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The reaction of [Ni5(CO)12]2- or [Ni 6(CO)12]2- with GaCl3 in dichloromethane under a nitrogen atmosphere affords a mixture of [Ni 12+x(μ12-Ga)(CO)22+x]3- (x = 0-3) clusters. Short exposure of the above mixture to a carbon monoxide atmosphere leads to the green icosahedral [Ni12(μ12-Ga)(CO) 22]3- trianion, which was isolated and characterized as its [NnBu4]+ salt. In contrast, crystallization of the above mixture in the presence of Ni(CO)4 enabled isolation of a cocrystallized mixture of [Ni14(μ12-Ga)(CO) 24]3- (70%) and [Ni15(μ12-Ga)(CO) 25]3- (30%). As inferable from its structure, the additional three Ni(CO) moieties condense onto interlayer faces of the icosahedron. Protonation of [Ni12(μ12-Ga)-(CO) 22]3- affords the corresponding [HNi12(μ 12-Ga)(CO)22]2- hydride derivative, which was isolated in a pure state and fully characterized. All of the above compounds conform to the cluster-borane analogy, by the inclusion principle, and none exhibits relevant redox behaviour.

Reaction of NiCl2 in THF with 2 equiv of Li(CPh3) at -25 °C results in formation of Ni(η3-CPh3)2 (1) in moderate yield. Complex 1 was fully characterized, which included analysis by X-ray crystallography. In the solid state, 1 features an η3 binding mode

The reaction of [Ni10(C2) (CO)16]2- with CuCl in thf affords [Ni45C10(CO)46]6- as the major product. This represents the first deca-carbide carbonyl cluster and this i

The reaction of [Ni9C(CO)17]2- with CdX2 · xH2O (X = Cl, Br, I) affords the tetra-carbide carbonyl clusters [H6-nNi30C4(CO)34(CdX)2]n-

The reaction of [Ni8C(CO)I7]2- (1) with [Rh(cod)Cl]2 (2) results in the formation of the new hetero-bimetallic [Ni10Rh2C(CO)20]2 (3) and [Ni9Rh3C

The flame combustion synthesis of Cu/ZnO/Al2O3 catalysts for the synthesis of methanol from CO, CO2, and H2 was studied. A low peak temperature and quench cooling of the flame tended to increase the dispersion of the phases and the specific surface area of the particles. The specific surface area varied from ≤ 100 sq m/g for samples without aluminum to several hundred square m per gram for the respective compositions of pure Al2O3 and ZnAl2O4. The samples prepared and tested with copper as one of the components showed potential for use as methanol catalysts. The contribution of ZnAl2O4 to an increased surface area and thermal stability was the explanation of the beneficial role of alumina in the methanol synthesis catalyst. Although Cu/Al2O3 showed methanol synthesis activity, the Cu-based turnover frequency was inferior to that of the ZnO-containing catalysts. Methane, which is the only detectable by-product of the reaction, was produced in minute amounts unless the catalyst was contaminated by nickel.

N-heterocyclic carbene ligands IMes (1), SIMes (2), IPr (3), SIPr (4), and ICy (5) react with Ni(CO)4 to give the saturated tricarbonyl complexes Ni(CO)3(IMeS) (8), Ni(CO)3(SIMeS) (9), Ni(CO)3(IPr) (10), Ni(CO)3(SIPr) (11), and Ni(CO) 3(ICy) (12), respectively. The electronic properties of these complexes have been compared to their phosphine analogues of general formula Ni(CO)3(PR3) by recording their vco stretching frequencies. While all of these NHCs are better donors than tertiary phosphines, the differences in donor properties between ligands 1-5 are surprisingly small. Novel, unsaturated Ni(CO)2(IAd) (13) and Ni(CO)2(I tBu) (14) compounds are obtained from the reaction of Ni(CO) 4 with IAd (6) and ItBu (7). Complexes 13 and 14 are highly active toward substitution of the NHC as well as the carbonyl ligands. This has allowed the determination of Ni-C(NHC) bond dissociation energies and the synthesis of various unsaturated Ni(0) and Ni(II) complexes. Computational studies on compounds 8-14 are in line with the experimental findings and show that IAd (6) and ItBu (7) are more bulky than IMes (1), SIMes (2), IPr (3), SIPr (4), and ICy (5). Furthermore, a method based on % Vbur values has been developed for the direct comparison of steric requirements of NHCs and tertiary phosphines. Complexes 8-14, as well as NiCl(C 3H5)(ItBu) (16) and NiBr(C3H 5)(ItBu) (17), have been characterized by X-ray crystallography.

The kinetics of the formation of a paramagnetic nickel(I) complex from bis(η3-allyl)nickel under conditions of catalytic norbornadiene dimerization is reported. It is demonstrated by ESR and GLC that the concentrations of Ni(I), norbornadiene and its pentacyclic dimers change in the same way. It might be inferred from this finding that Ni(I) is involved in the catalytic process as an intermediate. However, experiments on model systems have not confirmed this assumption. At the same time, they have not ruled out the participation of the paramagnetic complex in side catalytic reactions. The presence of Ni(I) in the reaction system is connected with the presence of free norbornadiene there. Hypotheses as to the probable structure and formation mechanism of the paramagnetic Ni(I) are suggested.

