Monometallic Analogues Research Articles

Exposing the synergistic effect between copper and vanadium in AlPO-5 during the selective oxidation of propene

Vanadium and copper were co-deposited into the microporous AlPO-5 to obtain VCu:AlPO-5. The catalytic activity towards selective oxidation of propene with feed gas components C3H6:4 O2 show maximum yield of 3.9% at 400°C with 5.5% acrolein selectivity. The activity towards acrolein is clearly enhanced in VCu:AlPO-5, when compared to monometallic analogues V:APO-5 and Cu:APO-5. The synergism between vanadium and copper was investigated with in situ XAS at the V and Cu K-edge during cycling in reaction components (C3H6/O2). Vanadium is initially present as pentavalent square pyramidal V(5+) indirectly bonded to copper at 2.9Å as confirmed by EXAFS. Vanadium was gradually reduced by propene to obtain 30% V(4+) fraction in VCu:AlPO-5, coinciding with rapid reduction of Cu(II) to Cu(I) (60%). Reduction in propene is accompanied by a decrease in the average VO and CuO first shell multiplicities. Interestingly, acrolein is formed over VCu:AlPO-5 in propene only, but the activity decreases with time on stream. After switching to oxygen the activity is diminished and the local vanadium and copper surroundings are restored. Reduction of vanadium was not observed in V:AlPO-5, hence copper promotes the reducibility of vanadium and propene oxidation is activated by the dynamic nanoparticulate CuVOx/Cu(I)V(4+)Ox−1 species formed in AlPO-5.

Identification of synergistic Cu/V redox pair in VCu:AlPO-5; a comparison with VCu:ZSM-5.

Vanadium(V) and copper(II) were co-deposited into AlPO-5 and H-ZSM-5 three-dimensional microporous carriers to yield VCu:AlPO-5 and VCu:ZSM-5. The materials, along with copper analogues were tested for the selective oxidation of propene, and the catalysts perform in the following order: VCu:AlPO-5 > Cu:AlPO-5 > VCu:ZSM-5 > Cu:ZSM-5. Acrolein was selectively formed over VCu:AlPO-5 and Cu:AlPO-5 over a very wide range from 300 to 450 °C, whereas VCu:ZSM-5 displays a limited temperature window for acrolein formation (300-350 °C). Hence, the choice of carrier and presence of vanadium as a co-cation greatly affects the acrolein selectivity and activity window. The vanadium and copper reduction events were monitored by in situ X-ray Absorption Spectroscopy (XAS) during C3H6-TPR (1.11%) to 450 °C. The Cu(II)/(I) redox pair initiates reduction of V(V) → V(IV) in VCu:AlPO-5 and VCu:ZSM-5 at 375 °C. Metallic copper is the major valence fraction above 400 °C in both samples while vanadium is present as V(IV)/V(III) species. In the monometallic copper analogues Cu(I) is the major valence fraction above 350 °C, hence synergistic effects between the Cu/V pair causes hyper-reduction of copper. EXAFS shows that copper and vanadium are in close proximity in VCu:AlPO-5 only, being linked by bridging oxygens (Cu-O-V) believed to interact with propene. By contrast, propene adsorbs on Brønsted sites in VCu:ZSM-5 inhibiting acrolein formation at elevated temperatures, as confirmed by DRIFTS. We believe the reactive Cu/V pair in neutral AlPO-5 generates extralattice oxygens favouring acrolein formation over a wide temperature range.

Synthesis of Equimolar Pd–Ru Alloy Nanoparticles Incorporated Mesoporous Alumina Films: A High Performance Reusable Film Catalyst

We report the synthesis of equimolar Pd–Ru alloy nanoparticles (NPs) incorporated mesoporous alumina films (Pd–Ru/MAF) by the sol–gel route. The synthetic strategy involves homogeneous mixing of the Pd2+ and Ru3+ ions in the alumina sol containing P123 micelles. Dip-coated films, prepared on ordinary glass substrates, were thermally reduced at a relatively lower temperature (500 °C) to generate equimolar Pd–Ru/MAF with a nominal molar composition of Pd:Ru:AlO1.5 = 2:2:96. Electron microscopy studies revealed uniformly distributed Pd–Ru alloy NPs in a mesoporous alumina–alumina sphere composite film matrix. The P123/alumina nanocomposite acted as an excellent breeding medium to form Pd–Ru (∼1:1) alloy NPs despite the poor miscibility of the two metals. Pd–Ru/MAF showed excellent catalytic performances with highest normalized rate constant values (5.43 × 1014 min–1 mol–2) and possessed good reusability compared to the corresponding monometallic analogues in the reduction of aqueous 4-nitrophenol in the pres...

