Bis[mu-N-(2,6-dimethylphenyl)acetamidato]-bis(dimethylaluminium)

The structure of the title compound, [Al2(CH3)4(C10H12NO)2] or [Me2Al{[mu]-(2,6-Me2C6H3)NCMeO}]2, consists of a four-coordinate dimeric centrosymmetric eight-membered ring Al-containing species

Bis[μ-N-(2,6-dimethylphenyl)acetamidato]-bis(dimethylaluminium)

The structure of the title compound, [Al2(CH3)4(C10H12NO)2] or [Me2Al{[mu]-(2,6-Me2C6H3)NCMeO}]2, consists of a four-coordinate dimeric centrosymmetric eight-membered ring Al-containing species

Bis(iminopyridyl)phthalazine as a sterically hindered compartmental ligand for an M-2 (M = Co, Ni, Fe, Zn) centre; Applications in ethylene oligomerisation

The new bis(iminopyridyl)phthalazine ligand, 1,4-{(2,6-i-Pr2C6H3)Ndouble bond; length as m-dashCMe)C5H3N}2C8H4N2 (L), has been prepared in good yield using a combination of palladium-mediated cross coupling and condensation strategies. Reaction of L with three equivalents of CoX2 (X = Cl, Br) in n-BuOH at elevated temperature generates, on crystallisation from bench acetonitrile, the paramagnetic tetrahalocobaltate salts [(L)Co2X(μ-X)(NCMe)m(OH2)n](CoX4) (X = Cl, m = 2, n = 1 1a; X = Br, m = 2, n = 0 1b) as acetonitrile or mixed acetonitrile/aqua adducts; a similar product is obtained from the reaction of FeCl2 with L and has been tentatively assigned as [(L)Fe2Cl(μ-Cl)(OH2)3](FeCl4) (2). By contrast, reaction of L with NiX2(DME) (X = Cl, Br; DME = 1,2-dimethoxyethane), under similar reaction conditions, affords the halide salts [(L)Ni2X2(μ-X)(OH2)2](X) (X = Cl 3a, X = Br 3b) as aqua adducts. Structural determinations on 1 and 3 reveal L to adopt a bis(tridentate) bonding mode allowing the halide-bridged metal centres to assemble in close proximity (M⋯M range: 3.437–3.596 Å). Unexpectedly, on reaction of L with ZnCl2, the neutral bimetallic [(L)Zn2Cl4] (4b) complex is formed in which the ZnCl2 units fill inequivalent binding sites within L (viz. the Nphth,Npy,Nim and Npy,Nim pockets). Complex 4b could also be obtained by the sequential addition of ZnCl2 to L to form firstly monometallic [(L)ZnCl2] (4a) and then on further ZnCl2 addition 4b; the fluxional behaviour of diamagnetic 4a and 4b is also reported. On activation with excess methylaluminoxane (MAO), 1–3 display modest activities for ethylene oligomerisation forming low molecular weight waxes with methyl-branched products predominating for the nickel systems (3). On the other hand, the iron catalyst (2) gives exclusively α-olefins while the cobalt systems (1) are much less selective affording equal mixtures of α-olefins and internal olefins along with lower levels of vinylidenes and tri-substituted alkenes. Single crystal X-ray structures are reported for L, 1a, 1b, 3a, 3b and 4

Crystal structure of (aceto-nitrile-κN)iodido-(2-(naphthalen-1-yl)-6-{1-[(2,4,6-tri-methyl-phen-yl)imino]ethyl}-pyridine-κ(2)N,N')copper(I).