Amazing the crowd: A highly dispersive supported nickel catalyst is prepared by in situ decomposition of Ni(CO)4 over ZSM-5 zeolite. The catalyst displays an amazing activity for complete hydrogenation of polymethylbenzenes which are extremely

Reaction of [Ni6(CO)12]2- in thf with 2 equiv. of the soft Lewis acid CdCl2·2.5H2O gives the new dimeric species {Cd2Cl3[Ni6(CO) 12]2}3-/su

The reaction of [N(PPh3)2]2[Ni6(CO)12] with Cu(PPh3)xCl (x=1, 2), as well as the degradation of [N(PPh3)2]2[H2Ni12 (CO)21] with PPh3, affords the new and unstable dark orange-brown [N(PPh3)2]2[Ni9(CO) 16].THF salt in low yields. This salt has been characterized by a CCD X-ray diffraction determination, along with IR spectroscopy and elemental analysis. The close-packed two-layer metal core geometry of the [Ni9(CO)16]2- dianion is directly related to that of the bimetallic [Ni6Rh3(CO)17]3- trianion and may be envisioned to be formally derived from the hcp three-layer geometry of [Ni12(CO)21]4- by the substitution of one of the two outer [Ni3(CO)3(μ-CO)3]2- layers with a face-bridging carbonyl group.

There has always been extra focus on the bonding characteristics of monocarbonyls since they are deemed as the models of the CO binding to the metal surface. Laser-ablated Ni, Pd, and Pt atoms were reacted with CO molecules during condensation in a neon matrix at 4 K. Annealing, photolysis, and isotopic substitution experiments identified metal carbonyl anions [M(CO)n- (n = 1-3)] and cations [Ni(CO)n+ (n = 1-4); Pd(CO)n+ (n = 1,2); Pt(CO)n+ (n = 1-3)], and neutrals [M(CO)n (n = 1-4)]. Doping with the CCl4 electron trap increased cation and decreased anion absorptions and supported the identification of the ionic species. The density functional theory (DFT) calculations showed that experimental results agreed excellently with frequencies and isotopic frequency ratios, confirming the vibrational assignments and the identification of these metal carbonyl complexes. All the monocarbonyls were linear, except PdCO- and PtCO-, which were computed to be bent by both DFT/B3LYP and BP86 functionals. Natural bonding orbital analysis on the monocarbonyls, conducted to describe the bonding of CO to transition metals, showed that: C-O bond orders were cations > neutrals > anions, indicating that C-O stretching frequencies have the same order as seen for other transition metals; and the various configurations of metal atoms in anions, cations, or neutrals could be employed to explain the different geometries.

All four carbonyls of nickel, Ni(CO)1-4, and possibly six carbonyls of tantalum, Ta(CO)1-6, have been identified via infrared spectra in argon matrices at 4.2°K. The carbonyls are prepared by the vaporization of the metal atoms and condensation into a CO-argon mixture. C18O was also used in the identification. Careful warming of the matrix results in the growth and disappearance of νco bands in the 2000-cm-1 region. In the nickel experiments these bands appear at 2052, 2017, 1967, and 1996 cm-1 and are assigned to Ni(CO)4, Ni(CO)3, Ni(CO)2, and NiCO, respectively. Specific assignments for tantalum carbonyls are more difficult, but five or six molecules are definitely formed during the diffusion experiments. For the tantalum carbonyls also, the general trend is that the stretching frequencies increase with increasing coordination number, a fact which is predicted on the basis of simple bonding theory. In the electronic spectra broad absorptions at 3000 and 2725 A? are attributed to Ni(CO)4 and Ta(CO)6, respectively.

Reaction of with 2- results in a complicated mixture of mixed Co-Ni carbide carbonyl clusters, among which the 3- trianion has been isolated in a pure crystalline state and fully characterized by X-ray crystallography.The metal framework of this compound is unprecedented in cluster geometries and may be described as a square antiprism of metal atoms tetra-capped on two alternate pairs of adjacent triangular faces.Despite the presence of a caged carbon atom in the square-antiprismatic cavity, the compound is readily degraded by carbon monoxide (25 deg C, 1 atm) mainly to a mixture of - and .Corresponding degradation of the cluster under a mixture of carbon monoxide and hydrogen yields, in addition, trace amounts of organics, mainly C1 and C2 hydrocarbons, probably derived from the carbide atom.

Nickel CVT, based on the following chemical equilibrium: Ni(s) + 4CO(g) Ni(CO)4(g), has been studied by Raman spectroscopy.The temperature of the gaseous mixture can be calculated from the experimental intensities of CO rotational Raman-Stokes lines.The simulation of CO spectrum has been made from the theoretical intensities of lines convoluted with functions taking account of the incident band shape (Gaussian function) and slit geometry (apparatus function).Simulated and experimental spectra are in a good agreement and the calculated temperature is found with a precision of one Celsius degree compared with the temperature at 1/10 deg C precisely.From the Ni(CO)4 vibration VS(Al) at 370.6 cm-1 available both in Stokes and anti-Stokes fields, we have another method of temperature calculation (SAS method).At a known temperature, the same vibration can be used to compute the partial pressure of Ni(CO)4.Results obtained are compared with those directly measured with a tensimeter.The temperature and the pressure respectively determined from the CO rotation lines and the Ni-C symmetric streching vibration at 370.6 cm- permit us to follow the nickel CVT in a transparent furnace (SnO2 technology).

The reactions of Ni(cod)2 (cod = 1,5-cyclooctadiene), Ni(cdt) (cdt = trans,trans,trans-1,5,9-cyclododecatriene), and Ni(C2H4)3 with N,N,N',N'-tetramethylethylenediamine (tmeda) and tetrafluoroethene in ether yield almost quantitatively yellow needles of (

(tmeda)Ni(acac)2 reacts with the main group metal compounds (tmeda)Mg(CH3)2, (tmeda)2, and (C2H5O)Al(CH3)2 at 0 deg C to give (tmeda)Ni(CH3)2 (1), which can be isolated as fine yellow crystals in 50-80 percent yield.Complex 1, which is the simplest dialkyl nickel(II) compound with a hard donor ligand, is suprisingly stable and decomposes only at 79 deg C. 1 is converted by bipy to (bipy)Ni(CH3)2 and by Me2PC2H4PMe2 to (Me2PC2H4PMe2)Ni(CH3)2.Upon reaction of 1 with strong ?-acceptor molecules (acrylic acid methylester, methyl vinyl ketone, acrylonitrile, tetracyanoethene, tetrafluoroethene, maleic anyhdride) reductive elimination of the methyl groups takes place to give the complexes (tmeda)Ni(?-ligand)n (n=1,2) and ethane.