New modulated design, docking and synthesis of carbohydrate-conjugate heterobimetallic CuII–SnIV complex as potential topoisomerase II inhibitor: In vitro DNA binding, cleavage and cytotoxicity against human cancer cell lines

New carbohydrate-conjugate heterobimetallic complexes [C22H50N6O13CuSnCl2] (3) and [C22H58N6O17NiSnCl2] (4) were synthesized from their monometallic analogs [C22H52N6O13Cu] (1) and [C22H60N6O17Ni] (2) containing N-glycoside ligand (L). In vitro DNA binding studies of L and complexes (1–4) with CT DNA were carried out by employing various biophysical and molecular docking techniques which revealed that heterobimetallic complex 3 strongly binds to DNA in comparison to 4, monometallic complexes (1 and 2) and the free ligand. Complex 3 cleaves pBR322 DNA via hydrolytic pathway (confirmed by T4 DNA ligase assay) and inhibited Topo-II activity in a dose-dependent manner. Furthermore, complex 3 was docked into the ATPase domain of human-Topo-II in order to probe the possible mechanism of inhibition.

Experimental and DFT Characterization of Metal-to-Ligand Charge-Transfer Excited States of (Rutheniumammine)(Monodentate Aromatic Ligand) Chromophores

The heretofore unknown emission properties of the metal-to-ligand charge-transfer (MLCT) excited states of several complexes with (ruthenium)(monodentate aromatic ligand, MDA) chromophores are given. Emission spectra and lifetimes in 77 K glasses are reported for several monometallic complexes of the type [Ru(NH3)(5-n)(L)(n)(MDA)](2+) and two bimetallic pyrazine (pz)-bridged [{Ru(NH3)(4-n)(L)(n)}2pz](4+) complexes (L = pz, pyridine, or a multipyridine ligand; MDA = pz or a substituted pyridine, Y-py). The emission maxima occur in the visible and near-IR spectral regions and have much more poorly resolved vibronic sidebands than do related complexes with Ru-bpy chromophores, and the excited-state lifetimes are characteristic of Ru-bpy MLCT excited states in this energy range. The emission yields of trans-[Ru(NH3)4(MDA)(pz)](2+) (MDA = py or pz) are less than 0.2%, and combined with the other observations, this implies that most of the excited-state quenching occurs in high-energy excited states whose population precedes that of the lowest-energy (3)MLCT excited state. The pz-bridged, bimetallic complexes have mixed-valence excited states, and they absorb and emit at lower energies than their monometallic analogues do.

Cooperative Catalysis: Large Rate Enhancements with Bimetallic Rhodium Complexes

A large increase in reaction rate was observed for the catalyzed mono- and dihydroalkoxylation of alkynes when structurally constrained bimetallic Rh(I) catalysts with imidazolyl-imine ligands were compared to their monometallic analogues. The “cooperative” enhancement was vastly improved by restricting the conformational freedom of the bimetallic structure and minimizing the intermetallic Rh···Rh distance.

Pyracene‐Linked Bis‐Imidazolylidene Complexes of Palladium and Some Catalytic Benefits Produced by Bimetallic Catalysts

Two new palladium complexes with a pyracene-linked bis-imidazolylidene (pyrabim) group have been obtained and fully characterized. The related monometallic analogues were obtained from the coordination of an acetanaphthene-supported N-heterocyclic carbene (NHC). The catalytic properties of all complexes were studied in the acylation of aryl halides with hydrocinnamaldehyde, and in the Suzuki-Miyaura coupling of aryl halides and aryl boronic acids. The results show that the presence of a second metal in the dimetallic complexes induces some benefits in the catalytic behavior of the complexes. This effect is more pronounced in the Suzuki-Miyaura coupling, for which the dimetallic complexes exhibit significantly higher activity than their monometallic counterparts.

