Reaktionen von Gemischtligand-Komplexen des Nickel(0) mit Kohlenstoffdichalcogeniden

Reactions of Mixed Ligand Complexes of Nickel(0) with Carbon Dichalcogenides Decisive for the occurrence of a reaction between mixed ligand complexes of nickel(0) and carbon dichalcogenides is the HOMO-energy of the complex and the LUMO-energy of the reagent, which are reflected in the corresponding polarographic half-wave potentials. Therefore, (dipy)-Ni(COD) is substituted by SeCS, CS₂ and SCO, whereas (PPh₃)₂Ni(C₂H₄) only reacts with CS₂, but not with SCO. Substitution by CO₂ needs substrates like Ni(PCy₃)₃ or Ni(PEt₃)₄ which have the lowest anodic waves. (PCy₃)₂Ni(C₂H₄) and (dipy)Ni(PPh₃)₂ effect C?S-bond breaking in SCO, and mixed carbonyls, such as (PCy₃)₂Ni(CO)₂ or (PPh₃)₂Ni(CO)₂, are formed. Futher products are dithiocarbonates or oligonuclear nickel sulfides which are stabilized by a phosphine. Another oligonuclear complex, (PPh₃)₂Ni₃(CS₂)₂, is formed by the reaction of CS₂ with surplus (PPh₃)₂Ni(C₂H₄). The function of CS₂ is that of a bridging ligand. The carbon dichalcogenides are side-on (η²) coordinated in compounds like (dipy)Ni(CS₂), (PPh₃)Ni(CS₂) and (dipy)Ni(SCO). It is always the highest electronegative heteroatom of the non symmetric ligands SeCS and SCO which does not interact with the central atom.     

ESR Study of the Reaction between the Ni(PPh3)4Complex and Brönsted Acids

The reaction of Ni(PPh₃)₄with acetic and trifluoroacetic acids is studied by ESR. When Ni(PPh₃)₄reacts with protonic acids, oxidative addition of the acid to the Ni(0) occurs along with contradisproportionation of the formed Ni(II) complexes with the Ni(0) complex. As a result, stable Ni(I) carboxylate complexes (PPh₃)₃Ni–OOCR are formed, where R = CH₃, CF₃. The amounts of the formed Ni(I) carboxylate complexes and of the evolved hydrogen were found to depend on the rate of acid addition to the Ni(0) complex.     

Nickel(II) N‐Benzyl‐N‐methyldithiocarbamato Complexes as Precursors for the Preparation of Graphite Oxidation Accelerators

The nickel(II) N‐benzyl‐N‐methyldithiocarbamato (BzMedtc) complexes [Ni(BzMedtc)(PPh₃)Cl] ( 1 ), [Ni(BzMedtc)(PPh₃)Br] ( 2 ), [Ni(BzMedtc)(PPh₃)I] ( 3 ), and [Ni(BzMedtc)(PPh₃)(NCS)] ( 4 ) were synthesized using the reaction of [Ni(BzMedtc)₂] and [NiX₂(PPh₃)₂] (X = Cl, Br, I and NCS). Subsequently, complex 1 was used for the preparation of [Ni(BzMedtc)(PPh₃)₂]ClO₄ ( 5 ), [Ni(BzMedtc)(PPh₃)₂]BPh₄ ( 6 ), and [Ni(BzMedtc)(PPh₃)₂]PF₆ ( 7 ). The obtained complexes 1 – 7 were characterized by elemental analysis, thermal analysis and spectroscopic methods (IR, UV/Vis, ³¹P{¹H} NMR). The results of the magnetochemical and molar conductivity measurements proved the complexes as diamagnetic non‐electrolytes ( 1 – 4 ) or 1:1 electrolytes ( 5 – 7 ). The molecular structures of 4 and 5· H₂O were determined by a single‐crystal X‐ray analysis. In all cases, the Ni^II atom is tetracoordinated in a distorted square‐planar arrangement with the S₂PX, and S₂P₂ donor set, respectively. The catalytic influence of selected complexes 1 , 3 , 5 , and 6 on graphite oxidation was studied. The results clearly indicated that the presence of the products of thermal degradation processes of the mentioned complexes has impact on the course of graphite oxidation. A decrease in the oxidation start temperatures by about 60–100 °C was observed in the cases of all the tested complexes in comparison with pure graphite.     