The carbonylation of methanol to form methyl acetate and acetic acid was investigated using phosphine modified nickel iodide as the metal catalyst precursor. The course of the reaction was monitored using a high pressure, high temperature in situ Cylindrical Internal Reflectance FTIR reactor (CIR- REACTOR) to acquire data under autogenous conditions. The capabilities of the reactor permit reaction monitoring at temperatures of 190°C and pressures of 13.6 kPa (1500 psig). In this study the reaction kinetics and in situ observations were made at temperatures between ambient and 160°C with an operating pressure of 8.16 kPa (900 psig) for most reactions. This study used methyl acetate as a solvent, and both methyl acetate and acetic acid were products of the catalytic reaction. Conditions were optimized at 160°C using organo-phosphine modified NiI2 as the catalyst precursor. Under the applied reaction conditions, no anionic carbonyl species such as Ni(CO)(x)I(y)/(-y) were detected at high carbonylation rates, in contrast to the anionic carbonyls reported in the rhodium catalyzed acetic acid process. In the rapid kinetic regime, only trace amounts of Ni(CO)4 were formed in the reactor at steady state. The experimental results suggest a new mechanism involving Ni(PPh3)2 as one of the active metal complex intermediates reacting in a slow step with methyl iodide. The in situ reaction monitoring experiments readily enabled the determination of the concentrations of organonickel species as well as the concentration of carbonylation products under fast reaction conditions.

Cyclic voltammetry under CO has been used to show that the short-lived nickelocene anion splits into NiCp and Cp- (Cp = C5H5) fragments; trapping of the NiCp moiety with CO leads to -, which under high CO pressure loses a further Cp- to give Ni(CO)4.

The reaction of [Ni10C2(CO)16] 2- with Co3(μ3-CCl)(CO)9 results in the new bimetallic Ni-Co hexacarbido carbonyl clusters [H 6-nNi22Co6C6(CO)36] n- (n = 3-6), which possess polyhydride nature and can be interconverted by means of acid-base reactions. The tetra-anion [H 2Ni22Co6C6(CO)36] 4- and the hexa-anion [Ni22Co6C 6(CO)36]6- have been isolated in a crystalline state and structurally characterized via X-ray crystallography. The six carbide atoms are lodged into Ni7CoC square antiprismatic cages. Addition of strong bases to [Ni22Co6C6(CO) 36]6- affords mixtures of the monoacetylides [Ni 9CoC2(CO)16]3- and [Ni 9CoC2(CO)15]3-, which have been cocrystallized as [NEt4]3[Ni9CoC 2(CO)16-x] (x = 0.58-0.84) salts, displaying tightly bonded interstitial C2 units.

The reaction of nickelocene, 2 and its alkyne-substituted derivatives with Fe(CO)5, Fe3(CO)12 and alkyne-cluster derivatives of iron are reported and discussed.A considerable number of new heterometallic complexes has been obtained: the structures of the two tetranuclear complexes (η-C5H5)2Ni2Fe2(CO)7 (I) and (η-C5H5)2Ni2Fe2(CO)6(C2Et2) (IIa) have been determined by X-ray diffraction methods.Crystals of I are triclinic, a 8.028(8), b 14.561(12), c 7.961(8) Angstroem; α 94.58(7), β 97.26(11), γ 92.23(9)o; space group P.Crystals of IIa are triclinic, a 10.124(10), b 14.676(12), c 8.396(8) Angstroem; α 95.80(8), β 111.20(10), γ 72.89(9)o, space group P.Both structures have been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least-squares to R=0.039 for I and 0.045 for IIa.The structure of I is characterized by a tetrahedral metal atom core, bound to two cyclopentadienyl ligands (through the Ni atoms) and to six terminal CO's (through the Fe atoms).The seventh carbonyl is triply bridging between two Fe and one Ni atoms in an asymmetric way.The structure of IIa consists of a tetrahedrally distorted square arrangement of two Fe and two Ni atoms.The alkyne is ?-bonded to the Ni atoms and ?-bonded to the Fe atoms.The formation of heterometallic complexes in the above reactions is not selective, although the stability of the cluster reactants, and the nature of the bonding and the substituents in the alkynes can influence the nature and the yields of the products.

An active bifunctional nickel catalyst was prepared by decomposing Ni(CO)4 to highly dispersed metallic Ni onto Hβ zeolite and first applied in hydroconverting benzyloxybenzene (BOB), which was used as a lignin-related model compound. Ni/Hβ proved to be effective for converting BOB to bicyclic cyclanes (BCCs) via Calk–O bond cleavage induced by H+ addition, benzylium addition to 2- and 4-positions in phenol, hydrogenation of benzene ring, dehydration, and H? abstraction. Compared to one-step conversion, the total BCC selectivity (TBCCS) significantly increases from catalytic hydroconversion of catalytically converted BOB by pretreatment under pressurized N2.

We report a C?F reductive elimination from a characterized first-row aryl metal fluoride complex. Reductive elimination from the presented nickel(III) complexes is faster than C?F bond formation from any other characterized aryl metal fluoride complex.

