric scaffold for access to multifunctionalized materials in an undemanding manner.
Abstract: Well-defined norbornene-functional poly(carbonate)s were prepared by ring-opening polymerization and utilized as multireactive polymeric scaffolds in a range of postpolymerization modifications. The norbornene-functional handles were shown to undergo facile reaction with azides via a 1,3-dipolar cycloaddition, tetrazines in the inverse electron demand Diels–Alder reaction and thiols via radical thiol-ene coupling. Furthermore, the above-mentioned chemistries were demonstrated in a sequential one-pot, three-step modification reaction illustrating the potential of these polymers as scaffolds to access multifunctionalized materials in an undemanding manner.
61 citations
TL;DR: In this article, a cyclic olefin copolymer (COC) with high glass transition temperature, good mechanical performance, high transparency, and excellent film forming ability has been achieved in this work by Copolymerization of ethylene and exo-1,4,4a,9,9a,10hexahydro-9,10(1′,2′)-benzeno-l,4-methanoanthracene (HBMN).
Abstract: Novel cyclic olefin copolymer (COC) with high glass transition temperature, good mechanical performance, high transparency, and excellent film forming ability has been achieved in this work by effective copolymerization of ethylene and exo-1,4,4a,9,9a,10-hexahydro-9,10(1′,2′)-benzeno-l,4-methanoanthracene (HBMN). This bulky cyclic olefin comonomer can be simply prepared in good yield via Diels–Alder reaction. By utilizing constrained geometry catalyst (CGC) activated with Al(iBu)3/[Ph3C][B(C6F5)4], ethylene/HBMN copolymer can be obtained with excellent production, high molecular weight, and a wide range of HBMN incorporation. 13C NMR (DEPT) spectra reveal alternating ethylene–HBMN sequence can be detected at high HBMN incorporation. The glass transition temperature (Tg) of resulted copolymer enhances with increasing HBMN incorporation. A high Tg up to 207.0 °C is attainable at low comonomer incorporation of 30.4 mol %, which is 61 °C higher than that of commercial norbornene (NB)-derived COC (54 mol %). T...
TL;DR: A series of novel bis(imino)pyridine nickel(II) dichloride complexes, with the bisimino pyridine ligands containing electron-withdrawing groups (F, Cl, Br, CF3), have been prepared and characterized by elemental analysis and NMR spectroscopy as discussed by the authors.
TL;DR: In this paper, the melt-state phase behavior of an imidazolium-containing alkyl-ionic block copolymer (BCP) was investigated using a combination of small-angle X-ray scattering (SAXS) and sequential ring-opening metathesis polymerization (ROMP).
Abstract: The development of nanostructured polymeric systems containing directionally continuous poly(ionic liquid) (poly(IL)) domains has considerable implications toward a range of transport-dependent, energy-based technology applications. The controlled, synthetic integration of poly(IL)s into block copolymer (BCP) architectures provides a promising means to this end, based on their inherent ability to self-assemble into a range of defined, periodic morphologies. In this work, we report the melt-state phase behavior of an imidazolium-containing alkyl–ionic BCP system, derived from the sequential ring-opening metathesis polymerization (ROMP) of imidazolium- and alkyl-substituted norbornene monomer derivatives. A series of 16 BCP samples were synthesized, varying both the relative volume fraction of the poly(norbornene dodecyl ester) block (fDOD = 0.42–0.96) and the overall molecular weights of the block copolymers (Mn values from 5000–20 100 g mol–1). Through a combination of small-angle X-ray scattering (SAXS) ...
TL;DR: A linear cationdecorated polymeric support with tuneable surface properties and microstructure has been prepared by ring-opening metathesis polymerisation (ROMP) of a pyrrolidinium-functionalised norbornene-based monomer with cyclooctene.
TL;DR: An interesting magenta emission from NDT along with Eu(III) is utilized as a new fluorometric chemodosimeter that selectively detects G-type agent surrogates and the selectivity for reactive surrogates over a variety of other close chemical analogs is demonstrated.
