Bipyridyl Adducts Research Articles

The march of progress: structures of the adducts of potassium dicyanidoaurate(I) with 2,2'-bipyridyl (redetermination) and 1,10-phenanthroline.

The structure of the 2,2'-bipyridyl adduct poly[(μ2-2,2'-bipyridyl-κ3N,N':N)di-μ3-cyanido-κ6C:N:N-gold(I)potassium(I)], [AuK(CN)2(C10H8N2)]n, (1) (space group P21), has been redetermined [previous determination: Jones et al. (1980). Acta Cryst. B36, 160-162]. The bipyridyl ligands coordinate only the potassium ion, which has a coordination sphere consisting of seven N-atom donors; gold(I) remains in the form of linear dicyanidoaurate(I) ions. The extended structure consists of layers in which the AuI atoms form chains parallel to the short a axis, with Au...Au contacts of 3.7286 (1) Å, whereas the chains of potassium ions, which are also parallel to a, are bridged by bipyridyl and dicyanidoaurate residues. The analogous 1,10-phenanthroline adduct, namely poly[di-μ3-cyanido-κ6C:N:N-(μ2-1,10-phenanthroline-κ3N,N':N)gold(I)potassium(I)], [AuK(CN)2(C12H8N2)]n, (2), crystallizes as nonmerohedral twins in the space group C2/c. The packing is closely related to that of (1), but the chains are now parallel to the short b axis and the layers are parallel to (10\overline{1}). The two independent AuI atoms occupy special positions on inversion centres and twofold axes; the Au...Au contacts are 3.6771 (2) Å.

Lanthanum dithiocarbamates as potential extreme pressure lubrication additives

The extreme pressure lubrication (EPL) properties of bipyridyl adducts of different lanthanum dithiocarbamates of the type LaL3·bipy (where LH = dimethyl dithiocarbamate (Me2DTCH), piperidine dithiocarbamate (PipDTCH), morpholine dithiocarbamate (MorphDTCH), and diphenyl dithiocarbamate (Ph2DTCH); bipy = 2,2′-bipyridyl) have been evaluated with a four-ball lubricant tester using steel balls of 12.7-mm diameter and molybdenum disulfide as a reference additive. Various tribological parameters, viz. mean wear scar diameter, friction coefficient, mean specific pressure, initial seizure load, 2.5-s seizure delay load, weld load, flash temperature parameter, mean Hertz load, pressure wear index, etc., have been determined. The surface topography of wear scar has been studied by atomic force microscopy and scanning electron microscopy. Energy-dispersive X-ray analysis has been performed to give the composition of the wear scar surface. Experimental results indicate that admixtures containing bipyridyl adducts of lanthanum dithiocarbamates in paraffin oil exhibit better EPL properties than paraffin oil alone or with a reference additive (MoS2). In view of very high efficiency, the synthesized compounds can be recommended for their application as EPL additives.

Synthesis, spectral and thermal studies of 2,2′-bipyridyl adducts of bis(N-alkyl-N-phenyldithiocarbamato)zinc(II)

Three Zn(II) adducts of N-alkyl-N-phenyl dithiocarbamate with 2,2′-bipyridine have been synthesized and characterized by elemental analysis and spectroscopic techniques. The compounds are formulated as [Zn(mpdtc) 2bpy] ( 1), [Zn(epdtc) 2bpy] ( 2), and [Zn(bpdtc) 2bpy] ( 3) (where m = methyl, e = ethyl, b = butyl; p = phenyl and bpy = 2,2′-bipyridine). The single crystal X-ray structures of compounds ( 1) and ( 2) are also reported. It revealed that compound ( 1) exists as a five coordinate trigonal bipyramidal structures in which one dithiocarbamate acts as a chelating ligand and the other occupying the apical position acts as a monodentate ligand, while compound ( 2) exists as six coordinate octahedral species. Each of the two compounds has four molecules in the unit cell with the uncoordinated S atom in complex 1 involved in a weak C–H⋯S interaction. The thermal decomposition profiles of the compounds are also reported.