Probing the Characteristics of Mono- or Bimetallic (Iron or Cobalt) Complexes Bearing 2,4-Bis(6-iminopyridin-2-yl)-3H-benzazepines: Synthesis, Characterization, and Ethylene Reactivity

A series of 2,4-bis(6-iminopyridin-2-yl)-3H-benzazepines and the mono- or bimetallic (Fe2+ or Co2+) complexes thereof were synthesized and characterized. All title complexes, when activated by MAO or MMAO, exhibited high activities of up to 4.0 × 107 g (mol of Fe)−1 h–1 for ethylene oligomerization and polymerization. The iron(II) precatalysts generally showed higher activities and produced a wider distribution of products (including oligomers and polyethylene) than did their corresponding cobalt(II) analogues. The bimetallic precatalysts exhibited higher (almost twice) activities in comparison to their monometallic analogues. The distribution of the resulting oligomers closely resembled the Schultz–Flory rule.

Cooperative Assembly of Zn Cross-Linked Artificial Tripeptides with Pendant Hydroxyquinoline Ligands

An artificial peptide with three pendant hydroxyquinoline (hq) ligands on a palindromic backbone was designed and used to form multimetallic assemblies. Reaction of the tripeptide with zinc acetate led to a highly fluorescent tripeptide duplex with three Zn(II) coordinative cross-links. The binding process was monitored using spectrophotometric absorbance and emission titrations; NMR spectroscopy and mass spectrometry confirmed the identity and stoichiometry of the product structure. Titrations monitoring duplex formation of the zinc-tripeptide structure had a sigmoidal shape, equilibrium constant larger than the monomeric analogue, and a Hill coefficient >1, all of which indicate positive cooperativity. Photophysical characterization of the quantum yield, excited state lifetime, and polarization anisotropy are compared with the monometallic zinc-hq analogue. A higher than expected quantum yield for the trimetallic complex suggests a structure in which the central chromophore is shielded from solvent by π-stacking with neighboring Zn(II) complexes.

Are Metal–Metal Interactions Involved in the Rising Enthalpies Observed in The Kubas Binding of H2 to Hydrazine-Linked Hydrogen Storage Materials?

Models of two linked M(III) and M(II) (M = Ti, V, Cr) binding sites in hydrazine-linked hydrogen storage materials have been studied quantum chemically using density functional theory. The results compare favorably with previous experimental and computational results. Strong evidence is observed that the H2 molecules bind to the metal in a Kubas manner. As seen previously in monometallic analogues,(1, 2) altering the transition metal across the first row of the periodic table reduces the number of H2 molecules that can be bound, and replacing a hydrazide ligand with a hydride increases the M-H2 interaction energy. Evidence is presented for metal–metal interactions, which can influence the H2 binding enthalpy and may help to explain the observed metallic properties and rising H2 binding enthalpies with coverage of the experimental materials. An alternate explanation for the rising enthalpies is also proposed, involving a pressure-induced deformation of the structure with concomitant twisting of the bonds i...

RuxPtySnzcluster-derived nanoparticlecatalysts: spectroscopic investigation into the nature of active multinuclear single sites

Cluster-derived Ru(x)Pt(y)Sn(z) nanoparticles are active catalysts in the hydrogenation of nitrobenzene. The nature of the active sites has been elucidated by FTIR spectroscopy using CO and NO as probe molecules. A new metal carbonyl cluster precursor, Pt(2)Ru(2)(SnBu(t)(3))(2)(CO)(9)(μ-H)(2), has been synthesized to obtain a Ru(2)Pt(2)Sn(2)/SiO(2) catalyst, that displayed remarkably high levels of conversion and selectivities compared to other bi-and monometallic analogues. Spectroscopic comparisons with Ru(5)PtSn/SiO(2) indicate that both the nature and the stoichiometry of the metals play a key role in modulating the catalytic activities and selectivities. A multinuclear single-site containing Pt centers, which facilitate the hydrogen activation, coupled with a highly reactive Ru site, possibly involved in the nitrobenzene activation, can be hypothesized. The oxophilicity of tin helps with the anchoring of the nanoparticles, aids the dispersion of the other metals, and can play an important role in influencing the selectivity to aniline.

Engineering active sites for enhancing synergy in heterogeneous catalytic oxidations

The simultaneous isomorphous substitution of Al(III) and P(V) ions, in an aluminophosphate framework, with redox active Co(III) and Ti(IV) metal ions, generates highly active single-site heterogeneous catalysts that exhibit considerable synergy, compared to their corresponding monometallic analogues, in the catalytic epoxidation of olefins.