TL;DR: In this article, a β-diiminate zinc catalyst with a norbornene carboxylate initiator was used for the synthesis of multisegmented polycarbonate graft copolymers.
Abstract: We report a method for the synthesis of multisegmented polycarbonate graft copolymers. Using a β-diiminate zinc catalyst with a norbornene carboxylate initiator, we achieved living block copolymerizations of functionalized cyclohexene oxides and CO2, yielding norbornenyl-terminated macromonomers with variable block sequences. Subsequent ring-opening metathesis polymerization of the norbornenyl-terminated macromonomers produced segmented graft copolymers. This method provides a facile route to core–shell structures with readily controllable molecular parameters.
TL;DR: A facile synthesis of oligo(thiophene)-modified (coated) "soluble" star (ball)-shaped polymers has been achieved via sequential living ring-opening metathesis polymerization (ROMP) of norbornene and a cross-linking reagent.
Abstract: A facile synthesis of oligo(thiophene)-modified (coated) “soluble” star (ball)-shaped polymers has been achieved via sequential living ring-opening metathesis polymerization (ROMP) of norbornene and a cross-linking reagent using Mo(CHCMe2Ph)(N-2,6-iPr2C6H3)(OtBu)2 as the initiator and oligo(thiophene) carboxaldehydes for termination. The resultant star-shaped ROMP polymers containing ter- and tetrathiophene moieties exhibit unique emission properties due to an integration of the ROMP polymers (arranged functionalities): the blue emission was tuned to the white emission upon addition of 2-[2-[(E)-4-(dimethylamino)styryl]-6-methyl-4H-pyran-4-ylidene]malononitrile.
TL;DR: In this article, two copolynorbornenes bearing pendant sultone groups were successfully synthesized via copolymerization of functionalized norbornenes with sultones (designated as SulNBOH and SulNBOMe) with 2-butoxymethylene norbornene.
Abstract: Novel copolynorbornenes bearing pendant sultone groups (designated as P(BN/SulNBOH) and P(BN/SulNBOMe)) have been successfully synthesized via copolymerization of functionalized norbornenes bearing sultones (designated as SulNBOH and SulNBOMe) with 2-butoxymethylene norbornene (BN). The catalyst system showed high catalyst activity (104 gpolymer/molNi·h) and the obtained copolymers have high molecular weight and a narrow molecular weight distribution. Furthermore, the achieved copolymers P(BN/SulNBOH) and P(BN/SulNBOMe) were converted into sulfonated copolymers sP(BN/NBOH) and sP(BN/NBOMe). Both sP(BN/NBOH) and sP(BN/NBOMe) membranes displayed low water uptake, high thermal properties, good mechanical properties, and better proton exchange membranes properties. The proton conductivities measured in the hydrated state at 80 °C ranged from 10−5 to 7.19 × 10−3 S·cm−1.
TL;DR: In this article, the second generation alkene metathesis catalyst and the fluorous analog (H2IMes)((Rf8(CH2)2)3P)(Cl)2Ru(═CHPh) (1,3dimesityl-4,5-dihydroimidazol-2-ylidene/(CF2)7CF3) catalyze ring-opening metatonhesis polymerizations of norbornene at essentially identical rates (CDCl3, RT).
Abstract: Grubbs’ second-generation alkene metathesis catalyst and the fluorous analog (H2IMes)((Rf8(CH2)2)3P)(Cl)2Ru(═CHPh) (1; H2IMes/Rf8 = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene/(CF2)7CF3) catalyze ring-opening metathesis polymerizations of norbornene at essentially identical rates (CDCl3, RT). However, dramatic accelerations can be observed with 1 in the presence of the fluorous solvent perfluoro(methylcyclohexane) (PFMC). The fluorous phosphine (Rf8(CH2)2)3P must first dissociate from 1 to generate the 14-valence-electron intermediate that begins the catalytic cycle and should be scavenged by the PFMC phase (PFMC/toluene partition coefficient >99.7:<0.3). This would allow alkenes to more effectively compete for active catalyst. However, faster rates are seen only when 1 (partition coefficient 39.6:60.4) is added as a PFMC solution or a PFMC/CDCl3 biphase mixture, as opposed to CDCl3 solution, and possible additional contributing factors are analyzed. Analogous effects are observed with a 7-oxanorbornene-b...