Synthesis, characterization and spectral studies of nitrogen base adducts of bis(O,O′-ditolyldithiophosphato)nickel(II). Crystal structures of Ni[S2P(OC6H4Me-p)2]2 · C10H8N2 and Ni[S2P(OC6H4Me-o)2]2 · C14H12N2 · C6H6

Reactions of Ni[S2P(OR)2]2(R=o-, m- and p-C6H4Me) with nitrogen donor ligands, viz. pyridine (C5H5N or py), 2,2′-bipyridyl (C10H8N2 or bipy) and 2,9-dimethyl-1,10-phenanthroline (C14H12N2 or dmphen) were carried out in benzene to yield green paramagnetic solids. These adducts were characterized by UV–visible and IR spectroscopy, magnetic measurements and, in two cases, by X-ray crystallography, to indicate how the number of donor atoms and steric factors affect the Ni–S bonding. The molecular structures of 2,2′-bipyridylbis {O,O′-di(p-tolyl)dithiophosphate}nickel(II), Ni[S2P(OC6H4Me-p)2]2·C10H8N2 and 2,9-dimethyl-1,10-phenanthrolinebis{O,O′-di(o-tolyl)dithiophosphate}nickel(II), Ni[S2P(OC6H4Me-o)2]2·C14H12N2·C6H6 are described. The geometry around nickel in the bipyridyl adduct is distorted octahedral with NiS4N2 coordination, whereas in the 2,9-dimethyl-1,10-phenanthroline adduct it is trigonal bipyramidal with NiS3N2 coordination in which one dithiophosphate moiety is bidentate and the other is monodentate.

4,4′-Bipyridyl adduct of an iodoantimonate anion linked by a 4,4′-bipyridinium cation

The crystal structure of the title iodo­bismuthate complex, 4,4′-bipyridinium(2+) di-μ-iodo-bis­[(4,4′-bipyridyl)­tri­iodo­bis­muth(III)], formulated as [4,4′-H2bipy]2+[Bi2I8(4,4′-bipy)2]2− or (C10H10N2)[Bi2I8(C10H8N2)2], has been determined. The compound is isostructural with its antimony analogue, each containing layers of hydrogen-bonded ribbon polymers in which anionic dinuclear complexes are linked through hydrogen bonding with 4,4′-H2bipy cations.

4,4′-Bipyridyl adduct of an iodobismuthate anion linked by a 4,4′-bipyridinium cation

The crystal structure of the title iodo­bismuthate complex, 4,4′-bipyridinium(2+) di-μ-iodo-bis­[(4,4′-bipyridyl)­tri­iodo­bis­muth(III)], formulated as [4,4′-H2bipy]2+[Bi2I8(4,4′-bipy)2]2− or (C10H10N2)[Bi2I8(C10H8N2)2], has been determined. The compound is isostructural with its antimony analogue, each containing layers of hydrogen-bonded ribbon polymers in which anionic dinuclear complexes are linked through hydrogen bonding with 4,4′-H2bipy cations.

Phosphonopropionic acid as a building block in supramolecular chemistry: salts with organic diamines.

The structures of seven salts formed by phosphonopropionic acid with organic diamines are reported; in these salts, the hydrogen-bonded substructures formed by the anions can be zero-, one- or two-dimensional, while the overall hydrogen-bonded supramolecular structures are three-dimensional. The 1:1 adduct, compound (1), formed between 1,2-bis(4'-pyridyl)ethene and phosphonopropionic acid is a salt, [[(C(12)H(10)N(2))H(2)](2+)].[(C(12)H(10)N(2))].[(C(3)H(6)O(5)P)(-)](2), in which both diamine components lie across centres of inversion in space group P2(1)/c. The anions form hydrogen-bonded head-to-head dimers, and these are linked by the two diamine units into sheets, which are themselves linked by C-H.O hydrogen bonds. With 2,2'-dipyridylamine the acid forms the hydrated salt [[(C(10)H(9)N(3))H](+)].[(C(3)H(6)O(5)P)(-)].H(2)O (2), in which all components are disordered with occupancy 0.5 in space group Fmm2. The anions form head-to-tail dimers, which are linked into sheets by the cations, and the sheets are linked into a three-dimensional framework by the water molecules. The piperazine salt [[(C(4)H(10)N(2))H(2)](2+)].[(C(3)H(5)O(5)P)(2-)] (3) contains simple anion chains linked into a three-dimensional framework by the two independent cations, both of which are centrosymmetric. In the hydrated salt formed by N,N'-dimethylpiperazine, [[(MeNC(4)H(8)NMe)H(2)](2+)].[(C(3)H(6)O(5)P)(-)](2).(H(2)O)(2) (4), head-to-tail anion chains combine with the water molecules to form a three-dimensional framework, which encloses voids that contain the cations. In the 4,4'-bipyridyl adduct [[(C(10)H(8)N(2))H(0.72)](0.72+)].[[(H(0.5)O)(3)PCH(2)CH(2)COOH(0.78)](0.72-)] (5), there is extensive disorder of the H atoms that are bonded to N and O atoms, and the anion chains are linked by the cations into sheets, which are themselves linked by C-H.O hydrogen bonds. In the 1:2 adduct formed with 1,2-bis(4'-pyridyl)ethane, [[(C(12)H(12)N(2))H(2)](2+)].[(C(3)H(6)O(5)P)(-)](2) (6), where the cation lies across an inversion centre, the anions form molecular ladders. These ladders are linked into sheets by the cations, which are themselves linked by C-H.O hydrogen bonds. In the methanol-solvated salt formed with 2,6-dimethylpiperazine, [[(C(6)H(14)N(2))H(2)](2+)].[(C(3)H(6)O(5)P)(-)](2). (CH(4)O)(0.34) (7), the anions form sheets that are linked into a three-dimensional framework by the cations. The supramolecular structures are compared with those of analogous salts formed by phosphonoacetic acid.