A Phenomenological Study on the Synergistic Role of Precious Metals in the Steam Reforming of Logistic Fuels on Bimetal-Supported Catalysts

Fuel processors are required to convert sulfur-laden logistic fuels into hydrogen-rich reformate and deliver to the fuel cell stack with little or no sulfur. Since sulfur poisons and deactivates the reforming catalyst, robust sulfur-tolerant catalysts ought to be developed. In this paper, the development, characterization and evaluation of a series of reforming catalysts containing two noble metals (with total metal loading not exceeding 1 weight percent) supported on nanoscale ceria for the steam-reforming of kerosene is reported. Due to inherent synergy, a bimetallic catalyst is superior to its monometallic analog, for the same level of loading. The choice of noble metal combination in the bimetallic formulations plays a vital and meaningful role in their performance. Presence of ruthenium and/or rhodium in formulations containing palladium showed improved sulfur tolerance and significant enhancement in their catalytic activity and stability. Rhodium was responsible for higher hydrogen yields in the logistic fuel reformate. Duration of steady hydrogen production was higher in the case of RhPd (75 h) than for RuPd (68 h); hydrogen generation was stable over the longest period (88 h) with RuRh containing no Pd. A mechanistic correlation between the characteristic role of precious metals in the presence of each other is discussed.

Development of Bimetallic Titanocene−Ruthenium−Arene Complexes As Anticancer Agents: Relationships between Structural and Biological Properties

A series of bimetallic titanium-ruthenium complexes of general formula [(η(5)-C(5)H(5))(μ-η(5):κ(1)-C(5)H(4)(CR(2))(n)PR'R'')TiCl(2)](η(6)-p-cymene)RuCl(2) (n = 0, 1, 2 or 4; R = H or Me; R' = H, Ph, or Cy; R'' = Ph or Cy) have been synthesized, including two novel compounds as well as two cationic derivatives of formula [(η(5)-C(5)H(5))(μ-η(5):κ(1)-C(5)H(4)(CH(2))(n)PPh(2))TiCl(2)] [(η(6)-p-cymene)RuCl](BF(4)) (n = 0 or 2). The solid state structure of two of these compounds was also established by X-ray crystallography. The complexes showed a cytotoxic effect on human ovarian cancer cells and were markedly more active than their Ti or Ru monometallic analogues titanocene dichloride and RAPTA-C, respectively. Studies of cathepsin B inhibition, an enzyme involved in cancer progression, showed that enzyme inhibition by the bimetallic complexes is influenced by the length of the alkyl chain in between the metal centers. Complementary ESI-MS studies provided evidence for binding of a Ru(II) fragment to proteins.

Mixed d−f3 Coordination Complexes Possessing Improved Near-Infrared (NIR) Lanthanide Luminescent Properties in Aqueous Solution

The cyclen-based ligand 1, possessing a [1,10]-phenanthroline moiety as a pendant arm, has been used as a ditopic ligand for the complexation of d- and near infrared (NIR) emitting (and) f-metal ions. This ligand forms kinetically stable complexes, 1·Ln, with lanthanide ions such as Ln = ytterbium, neodymium, and lutetium (formed as a non-IR emitting reference compound), the synthesis and photophysical properties of which are described herein in detail. These 1·Ln complexes were then used as building blocks for the formation of mixed d−f heteropolymetallic self-assemblies, where the phen moiety was used to complex a ruthenium (Ru(II)) ion, giving the d−f3 complexes Ru·Ln3 (Ln = Nd(III), Yb(III), Lu(III)). The formation of these supramolecular coordination conjugates was studied by using absorption and luminescence spectroscopy, while the solution structure of the Ru·Lu3 was elucidated by 1H NMR in D2O and H2O. Of these conjugates, both Ru·Nd3 and Ru·Yb3 displayed an intense NIR-emission in H2O at pH 7.4 (with Q(Yb)(L) = 0.073% and Q(Nd)(L) = 0.040%) and in D2O (with QYbL = 0.23% and Q(Nd)(L) = 0.10%). By comparison with their monometallic analogues Ln·1 (Ln = Nd(III), Yb(III)), we demonstrate that our new design possesses an enhanced sensitization efficiency for lanthanide metal centered sensitization upon using the [Ru(phen)3] moiety (d → f energy transfer) as a visibly exciting antenna, and we demonstrate that the intensity of the Ru(II)-based luminescence strictly correlates to the efficiency of the d → f energy transfer processes.