Triphenylphosphan-Nickel(0)-Komplexe mit Isocyanid-Liganden — [(RNC)nNi(PPh3)4–n] (n = 1–3)

Triphenylphosphane Nickel(0) Complexes with Isocyanide Ligands — [(RNC)_nNi(PPh₃)_4–n] (n = 1–3) Synthesis and properties of the isocyanide triphenylphosphane nickel(0) complexes [(RNC)Ni(PPh₃)₃], [(RNC)₂Ni(PPh₃)₂] and [(RNC)₃Ni(PPh₃)] (R = ^tBu, Cy, PhCH₂, p-TosCH₂) are described. I.r. and ³¹P n.m.r. spectra were recorded and the X-ray crystal structure of [(PhCH₂NC)₂Ni(PPh₃)₂] was determined.     

Nickel(II) di(pentyl)dithiocarbamates with P ligands

Ni(II) di(pentyl)dithiocarbamates of composition [Ni(Pe₂dtc)₂], [NiX(Pe₂dtc)(PPh₃)] (X = Cl, Br, I, NCS), [Ni(NCS)(Pe₂dtc)(PBut₃)], [Ni(Pe₂dtc)(PPh₃)₂]ClO₄ and [Ni(Pe₂dtc)(PPh₃)₂]PF₆ (Pe₂dtc = di(pentyl)dithio-carbamate, PPh₃ = triphenylphosphine, PBut₃ = tributylphosphine) have been synthesized. The complexes have been characterized by the usual methods. X-ray structure analyses confirmed the nature of [NiI(Pe₂dtc)(PPh₃)] and [Ni(Pe₂dtc)(PPh₃)₂]ClO₄ complexes.     

Redox properties of the nickel(II),(I),(0)-triphenylphosphine system in acetonitrile

The cathodic behaviour of electrochemically generated nickel(II) has been investigated in acetonitrile in the presence of triphenylphosphine at a platinum electrode. An appropriate combination of voltammetric, spectrophotometric and NMR findings has allowed us to establish that Ni(II) is present in solution as [Ni(PPh₃)₂ (CH₃CN)₄^2+.]. For the reduction of this species an EECE mechanism is proposed which is consistent with the data. It undergoes an irreversible two-electron reduction giging the Ni(0) complex [Ni(PPh₃)₄] which reacts quickly with the depolarizer. In this last homogeneous redox reaction the not previously reported Ni(I) complex [Ni(PPh₃)₄⁺] is obtained. The degree of reversibility of the redox processes involved has been discussed taking into account the structure, the coordination number and the nature of the ligands in both the redox partners.     

茚基镍的卤化物/四苯硼钠/三苯基膦体系催化苯乙烯聚合

The catalytic activity of a series of indenylnickel（Ⅱ） halides： （1-R-Ind）Ni（PPh3）X （R=ethyl, cyclopentyl and benzyl, while X=Cl, Br and I）, towards styrene polymerization was studied in the presence of NaBPh4 and PPh3. The catalytic property of these halides was related to the substituent group on the indenyl ligand and the halogen atom bonded to the metal atom. Among them, the （1-Et-Ind）Ni（PPh3）Cl/NaBPha/PPh3 system showed the highest activity for the polymerization of styrene, and the polystyrene obtained was a syndio-rich （rr triad） atactic polymer with Mn values in the range of 103--104. The mechanism of the styrene polymerization initiated by the （1-Et-Ind）Ni（PPh3）Cl/NaBPha/PPh3 system was studied.     

Ni(II) complexes of unsymmetrical phenyl and phenethyl dithiocarbamates and triphenylphosphine

Unsymmetrical Ni(II) complexes of phenyl- and phenethyldithiocarbamate and PPh₃ of composition [NiX(HPhdtc)(PPh₃)], [NiX(HPhetdtc)(PPh₃)], [Ni(HPhdtc)(PPh₃)₂]ClO₄ and [Ni(HPhdtc)(PPh₃)₂]PF₆ {X?=?Cl, Br, I, NCS; HPhdtc?=?phenyldithiocarbamate, HPhetdtc?=phenethyldithiocarbamate, PPh₃?=?triphenylphosphine} have been synthesized. The complexes have been characterized by elemental and thermal analysis, IR and electronic spectroscopy, magnetochemical and conductivity measurements. Single-crystal X-ray analysis of [NiBr(HPhdtc)(PPh₃)]?·?CHCl₃ confirmed a distorted square planar coordination for the NiS₂PBr chromophore. For selected samples, the catalytic effects of graphite oxidation were studied.     

