Facile synthesis of sterically demanding SHOP‐type nickel catalysts for ethylene polymerization

The P,O‐chelated shell higher olefin process (SHOP) type nickel complexes are practical homogeneous catalysts for the industrial preparation of linear low‐carbon α‐olefins from ethylene. We describes that a facile synthetic route enables the modulation of steric hindrance and electronic nature of SHOP‐type nickel complexes. A series of sterically bulky SHOP‐type nickel complexes with variable electronic nature, {[4‐R‐C₆H₄C(O) = C‐PArPh]NiPh (PPh₃); Ar = 2‐[2′,6′‐(OMe)₂C₆H₃]C₆H₄; R = H ( Ni1 ); R = OMe ( Ni2 ); R = CF₃ ( Ni3 )}, were prepared and used as single component catalysts toward ethylene polymerization without using any phosphine scavenger. These nickel catalysts exhibit high thermal stability during ethylene polymerization and result in highly crystalline linear α‐olefinic solid polymer. The catalytic performance of the SHOP‐type nickel complexes was significantly improved by introducing a bulky ortho‐biphenyl group on the phosphorous atom or an electron‐withdrawing trifluoromethyl on the backbone of the ligand, indicating steric and electronic effects play critical roles in SHOP‐type nickel complexes catalyzed ethylene polymerization.     

η3-Allylnickel alkoxides and their use as homogeneous and heterogeneous catalysts for the dimerization of olefins

η³-Allylnickel alkoxides {η³-C₃H₅NiOR}₂ (R = Me, Et, i-Pr, Ph, SiPh₃) may be activated by gaseous boron trifluoride (BF₃) to give active catalysts for the dimerization of propene in homogeneous phase. In CH₂Cl₂ at ?20 °C catalytic turnover numbers of 5000 mol propene(mol Ni)^?1h^?1 were measured. The nature of the OR group influences both the catalytic activity and the oligomerization product distribution. The ratio of methylpentenes to dimethylbutenes in the dimer fraction may be controlled by the presence of additional phosphine ligands at the nickel atom. The nickel alkoxide precursor was heterogenized on alumina to give {Al₂O₃}–O–Ni–(η³-C₃H₅). Subsequent activation using gaseous BF₃ generates a powerful heterogeneous olefin dimerization catalyst which converts 50 × 10³ mol propene (mol Ni)^?1 at ?10° to ?5°C in a batchwise process and 143 × 10³ mol propene (mol Ni)^?1 continuously to give 75% dimers and 25% higher oligomers. The solvent-free treatment of oxide supports, e.g. alumina or silica, with gaseous BF₃ produces strong ‘solid acids’. The activated hydroxyl groups on the support surface serve as effective anchor sites for organometallic complexes to form heterogenous catalysts. By reaction of Ni(cod)₂ with {Al₂O₃}O(BF₃)H or {SiO₂}O(BF₃)H, η¹, η²-cyclo-octenylnickel–O fragments may be fixed to the surface. In the absence of halogenated solvents, the resulting catalysts, e.g. {SiO₂}O–(BF₃)–Ni–(η¹, η²-C₈H₁₃), dimerize propene continuously at +5°C at the rate of 800 × 10³ mol liquid propene (mol Ni)^?1.     

Indolyl Phosphine Nickel(II) Fluorido Complexes: Synthesis and Intermediates in Suzuki–Miyaura Cross-Coupling Reactions

The C−F bond activation of pentafluoropyridine and 2,3,5,6-tetrafluoropyridine at [Ni(cod)₂] (cod=1,5-cyclooctadiene) in the presence of the phosphine PPh₂(Ind) (Ind=3-methyl-2-indolyl) led to the formation of the nickel(II) fluorido bis(phosphine) complexes trans-[Ni(F)(2-C₅NF₄){PPh₂(Ind)}₂] and trans-[Ni(F)(2-C₅HNF₃){PPh₂(Ind)}₂]. The complexes are characterized by the presence of intramolecular hydrogen bonds between the NH group of the phosphine ligands and the fluorido ligand. Stochiometric model reactions of nickel(II) fluorido complexes with PhB(OH)₂ revealed that the former can be considered as intermediates in Suzuki–Miyaura cross coupling reactions. Catalytic experiments were attempted using 10 mol-% of trans-[Ni(F)(2-C₅NF₄){PPh₂(Ind)}₂] as catalyst and the activities of the PPh₂(Ind) complex were compared to the ones of an analogous nickel(II) fluorido complex, bearing PPh₃ instead of PPh₂(Ind) as ligands. The latter exhibited a somewhat lower catalytic activity suggesting a slight influence of the H-bonds in the outer coordination sphere.     