Di‐ and Trivalent Ytterbium Complexes Containing Linked Amino‐ and Amidocyclopentadienyl Ligands

AbstractReactions of the aminocyclopentadienes (C5Me4H)SiMe2NHR (R = Et, allyl, nPr, tBu) with [YbI2(THF)2] in the presence of two equivalents of potassium 1,2‐diphenylethenide in THF at room temperature gave the diamagnetic half‐sandwich complexes [Yb(η5‐C5Me4SiMe2NHR)Ln(μ‐I)]2 (L = THF, n = 2, L = DME, n = 1). The tert‐butylamido derivative [Yb(η5‐C5Me4SiMe2NHtBu)(THF)2(μ‐I)]2 was characterized by X‐ray structural analysis as a dinuclear complex containing a nonchelating aminocyclopentadienyl ligand. Deprotonation of the aminocyclopentadiene (C5H4tBu)SiMe2NHtBu with two equivalents of potassium 1,2‐diphenylethenide in THF, followed by reaction with [YbI2(THF)2] at 60 °C, gave the trivalent ytterbium ate complex [K(DME)][Yb{(η5:η1‐C5H3tBu‐3)SiMe2NtBu}2]. A single crystal X‐ray diffraction study of this complex shows polymeric chains consisting of trivalent ytterbocene units with two chelating amidocyclopentadienyl ligands coordinated to potassium ions. Metalation of the aminoindene (C9H7)SiMe2NHtBu under the same conditions and treatment with [YbI2(THF)2] in THF at ambient temperature resulted in the formation of the divalent ytterbocene complex [Yb{η5‐(1‐C9H6)SiMe2NHtBu}2(THF)2]. The reaction of ytterbium naphthalenide [Yb(C10H8)(THF)2] with one equivalent of (C9H7)SiMe2NHtBu afforded the bis(indenyl) compound which was isolated as its 2,2′‐bipyridyl adduct [Yb{η5‐(1‐C9H6)SiMe2NHtBu}2(bipy)]. It was shown by single‐crystal structural analysis to exhibit a bent metallocene structure with noncoordinating amino side‐chains. The reaction of (C5Me4H)CH2SiMe2NHtBu, which contains a longer CH2SiMe2 bridge, with [Yb(C10H8)(THF)2] gave the complex [Li0.5][Yb(μ‐η5:η1‐C5Me4CH2SiMe2NtBu)(THF)2(μ‐I)0.5]. Single crystal X‐ray structure analysis revealed the presence of polymeric chains consisting of dinuclear iodo‐bridged [Yb(η5:η1‐C5Me4CH2SiMe2NtBu)] units with a chelating linked amidocyclopentadienyl ligand, intermolecularly bridged by lithium ions. The lithium ions are bonded in an η5‐manner to both units, forming a lithocene structure. When YbCl3 was reacted with Li2[(C5H3tBu‐3)SiMe2NCH2CH2X] (X = NMe2, OMe), heterobimetallic complexes Li[Yb{(η5:η1‐C5H3tBu‐3)SiMe2NCH2CH2X}2] with a helical metallocene structure were isolated. The single crystal structure analysis of one of the three possible diastereomers of Li{Yb[(η5:η1‐C5H3tBu‐3)SiMe2NCH2CH2NMe2]2}, viz. the thermodynamically stable (R,R)/(S,S) epimer was performed. When YbCl3 was reacted with one equivalent of Li2[(C5H3tBu‐3)SiMe2NCH2CH2NMe2] and reduced “in situ” with one equivalent of sodium 1,2‐diphenylethenide in THF, the ytterbium(II) metallocene complex [Li(THF)]2[Yb{(η5‐C5H3tBu‐3)SiMe2NH(CH2CH2NMe2)}2(μ‐Cl)2] was isolated, which exhibits a structure with the two amino functions coordinating to the lithium ions and the chloro ligands bridging both the lithium and ytterbium centers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Gallium(III) organophosphonate adducts with the bidentate amines 2,2′-bipyridyl and 1,10-phenanthroline