TL;DR: In this article, a ring-opening metathesis polymerization of norbornene was performed in the presence of vanadium(V)-alkylidene and ordinary Mo(CHCMe2Ph)(N-2,6-iPr2-C6H3)(OtBu)2.
TL;DR: In this article, the surface-initiated ring-opening metathesis polymerization (SI-ROMP) was used to graft cellulose fibres using a Grubbs' type catalyst.
TL;DR: The nickel metal centers adopt distorted square planar geometries with the bromine atoms acting as one coordinate ligands and show moderate activities in butadiene polymerization when activated with alkylaluminium, affording the cis-1,4 enriched polymer.
Abstract: Bis(imino)aryl NCN pincer Ni(II) complexes 2,6-(ArNCH)2C6H3NiBr (1: Ar = 2,6-Me2C6H3; 2: Ar = 2,6-Et2C6H3; 3: Ar = 2,6-iPr2C6H3) were prepared via the oxidative-addition of Ni(0)(Ph3P)4 with bis(N-aryl)-2-bromoisophthalaldimine. These nickel complexes were characterized by NMR and elemental analyses. Their solid molecular structures were established by X-ray diffraction analyses. The nickel metal centers adopt distorted square planar geometries with the bromine atoms acting as one coordinate ligands. The NCN pincer Fe(II) complexes 2,6-(ArNCH)2C6H3Fe(μ-Cl)2Li(THF)2 (4: Ar = 2,6-Me2C6H3; 5: Ar = 2,6-Et2C6H3; 6: Ar = 2,6-iPr2C6H3) were synthesized by lithium salt metathesis reactions of the ligand lithium salts with FeCl2. X-ray structure analyses of 4 and 5 revealed that the Fe(II) complexes are hetero-dinuclear with the iron atoms in trigonal bipyramidal environments. When activated with MAO, the nickel complexes are active for norbornene vinyl polymerization but are inert for butadiene polymerization. The Fe(II) complexes show moderate activities in butadiene polymerization when activated with alkylaluminium, affording the cis-1,4 enriched polymer.
TL;DR: In this article, the ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with 3a-d was studied and the molecular structure of complex 3b was determined by single-crystal X-ray diffraction analysis.
TL;DR: In this article, the vinyl-addition homo-and copolymerization of a norbornene monomer bearing an electron-deficient triarylborane side group (M1 ) using Pd(II) catalyst in the presence of the 1-octene chain transfer agent efficiently produced a novel class of soluble polynorbornenes functionalized with triaryl-borane groups.
TL;DR: The series of anilido-imine N-NP and N-NS tridentate nickel and palladium complexes (ArNHC6H4CH═NPh-2-XPh)MCl as discussed by the authors ] is a series of triidentate Nn and Nn tridentates.
TL;DR: The unusual fluorescence of NDP1 is attributed to the difference between the positions of HOMO and LUMO wave functions that lead to the prevention of non-radiative relaxation pathways and utilized as a new fluorometric sensor that selectively detects Fe(III) ions.
Abstract: This communication describes the synthesis and characterization of norbornene derived phosphonates (NDP1 to NDP3). The unusual fluorescence of NDP1 is attributed to the difference between the positions of HOMO and LUMO wave functions that lead to the prevention of non-radiative relaxation pathways. Due to the significant non-radiative relaxation pathway, the control molecule NDP2 shows weak fluorescence whereas NDP3 shows no fluorescence at all. Similar experiments are carried out on NDPH1, the homopolymer of NDP1. Our hypothesis is further strengthened as there is no emission from NDPH1. The unusual fluorescence is utilized as a new fluorometric sensor that selectively detects FeIII ions.