Electrocatalytic oxidation of formate by [Ni(P(R)2N(R')2)2(CH3CN)]2+ complexes

[Ni(P(R)(2)N(R')(2))(2)(CH(3)CN)](2+) complexes with R = Ph, R' = 4-MeOPh or R = Cy, R' = Ph , and a mixed-ligand [Ni(P(R)(2)N(R')(2))(P(R'(2))N(R'(2)))(CH(3)CN)](2+) with R = Cy, R' = Ph, R' = Ph, have been synthesized and characterized by single-crystal X-ray crystallography. These and previously reported complexes are shown to be electrocatalysts for the oxidation of formate in solution to produce CO(2), protons, and electrons, with rates that are first-order in catalyst and formate at formate concentrations below ～0.04 M (34 equiv). At concentrations above ～0.06 M formate (52 equiv), catalytic rates become nearly independent of formate concentration. For the catalysts studied, maximum observed turnover frequencies vary from <1.1 to 15.8 s(-1) at room temperature, which are the highest rates yet reported for formate oxidation by homogeneous catalysts. These catalysts are the only base-metal electrocatalysts as well as the only homogeneous electrocatalysts reported to date for the oxidation of formate. An acetate complex demonstrating an η(1)-OC(O)CH(3) binding mode to nickel has also been synthesized and characterized by single-crystal X-ray crystallography. Based on this structure and the electrochemical and spectroscopic data, a mechanistic scheme for electrocatalytic formate oxidation is proposed which involves formate binding followed by a rate-limiting proton and two-electron transfer step accompanied by CO(2) liberation. The pendant amines have been demonstrated to be essential for electrocatalysis, as no activity toward formate oxidation was observed for the similar [Ni(depe)(2)](2+) (depe = 1,2-bis(diethylphosphino)ethane) complex.     

Alkane Oxidation by an Immobilized Nickel Complex Catalyst: Structural and Reactivity Differences Induced by Surface‐Ligand Density on Mesoporous Silica

Immobilized nickel catalysts SBA*‐ L ‐x/Ni ( L =bis(2‐pyridylmethyl)(1H‐1,2,3‐triazol‐4‐ylmethyl)amine) with various ligand densities ( L content (x)=0.5, 1, 2, 4 mol % Si) have been prepared from azidopropyl‐functionalized mesoporous silicas SBA‐N₃‐x. Related homogeneous ligand LtBu and its Ni^II complexes, [Ni( LtBu )(OAc)₂(H₂O)] ( LtBu /Ni) and [Ni( LtBu )₂]BF₄ (2 LtBu /Ni), have been synthesized. The L /Ni ratio (0.9–1.7:1) in SBA*‐ L ‐x/Ni suggests the formation of an inert [Ni L ₂] site on the surface at higher ligand loadings. SBA*‐ L ‐x/Ni has been applied to the catalytic oxidation of cyclohexane with m‐chloroperbenzoic acid (mCPBA). The catalyst with the lowest loading shows high activity in its initial use as the homogeneous LtBu /Ni catalyst, with some metal leaching. As the ligand loading increases, the activity and Ni leaching are suppressed. The importance of site‐density control for the development of immobilized catalysts has been demonstrated.     

Development in the green synthesis of cyclic carbonate from carbon dioxide using ionic liquids

This brief review presents the recent development in the synthesis of cyclic carbonate from carbon dioxide (CO₂) using ionic liquids as catalyst and/or reaction medium. The synthesis of cyclic carbonate includes three aspects: catalytic reaction of CO₂ and epoxide, electrochemical reaction of CO₂ and epoxide, and oxidative carboxylation of olefin. Some ionic liquids are suitable catalysts and/or solvents to the CO₂ fixation to produce cyclic carbonate. The activity of ionic liquid is greatly enhanced by the addition of Lewis acidic compounds of metal halides or metal complexes that have no or low activity by themselves. Using ionic liquids for the electrochemical synthesis of the cyclic carbonate can avoid harmful organic solvents, supporting electrolytes and catalysts, which are necessary for conventional electrochemical reaction systems. Although the ionic liquid is better for the oxidative carboxylation of olefin than the ordinary catalysts reported previously, this reaction system is at a preliminary stage. Using the ionic liquids, the synthesis process will become greener and simpler because of easy product separation and catalyst recycling and unnecessary use of volatile and harmful organic solvents.     