A series of nickel(0) complexes, 3, 4, and 5, containing unsaturated 15-membered azamacrocyclic ligands have been synthesized. Structural characterization of the complexes is based on NMR spectroscopy, X-ray diffraction analysis, and differential scanning calorimetry. In addition, the catalytic activity of the complexes in the Suzuki-Miyaura cross-coupling of arylboronic acids and aryl halides has been tested.

The interactions of the nickel imine-amide allyl complex 1 with carbon monoxide and unsaturated hydrocarbons have been studied. It is shown that this complex reacts readily with carbon monoxide to form the nickel(0) diimine carbonyl complex [(2-(1-propenyl)-[1,10]phenanthroline)Ni(CO)2] 2. During the process the ligand undergoes a deep transformation within the nickel coordination sphere. Specifically, the nickel-nitrogen σ-bond turns to an N-donor bond with aromatization of a ring in the nitrogen-containing ligand. This novel heteroaromatic ligand 2-(1-propenyl)-[1,10]phenanthroline has been isolated; the nickel(0) diimine carbonyl complex 2 has been studied with X-ray diffraction method. The comparative spectral studies of complexes 1, 2, and 2-(1-propenyl)-[1,10]phenanthroline have been carried out with UV/vis, IR-FT, and 2D NMR spectroscopy. It has been shown that the planar 16-electron nickel(II) imine-amide allyl complex 1 is indifferent to olefins and acetylenes. Based on the NMR data, this fact can be explained by the inability of the π-δ rearrangement into 1.

The dinuclear Ni(ii)-Ni(i) complex NiII(dadtEt) NiI(SDmp)(PPh3) was synthesized as a Ni(ii) d-Ni(i)p model of the A-cluster in acetyl CoA synthase. This complex was reacted with Co(dmgBFsu

The reactivity of a nucleophilic nickel acylate complex with a tungsten carbene complex, Fe(CO)5, Cr(CO)6, PPh3, and CO was investigated. With the tungsten carbene complex, a methyl transfer occurred. With the metal carbonyl complexes, the acylate group on the nickel and a carbonyl on the iron or chromium traded places. With the PPh3 and CO, the acylate anion was replaced by the phosphine or CO ligand.

The ligand properties of cis,cis,cis-1,5,9-cyclododecatriene (c,c,c-cdt) have been explored. For the known (c,c,c-cdt)Ni (1b) and (c,c,c-cdt)(AgNO 3)3 (5) complexes and the new [(c,c,c-cdt)Cu(MeOH)]BF 4 (6b), [(c.c,c-cdt)Cu][Al{OC(CF3)3} 4] (6d), and (tBu2PC2H 4PtBu2)Ni(η2-c,c,c-cdt) (7b) complexes, the molecular structures have been determined. The c,c,c-cdt ligand in 5 and 7b retains the C2 symmetrical helical conformation of the free c,c,c-cdt, whereas in lb and 6b,d, it assumes a C3 symmetrical ratchet conformation. The coordination geometry of the metal in 6b is tetrahedral, and it is trigonal pyramidal in lb and 6d. Details of the synthesis and chemical and spectroscopic properties of the complexes are reported.

The ligand precursors P(CH2NH-3,5-(CF3) 2C6H3)3 (1a), P(CH 2NHPh)3 (1b), and P(CH2NH-3,5-Me 2C6H3)3 (1c), react with the reagents Ti(NMe2)4 and tBuN=Ta(NEt 2)3 to generate metal complexes of the type P(CH 2NArR)3TiNMe2 (2a-c) and P(CH 2NArR)3Ta=NtBu (3a-c) (where Ar R = 3,5-(CF3)2C6H3, Ph, and 3,5-Me2C6H3). Due to ring strain, the phosphine lone pair cannot chelate and is available to bind a second metal, and this feature can be utilized to synthesize heterometallic polynuclear complexes. The 31P chemical shifts observed upon complexation of the early transition metals to the amido donors are large and in the opposite direction expected for the increased C-P-C bond angles in these complexes; these unusual shifts are due to P-Ti and P-Ta distances that are significantly shorter than the sum of van der Waals radii. The reaction of 2c with Ni(CO)4 produces at first the bimetallic complex (CO)3Ni[P(CH 2N-3,5-Me2C6H3) 3TiNMe2] (4c), which gradually converts to the trimetallic complex (CO)2Ni[P(CH2N-3,5-Me2C 6H3)3TiNMe2]2 (5c). The effect of the complexation of Ti and Ta fragments on the donor ability of the phosphine ligand was determined by the preparation of the bis-phosphine complexes trans-L2Rh-(CO)Cl, (where L = 1a-c, 2a-c, and 3a-c) prepared by the reaction of the appropriate phosphine with [Rh(CO) 2-(μ-Cl)]2, and a measurement of the resultant CO stretching frequencies. Surprisingly, the complexes with the larger C-P-C angles are significantly poorer donors. Density functional theory calculations were performed to determine what factors affect the donor ability of the phosphine and if through-space interactions might play an important role in the observed electronic properties.