In the mononuclear title complex, [CuI(C2H3N)(C26H24N2)], the Cu(I) ion has a distorted tetra-hedral coordination environment, defined by two N atoms of the chelating 2-(naphthalen-1-yl)-6-[(2,4,6-tri-methyl-phen-yl)imino]-pyridine ligand, one N atom of an aceto-nitrile ligand and one iodide ligand. Within the complex, there are weak intra-molecular C-H⋯N hydrogen bonds, while weak inter-molecular C-H⋯I inter-actions between complex mol-ecules, help to facilitate a three-dimensional network

Substituted N-picolylethylenediamines of the type (ArNHCH[subscript 2]CH[subscript 2]){(2-C[subscript 5]H[subscript 4]N)CH[subscript 2]}NR [R = Me, 4-CH[subscript 2]=CH(C[subscript 6]H[subscript 4])CH[subscript 2], (2-C[subscript 5]H[subscript 4]N)CH[subscript 2]] and their transition metal(II) halide complexes

Alkylation of (ArNHCH[subscript 2]CH[subscript 2]){(2-C[subscript 5]H[4]N)CH[subscript 2]}NH with RX [RX = MeI, 4-CH[subscript 2]=CH(C[subscript 6]H[subscript 4])CH[subscript 2]Cl) and (2-C[subscript 5]H[subscript 5]N)CH[subscript 2]Cl] in the presence of base has allowed access to the sterically demanding multidentate nitrogen donor ligands, {(2,4,6-Me[subscript 3]C[subscript 6]H[subscript 2])NHCH[subscript 2]CH[subscript 2]}{(2-C[subscript 5]H[subscript 4]N)CH[subscript 2]}NMe (L1), {(2,6-Me[subscript 3]C[subscript 6]H[subscript 3])NHCH[subscript 2]CH[subscript 2]}{(2-C[subscript 5]H[subscript ]4N)CH[subscript 2]}NCH[subscript 2](C[subscript 6]H[subscript 4])-4-CH=CH[subscript 2] (L2) and (ArNHCH[subscript 2]CH[subscript 2]){(2-C[subscript 5]H[subscript 4]N)CH[subscript 2]}[subscript 2]N (Ar = 2,4-Me[subscript 2]C[subscript 6]H[subscript 3] L3a, 2,6-Me[subscript 2]C[subscript 6]H[subscript 3]L3b) in moderate yield. L3 can also be prepared in higher yield by the reaction of (NH[subscript 2]CH[subscript 2]CH[subscript 2]){(2-C[subscript 5]H[subscript 4]N)CH[subscript 2]}[subscript 2]N with the corresponding aryl bromide in the presence of base and a palladium(0) catalyst. Treatment of L1 or L2 with MCl[subscript 2] [MCl[subscript 2] = CoCl[subscript 2]·6H[subscript 2]O or FeCl[subscript 2](THF)[subscript 1.5]] in THF affords the high spin complexes [(L1)MCl[subscript 2]] (M = Co 1a, Fe 1b) and [(L2)MCl[subscript 2]] (M = Co 2a, Fe 2b) in good yield, respectively; the molecular structure of 1a reveals a five-coordinate metal centre with L1 bound in a facial fashion. The six-coordinate complexes, [(L3a)MCl[subscript 2]] (M = Co 3a, Fe 3b, Mn 3c) are accessible on treatment of tripodal L3a with MCl[subscript 2]. In contrast, the reaction with the more sterically encumbered L3b leads to the pseudo-five-coordinate species [(L3b)MCl[subscript 2]] (M = Co 4a, Fe 4b) and, in the case of manganese, dimeric [(L3b)MnCl(µ-Cl)][subscript 2] (4c); in 4a and 4b the aryl-substituted amine arm forms a partial interaction with the metal centre while in 4c the arm is pendant. The single crystal X-ray structures of 1a, 3b·MeCN, 3c·MeCN, 4b·MeCN and 4c are described as are the solution state properties of 3b and 4b

Resonance Raman spectroscopy as an in situ probe for monitoring catalytic events in a Ru–porphyrin mediated amination reaction

Resonance Raman microspectroscopy has been widely used to study the structure and dynamics of porphyrins and metal complexes containing the porphyrin ligand. Here, we have demonstrated that the same technique can be adapted to examine the mechanism of a homogeneously-catalysed reaction mediated by a transition-metal-porphyrin complex. Previously it has been challenging to study this type of reaction using in situ spectroscopic monitoring due to the low stability of the reaction intermediates and elevated-temperature conditions. We have made a straightforward modification to the sample stage on a microscope for time-lapsed Raman microspectroscopy from reaction mixtures in these media. The allylic amination of unsaturated hydrocarbons by aryl azides, which can be catalysed by a ruthenium-porphyrin complex, has been used as an illustrative example of the methodology. The mechanism of this particular reaction has been studied previously using density-functional theory and kinetic approaches. The Raman measurements support the mechanism proposed in the earlier publications by providing the first experimental verification of a precursor reaction complex between the aryl azide and the ruthenium metal ion, and evidence for the formation of a mono-imido intermediate complex under conditions of high concentration of the reactant olefin