Bimetallic Mesoflowers: Region-Specific Overgrowth and Substrate Dependent Surface-Enhanced Raman Scattering at Single Particle Level

A strategy for the preparation of bimetallic mesoflowers (MFs) has been demonstrated by a simple overgrowth reaction. We make hybrid MFs containing Au core and shells of different metals, such as Ag and Pt, by tuning the experimental conditions so as to study region-specific overgrowth. This selective growth is attributed to the specific binding affinity of cetyltrimethylammonium bromide (CTAB) at different crystal planes of Au MF surfaces. We also studied the region-specific, composition dependent surface-enhanced Raman scattering (SERS) activity of single bimetallic MFs to understand their chemical environment. Substrate effects on the SERS activity at single particle level were evaluated by a comparative study of the Raman images of Au, Au/Ag, and Au/Pt MFs. Region-specific SERS activity exhibited by single Au/Ag MF provides an insight into the SERS activity of bimetallic MFs over their monometallic analogues.

Synthesis, Structures, Bonding, and Redox Chemistry of Ditungsten Butadiyne Complexes with W≡C—C≡W Backbones

Complexes of the form XL(4)W[triple bond]C-C[triple bond]WL(4)X (L = 1/2 dmpe, 1/2 depe, P(OMe)(3); X = Cl, OTf) have been synthesized from (Bu(t)O)(3)WCCW(OBu(t))(3) in two steps via Cl(3)(dme)WCCW(dme)Cl(3), which undergoes facile four-electron reduction in the presence of L. The compounds possess formal d(2)-d(2) electron configurations. The molecular structures of Cl(dmpe)(2)WCCW(dmpe)(2)Cl and Cl{P(OMe)(3)}(4)WCCW{P(OMe)(3)}(4)Cl were determined by X-ray crystallography; bond distances within the backbone are consistent with a W[triple bond]C-C[triple bond]W canonical structure. Density-functional-theory calculations on Cl(dmpe)(2)WCCW(dmpe)(2)Cl and the model compound Cl(PH(3))(4)WCCW(PH(3))(4)Cl, and on their monometallic analogs W(CH)(dmpe)(2)Cl and W(CH)(PH(3))(4)Cl, indicate that the WCCW backbone is strongly pi-conjugated; this is supported by the observation of low-energy pi --> pi* transitions for the compounds. The calculations predict that delta symmetry d(xy)-derived orbitals should be (or lie near) the highest occupied molecular orbital. Consistent with this prediction, the electronic spectra of the compounds exhibit a band attributable to d(xy) --> pi* transition(s), as the lowest-energy feature and electrochemical studies demonstrate that they undergo sequential one-electron oxidations to produce (d(xy))(2)-(d(xy))(1) and (d(xy))(1)-(d(xy))(1) congeners. Due to the delta symmetry of the redox orbitals, the oxidized congeners maintain the W[triple bond]C-C[triple bond]W canonical structure of the parent d(2)-d(2) compounds. The first and second oxidation potentials of Cl(dmpe)(2)WCCW(dmpe)(2)Cl are separated by <or=0.4 V, corresponding to K(com) = 10(4)-10(6); the interaction between redox orbitals is largely electrostatic in origin and not the result of significant direct delta orbital overlap. The reaction between Cl(dmpe)(2)WCCW(dmpe)(2)Cl and HCl (2 equiv) produces the d(0)-d(0) dihydride ion [Cl(H)(dmpe)(2)WCCW(dmpe)(2)(H)Cl](2+), which is formulated as maintaining the W[triple bond]C-C[triple bond]W backbone on the basis of its X-ray crystal structure and NMR spectra. This family of WCCW derivatives expands the relatively small class of M[triple bond]C-C[triple bond]M compounds and is distinctive among them because their ancillary ligands should allow incorporation of the L(4)WCCWL(4) unit into interior positions of metalloyne oligomers and polymers.

Synthesis, characterization and DNA-binding studies of mono and heterobimetallic complexes Cu[sbnd]Sn2/Zn[sbnd]Sn2 and their DNA cleavage activity

Heterobimetallic complexes C6H24N4O6CuSn2Cl63, C6H24N4O6ZnSn2Cl64 have been synthesized from their monometallic analogs C6H16N4O2CuCl21, C6H16N4O2ZnCl22, and were characterized by various spectroscopic and analytical methods. The complexes 1–4 reveal an octahedral geometry for both central metal ions Cu/Zn as well as for Sn metal ion. The interaction of complexes 1–4 with CT-DNA, were investigated by using absorption, emission, cyclic voltammetry, viscometry and DNA cleavage studies. The emission quenching of 3 and 4 by [Fe(CN)6]4− depressed greatly when bound to CT-DNA. The results of spectroscopic, viscometric and cyclic voltammetry of complexes 3 and 4 revealed electrostatic mode of binding of the complexes with CT-DNA. These results revealed that 4 bind more avidly in comparison to 3 with CT-DNA. Gel electrophoresis of DNA with complexes 3 and 4 demonstrated that the complexes exhibit excellent cleavage activity under physiological conditions.