Reactions of the trinuclear complexes [Ni(RS3)] 3 [HS32- = bis(2-mercaptophenyl) sulfide(2-) (1a) or siS32- = bis(2-mercapto-3-trimethylsilylphenyl)sulfide(

The phosphines P(C6H4-4-SR)3 (R = H, Me, 2-C5H9O) and (C6H4 -4-SR)2PCH2CH2P(C6 H4-4-SR)2 (R = H, Me) have been synthesized. The phosphines with -SMe groups can be prepared by reaction of 4-BrC6H4SMe with either BuLi or magnesium (to generate the corresponding Grignard compound) followed by reaction with PCl3 or Cl2PCH2 CH2PCl2, respectively. The methyl group can be eliminated by reaction with sodium in liquid NH3. Other methods of protection/deprotection of the thiol group failed to afford the desired compounds. Reaction of 4-BrC6 H4SH with dihydropyrane afforded the protected thiol 4-BrC6H4S-2-C5H9O from which the corresponding phosphine was successfully synthesized. However, attempts to remove the tetrahydropyranyl group by reaction with AgNO3-HCl, gave an insoluble polymer as product. Reaction of P(C6H4SR)3 (R = H, Me) with Ni(CO)4 affords the corresponding mono phosphine complex quantitatively. The complex with the unprotected thiol group can be absorbed on a gold surface and the corresponding νCO bands were detected by grazing angle Fourier transform infrared reflection absorption spectroscopy (grazing angle FTIR-RAS). Reaction of Rh(acac)(CO)2 with P(C6H4SR)3 (R = Me) affords the complex Rh(acac)(CO)(P(C6H4SR)3) (R = Me), but if R = H a polymer insoluble in any solvent was obtained. The same occurs in the case of PtCl2(CO)(DMSO). Apparently, once P(C6H4SH)3 is coordinated to a metal not in the zero oxidation state, oxidation of the thiol group to disulphide becomes very easy even in a dinitrogen atmosphere.

The synthesis and characterization of three- and four-coordinate Ni(CO)n(NHC) (n = 2, 3; NHC = N-heterocyclic carbene) complexes are reported. Reactions with CO of the Ni(CO)2(NHC) complexes lead to the quantitative formation of Ni(C

The new organosulfur ligands siS3-H2 [siS32- = bis(2-mercapto-3-trimethylsilylphenyl) sulfide(2-)] and caS3-H2 [caS32- = bis(2-mercapto-3-carboxyphenyl) sulfide(2-)] were synthesized from HS3-H2 [HS32- = bis(2-mercaptophenyl) sulfide(2-)], n-butyllithium, and Me3SiCl or CO2/H+. Reaction of siS3-H2 with Ni(ac)2·4H2O gave the air-stable and well-soluble trinuclear complex [Ni(siS3)]3 (1) whose structure was determined by X-ray crystallography. Reactions of complex 1 with nucleophiles L [L = PR3 (R = nPr, Ph, Cy), N2H4, StBu-, and Cl-] yielded the corresponding neutral or anionic complexes, which were isolated as [Ni(PR3)(siS3)] [R = nPr (2), Ph (3), Cy (4)], Bu4N[Ni(Cl)(siS3)] (5), Bu4N-[Ni(StBu)(siS3)] (6), and [Ni(N2H4)(siS3)] (8). The azido complex Et4N[Ni(N3)(siS3)] (7) was prepared from Me3SiN3 and the precursor chloro complex Et4N[Ni(Cl)(siS3)]. Reaction of 1 with NH3 yielded labile [Ni(NH3)(siS3)] (9), which was characterized in solution by 1H and 13C NMR spectroscopy. Analogously, 1 reacts with nicotinamide (NA) or diethylnicotinamide (NAEt2) to give, from equilibrium reactions, the corresponding mononuclear [Ni(L)(siS3)] complexes with L = NA, NAEt2. X-ray structure determinations showed that 1, 3, 4, 5, and 7 all exhibit tetrahedrally distorted planar [Ni(L)(siS3)] fragments. Complex 7 is the first structurally characterized azidonickel complex with a coligand having exclusively sulfur donors. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.

The reactions of o-semiquinonediimine complexes M[o-(NH)(NPh)C6H4]2 (M = Ni (1) or Pt (2)) with carbonyl-containing iron and rhenium compounds were studied. The reactions of complexes 1 or 2 with Fe(CO)5 afforde

The nickel, copper, and silver metal carbonyl chloride molecules have been prepared and isolated in solid argon by cocondensation of the species generated from 1064 nm laser ablation of metal chlorides with carbon monoxide in excess argon at 11 K. On the

The reaction of '(bu)S2'2- = 3,5-ditertiarybutyl-1,2-benzenedithiolate(2-) with Ni(ac)2·4H2O and subsequently AsPh4Cl, yielded (AsPh4)2[Ni('(bu)S2')2] (1).

The hexacarbide clusters [H(6-n)Ni38C6(CO)42](n-) (n = 3, 4, 5, or 6) have been directly obtained from the reaction of [Ni6(CO)12]2- with C3Cl6, whereas the related anions, [H(6-n)-Ni32C6(CO)36](n-) (n = 5 or 6), have been obtained by degradation under carbon monoxide of [Ni38C6(CO)42]6-, or upon thermal treatment at ca. 110 °C of [Ni10C2(CO)16]2- salts. The compound [PPh3Me]6[Ni32C6(CO)36] · 4 MeCN is triclinic, space group P1 (No 2), with a = 15.974(3), b = 17.474(3), c = 18.200(4) A, α = 61.37(2), β = 69.31(2), γ = 72.35(2)°and Z = 1; final R = 0.033. The structure of [Ni32C6(CO)36]6- has an idealised O(h) symmetry and is based on a truncated octahedral Ni32C6 framework, with all edges spanned by bridging carbonyl groups. The six interstitial carbide atoms are lodged in square-antiprismatic cavities. The overall geometry of the Ni32C6 core is very similar to that found previously in [HNi38C6(CO)42]5-, and shows very close interatomic separations. Both [Ni32C6(CO)36]6- and [H(6-n)Ni38C6)(CO)42](n-) (n = 5 or 6) display electron-sink behaviour. Thus, they have been chemically and electrochemically reduced to their corresponding [Ni32C6(CO)36](n-) (n = 7-10), [Ni38C6(CO)42](n-) (n = 7-9) and [HNi38C6(CO)42](n-) (n = 6-8) derivatives, and several of the involved redox changes show features of electrochemical reversibility. In contrast, both [Ni32C6(CO)36]6- and [H(6-n)Ni38C6(CO)42](n-) (n = 5 or 6) support only one partially reversible oxidation step. Their different behaviour upon protonation or oxidation is an indirect, but unambiguous, proof of the hydride nature of [HNi32C6(CO)36]5- and [H(6-n)Ni36C6(CO)42](n-) (n = 3, 4, or 5), which could not be validated by 1H-NMR spectroscopy.