Synthesis and spectral studies on NiS<Subscript>4</Subscript>, NiS<Subscript>2</Subscript>PN,NiS<Subscript>2</Subscript>P<Subscript>2</Subscript> chromophores: Single-crystal X-ray structure of [Ni(dbpdtc)<Subscript>2</Subscript>] (dbpdtc = benzyl(4-(benzylamino)phenyl)dithiocarbamate)

Three complexes of a dithiocarbamate ligand (dbpdtc = benzyl(4-(benzylamino)phenyl)dithiocarbamate), namely [Ni(dbpdtc)₂] (1), [Ni(dbpdtc)(NCS)(PPh₃)] (2) and [Ni(dbpdtc)(PPh₃)₂]ClO₄ (3) have been prepared. The complexes were characterized by IR, electronic spectroscopy and cyclic voltammetry. A single-crystal X-ray structural analysis was carried out for complex 1 and showed that the nickel is in a distorted square planar environment with a NiS₄ chromophore. For the two mixed ligand complexes, the thioureide ν _C–N values were shifted to higher wavenumbers compared to [Ni(dbpdtc)₂], suggesting increased strength of the thioureide bond due to the presence of the π-accepting phosphine. Electronic spectral studies suggest square planar geometries for the complexes. Cyclic voltammetry showed easier reduction of nickel(II) to nickel(I) in the mixed ligand complexes compared to [Ni(dbpdtc)₂].     

New dinuclear nickel(II) complexes: synthesis, structure, electrochemical, and magnetic properties

The reaction of [NiBr(2)(bpy)(2)] (bpy = 2,2'-bipyridine) with organic phosphinic acids ArP(O)(OH)H [Ar = Ph, 2,4,6-trimethylphenyl (Mes), 9-anthryl (Ant)] leads to the formation of binuclear nickel(II) complexes with bridging ArP(H)O(2)(-) ligands. Crystal structures of the binuclear complexes [Ni(2)(μ-O(2)P(H)Ar)(2)(bpy)(4)]Br(2) (Ar = Ph, Mes, Ant) have been determined. In each structure, the metal ions have distorted octahedral coordination and are doubly bridged by two arylphosphinato ligands. Magnetic susceptibility measurements have shown that these complexes display strong antiferromagnetic coupling between the two nickel atoms at low temperatures, apparently similar to binuclear nickel(II) complexes with bridging carboxylato ligands. Cyclic voltammetry and in situ EPR spectroelectrochemistry show that these complexes can be electrochemically reduced and oxidized with the formation of Ni(I),Ni(0)/Ni(III) derivatives.     

Synthesis,Spectral, Cyclic Voltammetric Studies,and Single Crystal X‐Ray Structure Determination of the Planar NiS2P2, NiS2PN,and NiS2PC Chromophores

Synthesis, spectral and cyclic voltammetric characterization of [Ni(dedtc)(4‐MP)₂](ClO₄) ( 1 ), [Ni(dedtc)(4‐MP)(NCS)]( 2 ), [Ni(dedtc)(PPh₃)(NCS)] ( 3 ) and [Ni(dedtc)(PPh₃)(CN)] ( 4 ) (dedtc = diethyldithiocarbamate, 4‐MP = tri(4‐methylphenyl)phosphine, PPh₃ = triphenylphophine) are reported. IR spectra of complexes 1‐4 show the characteristic thioureide (C‐N) bands at higher wave numbers compared to that of the parent dithiocarbamate complex [Ni(dedtc)₂]. The d‐d transitions are observed in the region 452—482 nm. The CV studies clearly show the presence of reduced electron density on the nickel ions in mixed ligand complexes 1‐4 compared to the parent dithiocarbamate. Single crystal X‐ray structure studies show all the complexes to containplanar NiS₂P₂, NiS₂PN, and NiS₂PC chromophores in keeping with the observed diamagnetism. In all the complexes the Ni‐S distances are asymmetric. The thioureide C‐N distance of the complexes 1‐4 are less thanthe C‐N distance observed in the parent [Ni(dedtc)₂].     