Bimetallic N-Heterocyclic Carbene−Iridium Complexes: Investigating Metal−Metal and Metal−Ligand Communication via Electrochemistry and Phosphorescence Spectroscopy

Bimetallic [Ir(COD)Cl] and [Ir(ppy)(2)] (COD = 1,5-cyclooctadiene; ppy = 2-phenylpyridyl) complexes bridged by 1,7-dimethyl-3,5-diphenylbenzobis(imidazolylidene) (1), in addition to their monometallic analogues supported by 1-methyl-3-phenylbenzimidazolylidene (2), were synthesized and studied. Electrochemical analyses indicated that 1 facilitated moderate electronic coupling between [Ir(COD)Cl] units (DeltaE = approximately 60 mV), but not [Ir(ppy)(2)]. The metal-based oxidation potentials for the bimetallic complexes were within 20 mV of those for their monometallic analogues. Furthermore, spectroscopic analyses of the [Ir(ppy)(2)] bimetallic and monometallic complexes revealed nearly identical phosphorescence profiles, indicating that carbene coordination does not affect the energy of the emissive states. Collectively, these results suggest that N-heterocyclic carbenes (NHCs) such as 1 could link together two emissive fragments without altering their fundamental phosphorescence profiles. Ultimately, employing multitopic NHCs as non-interfering molecular connectors could facilitate the rational design of new phosphorescent materials as well as second-generation phosphor dopants.

Bimetallic Effects for Enhanced Polar Comonomer Enchainment Selectivity in Catalytic Ethylene Polymerization

The synthesis and characterization of the bimetallic 2,7-di-[(2,6-diisopropylphenyl)imino]-1,8-naphthalenediolato group 10 metal polymerization catalysts {[Ni(CH(3))](2)[1,8-(O)(2)C(10)H(4)-2,7-[CH=N(2,6-(i)Pr(2)C(6)H(3))](PMe(3))(2)} and {[Ni(1-naphthyl)](2)[1,8-(O)(2)C(10)H(4)-2,7-[CH=N(2,6-(i)Pr(2)C(6)H(3))](PPh(3))(2)} [FI(2)-Ni(2)(PR(3))(2)] are presented, along with the synthesis and characterization of the mononuclear analogues {Ni(CH(3))[3-(t)Bu-2-(O)C(6)H(3)CH=N(2,6-(i)Pr(2)C(6)H(3))](PMe)(3)} and {Ni(1-naphthyl)[3-(t)Bu-2-(O)C(6)H(3)CH=N(2,6-(i)Pr(2)C(6)H(3))](PPh)(3)} [FI-Ni (PR(3))]. Monometallic Ni catalysts were also prepared by functionalizing one ligation center of the bimetallic ligand with a trimethylsilyl group (TMS), yielding {Ni(CH(3))[1,8-(O)(TMSO)C(10)H(4)-2,7-[CH=N(2,6-(i)Pr(2)C(6)H(3))](PMe(3))} [TMS-FI(2)-Ni(PMe(3))]. The FI(2)-Ni(2) catalysts exhibit significant increases in ethylene homopolymerization activity versus the monometallic analogues, as well as increased branching and methyl branch selectivity, even in the absence of a Ni(cod)(2) cocatalyst. Increasing ethylene concentrations significantly suppress branching and alter branch morphology. FI(2)-Ni(2)-mediated copolymerizations with ethylene + polar-functionalized norbornenes exhibit a 4-fold increase in comonomer incorporation versus FI-Ni, yielding copolymers with up to 10% norbornene copolymer incorporation. FI(2)-Ni(2)-catalyzed copolymerizations with ethylene + methylacrylate or methyl methacrylate incorporate up to 11% acrylate comonomer, while the corresponding mononuclear FI-Ni catalysts incorporate negligible amounts. Furthermore, the FI(2)-Ni(2)-mediated polymerizations exhibit appreciable polar solvent tolerance, turning over in the presence of ethyl ether, acetone, and even water. The mechanism by which the present cooperative effects take place is investigated, as is the nature of the copolymer microstructures produced.