The formation of Ni(0)-norbornadiene-2,5 complexes, which are efficient catalysts for [2π + 2π]-cyclodimerization of norbornadiene-2,5 (NBD), was studied. The analysis of processes occurring during the induction period of the catalytic reaction of NBD and the results of elemental analyses of isolated intermediates suggest that the formation of true catalysts of NBD dimerization occurs in a similar manner if different initial nickel compounds are used. The true catalysts may be mononuclear homoligand nickel complexes with two or three NBD molecules as ligands. These complexes are in equilibrium with each other. The catalytic system formed from bis(η3-allyl)nickel is a convenient model for the ongoing research into the catalytic processes and process optimization.

The reaction of Fe2(CO)9 in thf with Ph2SbCH2SbPh2 (dpsm) or Me2SbCH2SbMe2 (dmsm) produced [Fe(CO)4(η1-dpsm)] and [Fe(CO)4(μ-dmsm)Fe(CO)4], and Co2(CO)8 reacted with either distibine ligand (L-L) to give [Co2(CO)4(μ-CO)2(μ-L-L)]. Ni(CO)4 and dpsm gave [Ni-(CO)3(η1-dpsm)] and [Ni(CO)3(μ-dpsm)Ni(CO)3], while with dmsm only [Ni(CO)3(μ-dmsm)-Ni(CO)3] was isolated. Mn2(CO)10 reacted slowly with dpsm or dmsm in the presence of a [{(Cp)Fe(CO)2}2] catalyst to give [Mn2(CO)8(L-L)], but no reaction occurred with Re2(CO)10 under similar conditions. cis-[Mn(CO)4X(dpsm)] (X = Cl, Br, or I) and [Mn2(CO)8Br2(μ-dmsm)] were also prepared from the appropriate [Mn(CO)5X], but iron carbonyl halide derivatives were too unstable to isolate in the pure state. The complexes have been characterized by elemental analysis, IR and multinuclear NMR (1H, 13C{1H}, 55Mn, or 59Co) spectroscopy, and FAB mass spectrometry. The X-ray structures of dpsm, [Fe(CO)4(η1-dpsm)], and [Co2-(CO)4(μ-CO)2(μ-dmsm)] have been determined. No evidence for chelation by dmsm or dpsm was found, and Sb-C fission does not occur to significant extents in the reactions studied.

A series of [M(L)('S2C')] complexes (M = NiII, PdII, PtII) containing the carbene dithiolate ligand 'S2C'2- = 1,3-imidazolidinyl-N, N′-bis(2-benzenethiolate)(2 - ) and various C and S co-ligands have been synthesized. When treated with KCN, n-butylisonitrile, the electron-rich olefin R2C=CR2 [ = bis(1,3-diphenylimidazolidine-2-ylidene)], LiMe, thiolates such as SEt-, SPh- or o-SC6H4NH2, and hydrogen sulfide, the parent complex [Ni('S2C')]2 · DMF (1) yields the corresponding anionic or neutral [Ni(L)('S2C')] complexes which were isolated as [K2(Kryptofix5)(THF)2(μ-OH2)][Ni(CN)('S2C')] (2), [Ni(CNBu)('S2C')] (3), [Ni(CR2)('S2C')] (4), [Li(12-crown-4)2][Ni(CH3)('S2C')] (5), [NBu4][Ni(SEt)('S2C')] · THF (6), [Na(15-crown-5)][Ni(SPh)('S2C')] (7), [Na(15-crown-5)][Ni(o-SC6H4NH2)('S2C')] · 0.5THF (8), and [Na(15-crown-5)][Ni(SH)('S2C')] (9). Analogous complexes of 9 have also been obtained with Pd (10) and Pt (11). The complexes were characterized by elemental analyses and the usual spectroscopic methods. X-ray structure determinations of 2, 3, 4, 6, 9 and 10 revealed that the [M('S2C')] fragments are stereochemically very rigid, being little influenced by the different co-ligands L. The four-coordinate metal centers exhibit an approximately square-planar coordination geometry. The 'S2C'2- ligands show a characteristic propeller-like twist resulting from positioning the C6 rings of the 'S2C' unit above and below the coordination plane. As evidenced by the molecular structures of 9 vs. 10, this twist can vary, and the 'S2C'2- ligand is flexible enough to accommodate also larger metal ions than NiII. Complexes 9-11 belong to the rare cases of isolable SH complexes. The complexes 2-11 exhibit a remarkable thermal stability (4 is stable up to 220°C), and the [M('S2C')] fragments so far proved inert towards decomposition. When treated with Broensted acids, the general reactivity feature of all anionic [M(L)('S2C')] complexes is release of HL and regeneration of the parent complexes [M('S2C')]2. The methyl complex [Li(4-crown-4)2][Ni(CH3)('S2C')] (5) is one of the rare examples in which a methyl ligand binds to an [NiS] center. While the parent complex [Ni('S2C')]2 · DMF (1) proved unreactive towards CO, 5 readily inserts CO yielding the highly reactive acetyl derivative [Ni(COCH3)('S2C')]-. This complex could not be isolated, but its formation was established by spectroscopic methods and by its subsequent reaction with PhSH yielding, among other products, the thioester CH3COSPh. The model character of this reaction sequence for acetyl-CoA synthesis catalyzed by CO dehydrogenases is discussed.