A number of gallium(III) organophosphonates form adducts with the bidentate amines 2,2′-bipyridyl and 1,10-phenanthroline. These adducts contain a 1:2:1 molar ratio of metal/phosphorus/amine and have the proposed formulations Ga(O 3PR)(O 2P(OH)R)(C 10H 8N 2)·H 2O and Ga(O 3PR)(O 2P(OH)R)(C 12H 8N 2)·H 2O (where R=CH 3, C 6H 5 and CH 2C 6H 5; C 10H 8N 2 is 2,2′-bipyridyl and C 12H 8N 2 is 1,10-phenanthroline). Unlike the parent gallium(III) organophosphonates, which conform to the general formula Ga(OH)(O 3PR)· xH 2O ( x=0 or 1), the amine adducts lack the hydroxo group, but contain the organophosphonate ligand in the partially as well as fully deprotonated forms. All compounds were isolated from aqueous solutions as monohydrates, with the exception of the bipyridyl adduct of gallium(III) phenylphosphonate, which is anhydrous. TGA measurements suggest that for the hydrates, the water molecule is not coordinated to the metal. The bipyridyl adducts of gallium(III) phenylphosphonate and gallium(III) methylphosphonate, like the parent gallium(III) organophosphonates, are very likely layered, as indicated by the powder XRD patterns. In contrast, the corresponding phenanthroline adducts are non-layered, and both the bipyridyl and phenanthroline adducts of gallium(III) benzylphosphonate are amorphous solids. FTIR, powder XRD, TGA, XPS, solid state 31P/ 13C MAS-NMR and BET surface area data are presented and discussed.

Sensitive dependence of the hydrogen-bonded assemblies in cyanuric acid–4,4′-bipyridyl adducts on the solvent and the structure of the parent acid

Cyanuric acid (CA) forms a 2:1 hydrogen-bonded adduct with 4,4′-bipyridyl (BP) when co-crystallized from a methanol solution and a 1:1 adduct from an aqueous solution. The sheet structure of the 2:1 adduct involves cyclic hydrogen bonds between the amide units of adjacent CA molecules and N–H⋯N bonds between CA and BP. The 1:1 adduct crystallized from water has a chain structure with single N–H⋯O hydrogen bonds between the adjacent CA molecules. The structures of these hydrogen-bonded assemblies bear a close resemblance to the structures of CA crystallized from the corresponding solvents. N-methylcyanuric acid (MCA) forms a chain structure with single N–H⋯O bonds between the adjacent MCA molecules. The 1:1 hydrogen-bonded adduct of MCA with BP, crystallized from methanol or water solution, retains the chain structure. The structural sensitivity of the hydrogen-bonded assemblies to the solvent of crystallization and the relation between the supramolecular assembly of the adduct and the parent structure of CA are noteworthy.

Examination of the effect of crystal packing forces on geometric parameters: a combined crystallographic and theoretical study of 2,2'-bipyridyl adducts of R2SnCl2

Crystal structure determinations on a series of R2SnCl2(bipy)[bipy is 2,2'-bipyridyl] compounds show that these adopt a common structural motif in the solid-state with the Sn-bound organic substituents occupying mutually trans positions in a distorted octahedral geometry. A comparison of the experimental Sn–Cl and Sn–N bond distances with the moderated (i.e. by changing the nature of R) Lewis acidities of the tin atoms shows a general correlation, i.e. longer distances with decreasing Lewis acidity, but with a relatively large spread of values. In order to examine the role of crystal packing effects on the derived geometric parameters, gas-phase structures for these compounds have been modeled employing ab initio molecular orbital theory. These calculations showed that within individual compounds the two Sn–Cl distances are equal as are the two Sn–N distances, in contrast to the solid-state results. Further, a better correlation between the Sn–Cl and Sn–N bond distances and the Lewis acidity of the tin atom was found. These key results are attributed to the influence of crystal packing forces on the geometric parameters about the tin center in the solid-state.