Nickel complexes of phosphine-appended benzannulated boron heterocycles

We report the synthesis and characterization of two diphosphine nickel complexes containing 9-borafluorene (PBFlu, 9-(diisopropylphosphino)phenyl-9-borafluorene) and 9,10-dihydroboranthrene (B₂P₂, 9,10-bis(2-(diisopropylphosphino)phenyl)-9,10-dihydroboranthrene) cores. Metalation of PBFlu and B₂P₂ with Ni(PPh₃)₄ leads to the monometallic complexes (PBFlu)Ni(PPh₃) and (B₂P₂)Ni, respectively. Cyclic voltammetry studies show a reversible redox event at ～0.1?V and a quasi-reversible event at ca. ?3?V versus ferrocene/ferrocenium for (B₂P₂)Ni while (PBFlu)Ni(PPh₃) features no reversible redox events. Electronic structure calculations were performed to provide further insight into the bonding in these complexes.     

Hydrosilylation and double silylation of carbonyl compounds with 1,1′-bis(dimethylsilyl)ferrocene using nickel- and platinum-catalysts

A series of ferrocene-based organosilicon compounds have been prepared via hydrosilylation or double silylation of carbonyl compounds with 1,1′-bis(dimethylsilyl)ferrocene using (C₂H₄)Pt(PPh₃)₂ or Ni(PEt₃)₄ catalysts. In general, while the platinum catalyst (C₂H₄)Pt(PPh₃)₂ preferentially produced cyclic double-silylated products, the Ni(PEt₃)₄ catalyst led to the hydrosilylated ferrocene products from aldehydes or ketones.     

Monometallic Ni0 and Heterobimetallic Ni0/AuI Complexes of Tripodal Phosphine Ligands: Characterization in Solution and in the Solid State and Catalysis

The tridentate chelate nickel complexes [(CO)Ni{(PPh₂CH₂)₃CMe}] ( 2 ), [(CO)Ni{(PPh₂CH₂CH₂)₃SiMe}] ( 6 ), and [Ph₃PNi{(PPh₂CH₂CH₂)₃SiMe}] ( 7 ), as well as the bidentate complex [(CO)₂Ni{(PPh₂CH₂)₂CMeCH₂PPh₂}] ( 3 ) and the heterobimetallic complex [(CO)₂Ni{(PPh₂CH₂)₂CMeCH₂Ph₂PAuCl}] ( 4 ), have been synthesized and fully characterized in solution. All ¹H and ¹³C NMR signal assignments are based on 2D‐NMR methods. Single crystal X‐ray structures have been obtained for all complexes. Their ³¹P CP/MAS (cross polarization with magic angle spinning) NMR spectra have been recorded and the isotropic lines identified. The signals were assigned with the help of their chemical shift anisotropy (CSA) data. All complexes have been tested regarding their catalytic activity for the cyclotrimerization of phenylacetylene. Whereas complexes 2 – 4 display low catalytic activity, complex 7 leads to quantitative conversion of the substrate within four hours and is highly selective throughout the catalytic reaction.     

Influence of the order of introduction of protonic acids on the formation of active complexes in the Ni(PPh3)4/BF3 · OEt2 catalytic system

The influence of the order of introduction of promoters (complex protonic acids) on the formation of active complexes in the Ni(PPh₃)₄/BF₃ · OEt₂ catalytic system and the activity of these systems in ethylene oligomerization have been studied. The activity of the systems in which nickel exists mainly as cationic Ni(I) complexes is more than one order of magnitude higher than the activity of the systems where nickel exists mainly in the form of Ni(II) hydride complexes. The role of alcohols as promoters in the Ni(PPh₃)₄/BF₃ · OEt₂ catalytic system is elucidated. The alcohols are the source of Ni(II) hydrides and, more importantly, the source of strong Brønsted acids, which efficiently ensure the coordinative unsaturation of the cationic Ni(I) complexes.     