In quest of nickel complexes with sulfur ligation that model the acetyl-CoA synthase function of CO dehydrogenase (CODH), [Ni('S4C3Me2')] (1, 'S4C3Me2'2- = 1,3-bis(2-mercaptophenylthio)-2,2-dimethyl-propane-(2-)) was synthesized by template alkylation of Na2[Ni('S2')2] ('S2'2- = benzene-1,2-dithiolate(2-)) with CMe2(CH2Br)2. Acidic hydrolysis of 1 yielded the thiol "S4C3Me2"-H2 (2). Reduction of 1 with Na/Hg resulted in cleavage of the 'S4C3Me2'2- ligand and formation of the thermally stable trinuclear nickel(II) alkyl thiolato complex [Ni('μ-S2C3Me2')]3 (3, 'S2C3Me2' 2- = 1-(2-mercaptophenylthio)-2,2-dimethylpropyl(2-)). Treatment of 3 with L = Py, THF, or PMe3 afforded the mononuclear compounds [Ni('S2C3Me2')(L)] (4, L = Py; 5, L = PMe3). The stoichiometric reaction of [Ni('S2C3Me2')(L)] with CO led to the cyclic thioester 'S2C3Me2CO' (6, 'S2C3Me2CO' = 2,3-benzo-6,6-dimethyl-8-oxo-1,4-dithia-cyclooctane) and Ni(CO)4. In the analogous reaction of 5 with CO the intermediate nickel(II) acyl thiolato complex [Ni('S2C3Me2CO')(PMe3)] (7, 'S2C3Me2CO'(2-) = 1-(2-mercaptophenylthio)-2,2-dimethyl-3-oxobutyl(2-)) could be intercepted and fully characterized. The reaction of Ni(CO)4 with the thiol 2 yielded the starting Ni(II) complex 1 and allowed to close the reaction cycle that comprises the CODH sequence: [Ni] → [Ni-alkyl] → [Ni-acyl] → [Ni] + thioester. The net reaction can be formulated as 'S4C3Me2'-H2 (2) + CO → 'S2C3Me2CO' (6) + 'S2'-H2 and represents the first example of nickel mediated thioester formation in a complete reaction cycle. X-ray structure determinations of complexes 1,3,4, and 7 revealed approximately square planar coordination geometry for all Ni centers.

In situ IR monitoring of the Ni(CO)4/MeONA catalytic system for low temperature methanol synthesis has revealed the involvement of the [HNi(CO)3]- species in the catalysis. Two new methods for the synthesis of the anion were discovered and the model reactivity of [HNi(CO)3] - was also investigated. The overall results led us to suggest a catalytic cycle in which methanol is carbonylated to methyl formate with MeONa as the catalyst, while [HNi(CO)3]- catalyzes the hydrogenolysis of methyl formate to methanol.

Upon warming the reaction mixture of Ni(cdt), C2F4, and 2,6-iPr2Ph-dad in THF from -78 deg C to room temperature the red-violet complex (2,6iPr2Ph-dad)Ni(C2F4) (1) is obtained. 1 reacts with ethene already at -78 deg C by coupling of the olefinic ligands

The mixed-metal carbonyl cluster 3- was obtained by treating 2- with - in MeCN (molar ratio 2:1).It is rapidly degraded by carbon monoxide, at room temperature and atmospheric pressure, to 2-, and -.The salt 3 crystallizes in the monoclinic space group C2/c, with a = 20.525(9), b = 18.877(5), c = 42.713(4), β = 95.13(2) deg, and Z = 8.The structure was solved by conventional Patterson and Fourier methods and refined by full-matrix least squares to R = 0.045 and R' = 0.054 for 4545 independent reflections having I > 3.0?(I).The cluster consists of three almost parallel stacked triangles; the central unit contains the iridium atom, which achieves the highest metal-metal connectivity by rotating and translating the internal triangle.Each metal atom is bonded to one terminal CO and each intratriangular edge is spanned by one bridging carbonyl ligand.Average bond distances are Ir-Niinter 2.945, Ir-Niintra 2.522, Ni-Niinter 2.891 and Ni-Niintra 2.401 Angstroem.

Ni(CDT) dissolves in 1,6-heptadiene with displacement of the CDT to yield the dinuclear homoleptic product rac/meso-(μ-η2,η2-C7H12)(Ni(η2,η2-C7H12))2 (1) as a mixture of stereoisomers, in which the nickel atoms are trigonal-planar coordinated by a chelating 1,6-diene ligand and one C=C bond or a bridging diene ligand.The stereoisomers differ in the coordination mode of the bridging diene ligand. - The bridging diene ligand in 1 can be displaced by various donor/ acceptor molecules.In pentane, 1 reacts with ethene to yield a solution of mononuclear (C2H4)Ni(η2,η2-C7H12) (2).With alkynes unstable complexes are formed of which the anticipated ethyne derivative (C2H2)Ni(η2,η2-C7H12) (3) decomposes explosively at -100 deg C.With isocyanides, methylene phosphoranes, methyllithium, amines, pyridines, phosphanes, and phosphites (i.e.C, N, P donors) crystalline complexes of type L-Ni(η2,η2-C7H12) have been obtained, of which the derivatives with L = tBuNC 4, Me3PCH2 5, LiCH3 6, C7H13N 7, C5H5N 8, Me3P 9, iPr3P 10, Ph3P 11, (PhO)3P 12 are characterized here.For 11 the crystal structure has been determined.Key Words: Alkene ligands / 1,6-Dienes / Nickel complexes