Crystal synthesis using secondary and dative coordinate bonding: 4,4'-bipyridyl adducts of arylbismuth dihalides

Reaction between BiX2Ph (X = Cl or I) and 4,4'-bipy afforded crystals of complexes trans-[BiX2Ph(4,4'-bipy)]n as solvates in which an anticipated combination of dative (Bi?bipy) and secondary bonding (Bi⋯X) leads to a controlled polymeric structure.

Mixed-ligand lanthanide complexes-IX NMR spectral study of the adducts of Ln(fod) 3 with 2,2′-bipyridyl and 1,10-phenanthroline

The proton magnetic resonance spectra of the adducts of Ln(fod) 3 with 2,2′-bipyridyl and 1,10-phenanthroline, where Ln = La, Lu, Pr, Nd, Sm, Eu and Yb, have been studied in solution. The chemical shifts recorded have been analysed for these complexes and are dipolar in origin. Shifts are larger for the bipyridyl adducts than the phenanthroline adducts.

Complexes of trimethylplatinum(IV) with butane-2,3-dione monoxime

The dimeric complex of butane-2,3-dione monoxime (Hbdm) with trimethylplatinum(IV), [{PtMe3(bdm)}2]1, and its pyridine (py) and 2,2′-bipyridyl (bipy) adducts [PtMe3(bdm)(py)] and [PtMe3(bdm)(bipy)], show three different configurations for the ionised monoxime ligand. Dimer 1 forms a fluxional solvated monomer in co-ordinating solvents. Its solution-state stereodynamics in CD3OD have been measured by two-dimensional exchange NMR spectroscopy and a ‘windscreen-wiper’ mechanism proposed which is novel in trimethylplatinum(IV) chemistry.

Paramagnetic resonance in bipyridyl adducts of copper(II) salicylhydroxamates

AbstractESR spectra of bipyridyl(Bipy) adducts of copper(II) salicylhydroxamates were obtained at room and liquid nitrogen temperatures in polycrystalline samples. The bonding ability of Bipy is discussed on the basis of N‐superhyperfine coupling (N‐Shf) while the magnitude of CuL bonding is discussed on the basis of ESR parameters. The room temperature magnetic moment values indicated tetragonal distortion. The nature of distortion is also discussed on the basis of N‐Shf coupling.

Dimeric complexes of trimethylplatinum(IV) with ethylacetoacetate, methylacetoacetate, dimethylmalonate and diethylmalonate, and their pyridine and 2,2′-bipyridyl adducts

An 1H NMR study of the complexes [PtMe 3(R 1COCHCOR 2)] 2 (R 1  CH 3, R 2  OCH 3 ( 1) and R 1 ; CH 3, R 2 ; OC 2H 5 ( 2), R 1 ; R 2 ; OCH 3 ( 3) and R 1 ; R 2 ; OC 2H 5 ( 4)) shows that in solution 1–4 are non-fluxional at ambient temperature, in contrast to the complexes with R 1 ; R 2  alkyl. Incorporation of alkoxy groups into the β-dicarbonyl ligand strengthens the PtC bridge bond. The 1:1 adducts of 1–4 with pyridine and 2,2′-bipyridyl contain bidentate (O,O′bonded) and monodentate (Cbonded) dicarbonyl ligands, respectively. A correlation between 2 j(Pt-CH) and 2 j(Pt-CH) for compounds with a trans (CH 3)-Pt-(CH) feature is demonstrated.

2,2′-Bipyridyl adducts of tungsten oxide fluorides: preparation and characterization of WOF4•bipy and WO2F2•bipy; crystal structure of WO2F2•bipy