Silicon hydrides and nickel complexes : II. Mechanism of the hydrosilylation catalyzed by nickel-phosphine complexes

Two ethylene-nickel(0) complexes, viz., [1,2-bis(diphenylphosphino)ethane]-(ethylene)nickel(0) and bis(triphenylphosphine)(ethylene)nickel(0) have been used in a comparison of their catalytic activities in hydrosilylation reactions with those of the corresponding nickel(II) complexes, viz., dichloro [1,2-bis(diphenylphosphino)-ethane]nickel(II) and dichlorobis(triphenylphosphine)nickel(II). The reaction profiles are similar, apart from a significant difference in the induction period; the nickel(II) catalysts requiring a substantially longer time. A mechanism involving a nickel(0) species is proposed for the hydrosilylation.The interchange of hydrogen and chlorine on silicon accompanying the hydrosilylation is related to a high electron density at the nickel atom bearing the phosphine, olefin, and silicon hydride ligands.     

Co-oligomerization of ethylene and higher linear alpha olefins. II. Olefin reactivities in various reaction steps of co-oligomerization with nickel ylide-based system

Part I described co-oligomerization reactions of ethylene and various linear α-olefins (propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, and 1-decene) in the presence of the homogeneous catalyst consisting of sulfonated nickel ylide and diethylaluminum ethoxide. The present article analyzes olefin reactivities in various reaction steps of the co-oligomerization reactions as well as reactivities of various catalytic species. Chain propagation reactions (insertion into the Ni? C bonds) with participation of α-olefins exhibit poor regioselectivity, primary insertion being ca. 60% more probable than the secondary insertion. Ethylene is significantly more reactive in chain propagation reactions: 50–70 times compared to olefin primary insertion and 100–120 times compared to olefin secondary insertion. Reactivities of α-olefins in chain propagation reactions decrease slightly for higher olefin alkyl groups. Reactivities of Ni? C bonds in chain propagation and chain termination reactions strongly depend on the structure of the alkyl group attached to the nickel atom. The Ni? CHR? CH₂? R bond has very low reactivity in ethylene insertion reaction and usually decomposes in the α-hydrogen elimination process. Kinetic analysis of olefin co-oligomerization reactions provides numerous analogies with olefin copolymerization reactions in the presence of Ziegler–Natta catalysts.     

Synthesis and structures of nickel and palladium salicylaldiminato 1,3,5-triaza-7-phosphaadamantane (PTA) complexes

The synthesis of nickel(II) and palladium(II) salicylaldiminato complexes incorporating the water-soluble phosphine 1,3,5-triaza-7-phosphaadamantane(PTA) has been achieved employing two preparative routes. Reaction of the original ethylene polymerization catalyst developed by Grubbs and co-workers (Organometallics 1998, 17, 3149), (salicylaldiminato)Ni(Ph)PPh(3), with PTA using a homogeneous methanol/toluene solvent system resulted in the formation of the PTA analogues in good yields. Alternatively, complexes of this type may be synthesized via a direct approach utilizing (tmeda)M(CH(3))(2) (M = Ni, Pd), the corresponding salicylaldimine, and PTA. Yields by this method were generally near quantitative. The complexes were characterized in solution by (1)H/(13)C/(31)P NMR spectroscopy and in the solid-state by X-ray crystallography. All derivatives exhibited square-planar geometry with the bulky isopropyl groups on the aniline being perpendicular to the plane formed by the metal center and its four ligands. Such orientation of these sterically encumbering groups is responsible for polymer chain growth during olefin polymerization in favor of chain termination via beta-hydride elimination. Polymerization reactions were attempted using the nickel-PTA complexes in a biphasic toluene/water mixture in an effort to initiate ethylene polymerization by trapping the dissociated phosphine ligand in the water layer, thereby eliminating the need for a phosphine scavenger. Unfortunately, because of the strong binding ability of the small, donating phosphine(PTA) as compared to PPh(3), phosphine dissociation did not occur at a temperature where the complexes are thermally stable.     