TL;DR: In this article, the first synthesis of comb-polymers from end-functi cation was reported, where the end-functionalized polymers were converted to hydroxyl-and subsequently norbornene-terminated macromonomers.
Abstract: Using nonliving bis(phenoxyimine)titanium catalysts activated by methylaluminoxane (MAO) in the presence of propylene, allyl-terminated syndiotactic polypropylene macromonomers with varying tacticity ([rrrr] = 0.80 and 0.94) and molecular weight (Mn = 3600 and 5600 g/mol) were produced. The end-functionalized polymers were converted to hydroxyl- and subsequently norbornene-terminated macromonomers. Two series of syndiotactic polypropylene comb-polymers were synthesized through metathesis polymerization of the norbornene-functionalized polypropylene. The molecular weight (Mn = 46 000–172 000 g/mol) and polydispersity (Mw/Mn = 1.21–1.89) of the comb polymers was determined by gel permeation chromatography (GPC). Using differential scanning calorimetry (DSC), melting temperature (Tm) and crystallization temperature (Tc) were determined and both were observed to decrease with increasing conversion to poly(macromonomer). To the best of our knowledge, this is the first synthesis of comb-polymers from end-functi...
TL;DR: In this article, the authors synthesized poly(endo-NDI)s using available Grubbs catalysts, and subsequently hydrogenated their backbone double bonds to obtain high molecular weight samples with Mn ≥ 150,000.
TL;DR: In this article, norbornenes fused with N-aryl-endo-pyrrolidine 9a undergoes ROMP to give polynorbornene with cis, isotactic selectivity.
Abstract: Upon treatment with a molybdenum-carbene with bidentate substituted biaryl-o,o′-diphenoxide ligand 12, norbornene fused with N-aryl-endo-pyrrolidine 9a undergoes ROMP to give exclusively polynorbornene with cis, isotactic-selectivity. Bis(norbornenes) connected with ferrocene 18 or benzene 20 linkers yield the corresponding double-stranded ladderphanes 19 and 21, respectively with isotactic stereochemistry having all double bonds in Z-configuration. Like the corresponding ladderphanes with E-double bonds, ladderphane 19 also assembles on HOPG to give a highly ordered two-dimensional array as revealed by STM images.
TL;DR: In this article, the reactions of the bimetallic compound Na[W2(µ-Cl)3Cl4(THF)2]·(thf)3 (1, (W 3 W)6+, a'2e'4) with norbornene (NBE) and some of its derivatives (5-X-2-NBE; X = COOH (N BE-COOH), NBE-COCOH), OH (nBE-OH), CN (nbe-CN), COOMe
Abstract: In this study, the reactions of the bimetallic compound Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3 (1, (W 3 W)6+, a'2e'4) with norbornene (NBE) and some of its derivatives (5-X-2-NBE; X = COOH (NBE–COOH), OH (NBE–OH), CN (NBE–CN), COOMe (NBE–COOMe), CH=CH2 (VNBE); norbornadiene (NBD)) are described. Complex 1 contains a tungsten–tungsten triple bond, bearing three halide bridges and two labile THF ligands, in a cisoidal relationship along the metal–metal axis. The complex was found to be a highly efficient room temperature homogeneous and heterogeneous unicomponent initiator for the catalytic ring opening metathesis polymerization (ROMP) of most substrates. NBE provides polynorbornene (PNBE) of high molecular weight (Mw) in high yields, soluble in organic solvents. The reaction proceeds with high cis-stereoselectivity (80%–86% cis), independently of the reaction conditions. Strongly coordinating pendant groups (–COOH, –OH, –CN) deactivate 1, whereas substrates bearing softer ones (–COOMe, –CH=CH2) are quantitatively polymerized. NBD gives quantitatively insoluble PNBD. The polymers have been characterized by 1H, 13C NMR and Size Exclusion Chromatography (SEC). Monitoring the reactions in situ by 1H NMR (1/NBD or NBE) provides direct evidence of the metathetical nature of the polymerization with the observation of the active tungsten alkylidene propagating polymeric chains. Mechanistic aspects of the reactions are discussed.