WOF4•bipy was prepared from the reaction of WOF4 with 2,2′-bipyridyl (bipy) in the melt or in solution in CH2Cl2 or CH3CN.The adduct, which is not moisture-sensitive at room temperature, was characterized by elemental analysis, X-ray powder data, and vibrational spectroscopy. WOF4•bipy is almost insoluble in the usual organic solvents, and the species which were observed in CH2Cl2 or CH3CN by 1H NMR and Raman spectroscopy resulted from the dismutation of WOF4•bipy into WO2F2•bipy and WF6•bipy.This transformation in solution was revealed by the slow growing of crystals identified as WO2F2•bipy and by the 1H NMR spectrum which displayed lines assigned to the independently synthesized and characterized species WF6•bipy. Unlike the WOF4 adduct, the tungstyl adduct is moisture-sensitive, its crystal structure showed that the tungsten atom is surrounded by a very distorted octahedron of ligands with each nitrogen of the bipy ligand trans to one oxygen atom and the two fluorine atoms trans to each other. The space group, unit cell parameters, and R factor for C10H8F2N2O2W are as follows: monoclinic, P21/n (No. 14) (alternate setting of the standard space group P21/c), a = 8.637(1) Å, b = 13.823(2) Å, c = 9.526(2) Å, β = 109.98(2)°, V = 1068.8(6) Å3, Z = 4, and R = 0.044 for 806 (I > 3σ(I)) of 1471 total reflections and 94 parameters. Keywords: 2,2′-bipyridyl adducts, tungsten oxide tetrafluoride, tungsten dioxide difluoride.

The preparation and characterization of bis(2,2-dimethylpropyl)cadmium(II) and its 2,2′-bipyridyl adduct

The synthesis and characterization of the compound bis(2,2-dimethylpropyl)cadmium(II), {bis(neopentyl)cadmium(II)} and its 1:1 adduct with 2,2′-bipyridyl are reported. The alkyl is moderately volatile (vapour pressure ca 3 torr, 52°C) and may find application as a precursor for the deposition of cadmium-containing films by MOCVD.

2,2′-Bipyridyl adducts of fluorides and oxide fluorides of tungsten

The formation of adducts of the bidentate ligand 2,2′-bipyridyl (bipy) with fluorides and oxide fluorides of tungsten was investigated WOF4. bipy was prepared from the reaction of WOF4 with bipy in the melt or in solution in CH2Cl2 or CH3CN. The adduct, which is not moisture sensitive at room temperature, was characterized by elemental analysis, x-ray powder data and vibrational spectroscopy.The crystal structure of WO2F2.bipy which was formed in small amounts from slow solvent assisted reaction of WOF4.bipy was determined. The space group, unit cell parameters, and R factors are as follows : monoclinic, P2sol1n (No.14), a = 8.637(1) Å, b = 13.823(2) Å, c = 9.526(2) Å, β = 109.98(2)°, V = 1068.8 Å3, Z = 4, and R = 0.044.Results concerning the adducts which were obtained when WF6was used instead of WOF4 are also presented.

The synthesis of trans-(Me 3CO) 3WCCHCHCW(OCMe 3) 3, cis,cis-(Me 3CO) 3WCCHCHCCCHCHCW(OCMe 3) 3, and related metal-capped ene-ynes, and evaluation of them as catalysts for preparing polydiacetylenes

Reaction of 0.5 equiv. of trans-5-decene-3,7-diyne with W(CEt)(OCMe 3) 3 yields trans-(Me 3CO) 3WCCHCHCW(OCMe 3) 3 ( 2) via the intermediate trans-(Me 3CO) 3WCCHCHCCEt ( 1), while reaction of 1 equiv. of cis-5-decene-3,7-diyne with W(CEt)(OCMe 3) 3 yields cis,cis-(Me 3CO) 3WCCHCHCCCHCHCW(OCMe 3) 3 ( 4) via cis-(Me 3CO) 3WCCHCHCCEt ( 3). Reaction of additional cis- or trans-5-decene-3,7-diyne with either 2 and/or 4 results in decomposition. Bipyridyl adducts of related metal-capped oligomers have been prepared and are more stable, but they are too insoluble to serve as intermediates in polymerization reactions. Reaction of 0.5 equiv. of 1,4-dibutynylbenzene with W(CEt)(OCMe 3) 3 yields (Me 3CO) 3WC(1,4-C 6H 4)CW(OCMe 3), while reaction of 1 equiv. of 1,2-dipentynylbenzene with W(CEt)(OCMe 3) 3 yields (Me 3CO) 3WC(1,2-C 6H 4)CC(1,2-C 6H 4)CW(OCMe 3) 3. Addition of 4 or more equiv. of 1,4-dibutynyl- or 1,2-dipentynyl-benzene to W(CEt)(OCMe 3) 3 results in formation of a yellow intractable product in less than 50% yield. It appears that either instability or insolubility of the growing polymers in this general class will limit their utility as catalysts.