Coordination complexes of acetylenic phosphines and diphosphines

The reactions of π-cyclopentadienylnickel carbonyl dimer with 3,3,3-trimethylpropynyldiphenylphosphine and phenylethynyldiphenylphosphine are described. The products have been characterized by elemental and mass spectral analysis, infrared and NMR spectroscopy. An acetylene bridged complex (π-C₅H₅Ni)₂Ph₂PC₂-t-Bu, containing an uncoordinated phosphorus atom, has been prepared. The complex can be oxidized to the phosphine oxide derivative (π-C₅H₅Ni)₂Ph₂P(O)C₂-t-Bu and converted to the phosphonium salts with methyl iodide or ethyl bromide. These are the first reported π-complexes of phosphonium salts. The complex (π-C₅H₅Ni)₂Ph₂PC₂-t-Bu forms the novel mixed metal derivative [PdCl₂][(π-C₅H₅Ni)₂Ph₂PC₂-t-Bu]₂ from bis(benzonitrile)-palladium dichloride. The dicarbonyl complexes Ni(CO)₂(Ph₂PC₂R)₂ (R  t-Bu, Ph), the phosphine oxide complex (π-C₅H₅Ni)₂(Ph₂P(O)C₂Ph) and the trinuclear nickel carbonyl derivative Ni(CO)₃[(π-C₅H₅Ni)₂Ph₂PC₂Ph] are described.     

Electroanalytical investigation on the stability of tetracoordinate nickel(I) complexes

The stability of tetracoordinate nickel(I) complexes, of the type [Ni(CN)₂P₂]^? (P=substituted phosphine), generated by cathodic reduction of the parent nickel(II) complexes, has been studied by cyclic voltammetry and double potential step techniques. Evidence has been obtained that nickel(I) complexes decay to the dimeric species Ni₂(CN)₂P₄ via a first order chemical reaction the rate determining step being the release of a cyanide ion leading to the radical species [Ni(CN)P₂]. The experimental trend obtained for the first order kinetic constants has been explained on the basis of the different “trans-effect” induced by a cyanide ligand in comparison with that induced by a phosphine group and taking into account the different basic character of the phosphine ligands.     

Study of Palladium Complexes with Chitosan and Its Derivatives as Potential Catalysts for Terminal Olefin Oxidation

FTIR spectroscopy and XPS are used to study palladium complexes with various forms of chitosan: initial and modified by glutaric aldehyde. IR bands are identified that are related to the Pd–N and Pd–O bonds. A difference between the spectra of complexes obtained by the methods of adsorption and coprecipitation of chitosanium hydrochloride with the tetrachloropalladate ion is found. It is shown that the systems studied can be used as catalysts for terminal olefin oxidation by oxygen in the presence of H₂O₂. In the course of the reaction, the complexes undergo redox transformations without breaking the structure of the complex or metal transfer to the reaction mixture. The use of heterogenized Pd(II) complexes as catalysts in terminal olefin oxidation leads to the formation of oxidation and isomerization products, similarly to the case of homogeneous oxidation.     

Polymerization of styrene by Novel Ni(a)‐ and Pd(II)‐based complexes

The catalytic activities of nine neutral nickel and palladium α‐acetylide complexes [M= (C=CR)₂(PR'₃)₂, M=Ni, Pd; R = Ph, CH₂OH, CH₂OOCH, CH₂OOCPh, CH₂OOCPhOH‐o; R' = Ph, Bu] are compared. Among them, Ni(C‐CPh)₂(PBu₃)] shows the highest catalytic activity and gives the polystyrene with high molecular weight (M_w= 188800) and a syndio‐rich microstructure. The catalytic behavior of transition metal acetylides is related to metal, phosphine, and alkynyl ligands bonded to the metal atoms.     

Structural characterization and preliminary decomposition study of four unsymmetrically substituted nickel dithiocarbamate complexes

Single-crystal X-ray structures of four nickel dithiocarbamate complexes, the homoleptic mixed-organic bis-dithiocarbamates Ni[S₂CN(isopropyl)(benzyl)]₂, Ni[S₂CN(ethyl)(n-butyl)]₂, and Ni[S₂CN(phenyl)(benzyl)]₂, as well as the heteroleptic mixed-ligand complex NiCl[P(phenyl)₃][(S₂CN(phenyl)(benzyl)], were determined. A slightly distorted square-planar nickel coordination environment was observed for all four complexes. The organic residues adopt conformations to minimize steric interactions. Steric effects also may determine puckering, if any, about the nickel and nitrogen atoms, both of which are planar or nearly so. A trans-influence affects the Ni-S bond distances. Nitrogens interact with the CS₂ carbons with a bond order near two; the other substituents on nitrogen display transoid conformations. There are no strong intermolecular interactions, consistent with prior observations of the volatility of nickel dithiocarbamate complexes. A preliminary thermolysis study of the homoleptic species results in production of 1?:?1 nickel sulfide phases, indicating the potential utility of these species as “single-source” precursors.     