Synthesis and Characterization of Homoleptic and Heteroleptic Complexes Involving Dithiocarbamates,Triphenylphosphine, and Nickel(II)

Abstract

Six new nickel complexes of two dithiocarbamate ligands (cyfdtc = N-cyclohexyl-N- furfuryldithiocarbamate and bztpedtc = N-benzyl-N-[2-thiophenylethyl]dithiocarbamate) namely, (Ni[cyfdtc]₂) (1), (Ni[bztpedtc]₂) (2), (Ni[cyfdtc][NCS][PPh₃]) (3), (Ni[bztpedtc] [NCS][PPh₃]) (4), (Ni[cyfdtc][PPh₃]₂)ClO₄ (5), and (Ni[bztpedtc][PPh₃]₂)ClO₄ (6) have been prepared and characterized using IR, electronic, and NMR (¹H and ¹³C) spectra. A single crystal X-ray structural analysis was carried out for complex 3 and showed that nickel is in a distorted square planar arrangement with the NiS₂PN chromophore. The shift in ν_C?N of the heteroleptic complexes to higher frequencies compared with the parent complex is assigned to mesomeric delocalization of electron density from the

dithiocarbamate ligand toward the metal atom, which increases the contribution of polar thioureide form in mixed ligand complexes. Electronic spectral studies suggest square planar geometry for the complexes. In the ¹³C NMR spectra, the upfield shift of NCS₂ carbon signal for 3 and 4 from the chemical shift value of 1 and 2 is due to effect of PPh₃ on the mesomeric drift of electron density toward nickel throughout thioureide C?N bond.     

Bimetallic complexes with porphyrins containing a cyclometalated phenylpyridine group

Treatment of Ni(HP¹) (H₃P¹ = meso-5-[4′-(2″-pyridyl)phenyl]-10,15,20-triphenyporphyrin) with K₂[PdCl₄] in EtOH afforded [Pd{Ni(P¹)}]₂(μ-Cl)₂ that reacted with NaS₂CNEt₂ to give Pd(S₂CNEt₂)[Ni(P¹)]. Reaction of Ni(HP¹) with [Ir(H)₂(PPh₃)₂(Me₂CO)₂][BF₄] afforded Ir(H)Cl(PPh₃)₂[Ni(P¹)]. The crystal structures of Pd(S₂CNEt₂)[Ni(P¹)] and Ir(H)(Cl)(PPh₃)₂[Ni(P¹)] have been determined.     

Zur Oxydation von Gemischtligand-Nickel(0)-Komplexen mit organischen Halogeniden

Oxidation of Mixed Ligand Nickel(0) Complexes by Organic Halides The oxidation of (dipy)Ni(PPh₃)₂ by alkyl and aryl iodides or bromides affords the nickel(I) complexes (dipy)Ni(PPh₃)X (X = Br, I). No normal products of oxidative addition are obtained. But in the case of methyl and ethyl halides complexes of the type (dipy)NiR₂ are formed as intermediates. Basing on the identified final products and on the correalation between the reactivity of the organic halides and their polarographic half wave potentials a mechanism of the reaction is proposed. The first step is a charge transfer from nickel(0) to the organic halide. Further synthesis, reactions, and the ESR-spectra of the complexes (dipy)Ni(PPh₃)X and a synthesis of (dipy)Ni(CH₂Ph)₂ are described. Experiments to prepare pure (dipy)Ni(PPh₃)Cl had no success.     

Über die natur der übergangsmetall-kohlenstoff-σ-bindung: IX. Über die darstellung und charakterisierung von η5-cyclopentadienyl-triphenylphosphin-nickel-η1-thioanisolyl und seine thermische zersetzung in nickelthiophenolatokomplexe

The reaction of Cp(PPh₃)NiCl (Cp = η⁵-C₅H₅) with PhSCH₂Li gives Cp(PPh₃)Ni(η¹-CH₂SPh) (I), which has been isolated as green crystals and characterized by elemental analysis, magnetic measurement, ¹H NMR and mass spectroscopic investigations and by protolysis to form PhSCH₃. Cp₂Ni also reacts with PhSCH₂Li in the presence of PPh₃ to give I containing 5–10% of Cp(PPh₃)NiSPh (II) and about 1% of [CpNiSPh]₂ (III) as impurities. In the absence of PPh₃, III is formed, with the release of ethylene and cyclopropane, even at a temperature of ?20°C. For comparison, II has been synthesized from Cp₂Ni, PPh₃ and LiSPh and from the reaction of III with PPh₃.I decomposes in boiling benzene to give II (ca. 33%) and III (ca. 13%). The conversion of the thioanisolyl into thiophenolato complexes can be understood on assuming that {CpNi(η²-CH₂SPh)} is formed as an unstable intermediate.     