Developments in compartmentalized bimetallic transition metal ethylene polymerization catalysts

Recent progress concerning the application of compartmentalized bimetallic complexes as homogeneous catalysts in ethylene polymerization is reviewed with particular regard to metal-metal combinations based on either early- (Ti, Zr, Hf and V) or late-transition metals (Fe, Co and Ni). The effect of positioning two polymerization-active metal centers in close proximity on catalytic activity, molecular weight, molecular weight distribution and levels of branching are thoroughly documented. Compartmental ligands comprising binding domains consisting of phenoxyimines, ansa-bridged cyclopentadienyl-amides, α-diimines and iminopyridines are described as is their capacity to serve as compatible binucleating supports for homobimetallic and also for the less investigated heterobimetallic counterparts. By comparison with their mononuclear analogues, any synergic properties exhibited by these binuclear catalysts represents an underlying theme to be developed where possible throughout this review

Recent advances in Ni-mediated ethylene chain growth: Nimine-donor ligand effects on catalytic activity, thermal stability and oligo-/polymer structure

Homogeneous nickel catalysts have a considerable track record for mediating ethylene chain growth in the form of oligomerization and more recently polymerization. Within the polymerization arena, high molecular weight materials incorporating various degrees of branching, anywhere from linear to moderately branched through to hyperbranched, highlight the versatility of this type of catalyst. This review focuses on recent progress related to structural modifications made to the pre-catalyst, and in particular to the multidentate Nimine-ligand manifold, and how these changes impact on thermal stability and activity of the catalyst as well as the microstructural properties of the polyethylene and the distribution of the oligomeric fractions. In addition to ongoing process development directed towards commodity-type polyolefinic materials, the emergence of nickel catalysts that can form elastomeric-type materials from a single ethylene feed, without the addition of a high-cost α-olefin such as 1-hexene or 1-octene, offers considerable opportunities for future commercial applications

Correction: Resonance Raman spectroscopy as an in situ probe for monitoring catalytic events in a Ru-porphyrin mediated amination reaction

Correction for ‘Resonance Raman spectroscopy as an in situ probe for monitoring catalytic events in a Ru-porphyrin mediated amination reaction’ by Paolo Zardi et al., Analyst, 2016, 141, 3050–3058

Carbocyclic-fused N,N,N-pincer ligands as ring-strain adjustable supports for iron and cobalt catalysts in ethylene oligo-/polymerization

Recent progress in the application of homogeneous iron and cobalt catalysts in ethylene oligo-/polymerization is reviewed with particular emphasis placed on the tuning of catalyst performance through the introduction of controlled amounts of ring strain to the ligand frame. While new examples of catalysts bearing the prototypical bis(arylimino)pyridine continue to emerge in the literature, the last decade has witnessed a number of key advances concerned with the fusion of carbocyclic units to the N,N,N-pincer manifold with a view to enhancing both the catalytic activities and thermal stablility of their resultant catalysts. Some notable examples include iron complexes containing aryl-fused imino-phenanthroline ligands, which have proved highly active catalysts for ethylene oligomerization and indeed have shown considerable industrial promise on the pilot plant scale. Elsewhere, bis(arylimino)pyridines incorporating singly or doubly fused cycloalkyl units with the ring sizes anywhere between five- and eight-membered have been systematically developed and have proved versatile supports for both metal centers. More significantly, clear correlations between structure and activity as well as oligo-/polymer properties are a feature of these strain-adjustable catalysts. In many cases, linear vinyl-polyethylenes are accessible which are in demand for the production of long-chain branched copolymers, functional polymers as well as coating materials