Synthesis,characterization and biological activity studies of octahedral nickel(II) complexes

Abstract  

Three nickel(II) complexes, namely [Ni(BH)₃](H₂O)(NO₃)(ClO₄) 1, [Ni(BH)₂(NO₃)₂] 2 and [Ni(BH)(Tren)](ClO₄)₂ 3 (BH = Benzoylhydrazine, Tren = Tris(2-aminoethyl)amine) have been synthesized and characterized by physico-chemical techniques. X-ray crystallographic analysis shows the nickel to be six-coordinated in these complexes. The complexes are efficient catalysts for the dismutation of superoxide in alkaline DMSO-NBT assays. The IC₅₀ values are 74,108 and 105 μM for 1, 2 and 3, respectively.     

The Importance of Ligand-Induced Backdonation in the Stabilization of Square Planar d10 Nickel π-Complexes

The electronic nature of Ni π-complexes is underexplored even though these complexes have been widely postulated as intermediates in organometallic chemistry. Herein, the geometric and electronic structure of a series of nickel π-complexes, Ni(dtbpe)(X) (dtbpe=1,2-bis(di-tert-butyl)phosphinoethane; X=alkene or carbonyl containing π-ligands), is probed using a combination of ³¹P NMR, Ni K-edge XAS, Ni K_β XES, and DFT calculations. These complexes are best described as square planar d¹⁰ complexes with π-backbonding acting as the dominant contributor to M−L bonding to the π-ligand. The degree of backbonding correlates with ²J_PP from NMR and the energy of the Ni 1s→4p_z pre-edge in the Ni K-edge XAS data, and is determined by the energy of the π*_ip ligand acceptor orbital. Thus, unactivated olefinic ligands tend to be poor π-acids whereas ketones, aldehydes, and esters allow for greater backbonding. However, backbonding is still significant even in cases in which metal contributions are minor. In such cases, backbonding is dominated by charge donation from the diphosphine, which allows for strong backdonation, although the metal centre retains a formal d¹⁰ electronic configuration. This ligand-induced backbonding can be formally described as a 3-centre-4-electron (3c-4e) interaction, in which the nickel centre mediates charge transfer from the phosphine σ-donors to the π*_ip ligand acceptor orbital. The implications of this bonding motif are described with respect to both structure and reactivity.     

Synthesis and activity of ruthenium alkylidene complexes coordinated with phosphine and N-heterocyclic carbene ligands

This paper reports the synthesis and characterization of a variety of ruthenium complexes coordinated with phosphine and N-heterocyclic carbene (NHC) ligands. These complexes include several alkylidene derivatives of the general formula (NHC)(PR(3))(Cl)(2)Ru=CHR', which are highly active olefin metathesis catalysts. Although these catalysts can be prepared adequately by the reaction of bis(phosphine) ruthenium alkylidene precursors with free NHCs, we have developed an alternative route that employs NHC-alcohol or -chloroform adducts as "protected" forms of the NHC ligands. This route is advantageous because NHC adducts are easier to handle than their free carbene counterparts. We also demonstrate that sterically bulky bis(NHC) complexes can be made by reaction of the pyridine-coordinated precursor (NHC)(py)(2)(Cl)(2)Ru=CHPh with free NHCs or NHC adducts. Two crystal structures are presented, one of the mixed bis(NHC) derivative (H(2)IMes)(IMes)(Cl)(2)Ru=CHPh, and the other of (PCy(3))(Cl)(CO)Ru[eta(2)-(CH(2)-C(6)H(2)Me(2))(N(2)C(3)H(4))(C(6)H(2)Me(3))], the product of ortho methyl C-H bond activation. Other side reactions encountered during the synthesis of new ruthenium alkylidene complexes include the formation of hydrido-carbonyl-chloride derivatives in the presence of primary alcohols and the deprotonation of ruthenium vinylcarbene ligands by KOBu(t). We also evaluate the olefin metathesis activity of NHC-coordinated complexes in representative RCM and ROMP reactions.