The description of the reaction of Ni(CO)4-formation by means of the thermodynamics of irreversible processes is compared with the corresponding classic kinetic approach.The investigation of the reaction mechanism showed that the step determining the affi

In a further exploration of the types of high-nuclearity, mixed metal-(main-group) clusters accessible from the electron-rich 2- dianion (1), reactions of 1 (a direct descendent of nickel tetracarbonyl) with antimony and bismuth reag

Reaction of Ni(COD)2 with TBC in benzene affords a planar nickel(0) complex, Ni(TBC), with the nickel atom coordinated equally by all three alkynes of the TBC ligand. The reaction chemistry of moderately reversible. Ni(TBC) is reduced with lithium, sodium, and potassium in various solvents (THF and DME) in the presence of various chelating agents (TMEDA, 18-crown-6, and cryptand-(2.2.2)) to the monoanion and dianion. The material [K(C222)]2[Ni(TBC)] was combined with Ni(TBC) to yield a conducting material. The maximum conductivity (via two-probe power compaction) was observed to be 2 × 10-3 (Ω cm)-1 at 0.5 electron per Ni(TBC) unit. A parallel study on TBC showed a maximum conductivity of 8 (2) × 10-5 (Ω cm)-1 at 0.6 electron per TBC unit.

Ni(C2H4)3, Ni(cdt), or Ni(cod)2 react with tmeda and acrylic acid methyl ester, methyl vinyl ether, and acrylonitrile in ether to afford (tmeda)Ni(H2C=CHCOOCH3)2 (3, orange-red crystals), (tmeda)Ni(H2C=CHCOCH3)2 (4, red crystals), and (tmeda)Ni(H2C=CHCN)2

This article describes the low-temperature photochemistry of the complexes Ni(CO)2(tBu-DAB) (I) and Ni(CO)2(2,6-iPr2Ph-DAB) (II) in different media, in both the absence and the presence of a substituting ligand. The complexes differ in their molecular structure and in the character of their lowest MLCT transitions. The results of this study show that these differences are also responsible for the different primary photoprocesses taking place upon low-energy excitation. Irradiation into the MLCT bands causes breaking of a metal-nitrogen bond in the case of complex I and loss of CO for complex II.

Bis(μ-methyl-1,3-dimethyl-η3-allyl-nickel) which has been modified with chiral P ligands react with carbon monoxide to give the optically active 3-methyl-E-4-hexene-2-one.Low-temperature studies (DSC, 13C NMR) have indicated that this reaction is too fast to observe any intermediates.A suitable phosphine was chosen so that the chiral substituent is kept constant (1R,3R,4S-(-)-menthyl) and the other two are of the same, mostly achiral type (either P(-)MenthX2 or P(O(-)Menth)X2), the extent and direction of optical induction depends strongly on the concentration and the type of P ligand examined.Furthermore, changes in achiral parts of the P ligand after special order factors can lead to conversion into the excess enantiomer.Up to now the usual strategy to obtain the optical antipode has been to change the chirality of the educt.Therefore both enantiomers may be necessary.In our case only chiral precursor is needed and for this reason there is less need to draw from the natural pool, which should be useful for asymmetric synthesis.

Reduction of diluted solutions of anhydrous Ni(II) acetylacetonate in THF by reducing alkylating agents such as DIBAH, n-Bu Li or PrMgBr in the presence of carbon monoxide gave practically quantitative yields of Ni(CO)4.

Tris(ethene)nickel(0) reacts with tmeda and butadiene in ether below -40 deg C to yield a deep-red solution of (tmeda)Ni(η2-C4H6)2 (3a), from which red crystals of the thermolabile dinuclear complex 2-C4H6)>2(η2,η2-C4H6) (3b) can be separated.Results in the formation of mononuclear 3a, which also forms upon dissociation of 3b in solution, was identified from its 1H and 13C NMR spectra.Above -40 deg C, 3a,b decompose in solution, with coupling of the butadiene ligands to afford Ni(η3,η3,η2-C12H18), which was shown to be an intermediate of the nickel-catalyzed cyclotrimerisation reaction of butadiene.Thus 3a, b are the first butadiene complexes of nickel that are catalytically active despite the presence of stabilizing ligands.

The synthesis and properties of the new dicarbidocarbonyl bimetallic clusters 2- (I), 3- (II), and 3- (III), are described.Compound I, which is paramagnetic, has been synthesized in high yields by redox-condensation of Co3(CO)9CCl with 2-, whereas the diamagnetic trianions II and III have been respectively obtained by reduction of I, with sodium metal in THF and sodium hydroxide in methanol.The anion I has been isolated in a crystalline state in association with several tetrasubstituted ammonium or phosphonium cations, which are characterized by elemental analysis and by a single-crystal X-ray diffraction study, of the tetraphenylphosphonium salt.The anion I has a metal frame based on a 3,4,3-C2h stack of metal atoms, which may be regarded as derived by condensation of two either octahedral or trigonal-prismatic moieties.The resulting deca-vertices metal polyhedron encapsulates a C2 fragment showing a short C-C interatomic separation of 1.48 Angstroem.The three cobalt atoms cannot be distinguished from the remaining seven nickel atoms and are probably randomly distributed over the ten vertices.The M-M distances are scattered over the range 2.34-2.80 Angstroem, and each carbide carbon is encapsulated in a seven-vertices cage which may be described as a distorted capped trigonal prism.The carbonyl stereochemistry comprises six carbonyl groups terminally bonded to the atoms of the top and bottom triangular layers, and ten edge-bridging CO which span the ten inter-layer edges.The structure of this decanuclear dicarbide cluster is compared with those reported for related species and a rationalization is offered for the variations of the metal geometry and the C-C interatomic separation.