Reactions of Aluminium Tribromide with Tetrakis(triphenylphosphine)nickel(0) and Tetrakis(triethylphosphite)nickel(0) Complexes

Reactions of aluminium tribromide with the Ni(0) phosphine and phosphite complexes are studied by EPR method. AlBr₃was found to cause the oxidation of the transition metal in the (PPh₃)₄Ni complex to the univalent state with the formation of the tetracoordinated (PPh₃)₃NiBr complex. With an excess of AlBr₃, the phosphine ligands are eliminated from the coordination sphere of Ni(I), and the coordinatively unsaturated complexes are destroyed to give the colloidal nickel. In the reaction of (P(OEt)₃)₄Ni with AlBr₃, Ni(0) is also oxidized to Ni(I), but the acido ligand is not eliminated even with a 15-fold excess of the Lewis acid. The activity of catalytic systems on the basis of the Ni(0) phosphine complexes and the Lewis acids in the low-molecular oligomerization reactions of olefines is determined by the cationic coordinatively unsaturated Ni(I) complexes formed in these systems.     

Formation and nature of catalysts based on nickel(0) phosphine complexes active in lower alkene dimerization and oligomerization

The catalytic properties and formation mechanism of alkene dimerization-active complexes in systems based on Ni(PPh₃)₄ and boron trifluoride etherate are considered. The nature of the modifying action of Brønsted acids on the properties of metal complex catalysts for propylene dimerization is reported. The interaction between Ni(PPh₃)₄ and BF₃ · OEt₂ is influenced by water. Depending on the water concentration, the reaction can proceed via formally one-electron oxidation to yield cationic Ni(I) complexes or via two-electron oxidation to yield Ni(II) hydrides. The catalytically active species in alkene dimerization and oligomerization in these systems are Ni(II) hydrido complexes.     

Metal complexes in the catalytic reactions of olefins. 1. Comparison of the catalytic properties of triphenylphosphine nickel complexes both individually and heterogenized on Al2O3 in the dimerization of ethylene

Conclusions By studying the liquid-phase dimerization of ethylene in the presence of Cat-Et₃Al₂-Cl₃ catalytic systems based on a nickel complex heterogenized on Al₂O₃ and a number of model nickel complexes, a similar activity and selectivity of the process has been established (Cat=NiPPh₃(CO)₂L, where L=PPh₃, CO, Al₂O₃; Ni(PPh₃)₂(CO)₂; Ni(PPh₃)₂(₂-C₂H₄); Ni[P(C₆H₁₁)₃]₂(H)Cl and Ni(PPh₃)(Et)Cl).The results of the investigation agree with the hypothesis that mono- and diolefinic nickel complexes are formed as the active intermediates in the reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2466–2469, November, 1988.     

Catalysis of dimerization and oligomerization reactions of lower alkenes by systems based on Ni(PPh3)2(C2H4) and Ni(PPh3) n Cl (n = 2 or 3)

The catalytic characteristics of the individual complex Ni(PPh₃)₂(C₂H₄) and Ni(PPh₃) _n Cl (n = 2 or 3) and those of systems based on these complexes in combination with Brönsted and Lewis acids in ethylene and propylene oligomerization have been determined. A correlation between the BF₃ · OEt₂ solution storage time and the catalytic properties of the nickel systems has been established for the reactions of the lower alkenes. The observed increase in the turnover frequency and turnover number of the catalyst is due to the increase in the Brörsted acid concentration as a result of irreversible conversions of BF₃ · OEt₂ caused by its interaction with impurity water in the solvent. The formation of the Ni(PPh₃)₂(C₂H₄)-BF₃ · OEt₂ catalytic system in the presence of a substrate dramatically extends the system’s service life. The interaction of the nickel precursors with boron trifluoride etherate has been investigated using a complex of physical methods, and the main reactions yielding catalytically active species have been revealed.