Organometallchemie binuclearer 1-Azadien-nickel(0)-Komplexe Bimetallverbindungen mit Ni?Fe-Bindung durch Addition von Pentacarbonyleisen(0) und Nickelalactone durch Ringöffnung cyclischer Anhydride

Organometallic Chemistry of Binuclear 1-Azadiene-Nickel(0) Complexes: Bimetallic Compounds with a Ni? Fe Bond by Addition of Pentacarbonyl-iron(0) and Nickelalactons by Ring Opening Reaction of Cyclic Anhydrides The binuclear nickel(0) complexes 1–3 , which contain as well bridging 1-azadienes ligands as five or six-membered (N∩N)-chelate rings react at ?30°C with Fe(CO)₅ to form the bimetallic compounds 4–6 , containing a Ni? Fe bond and two carbonyl groups as bridging ligands. The coordination of the [(bpy)Ni(0)] fragment to the olefin part of the 1-azadiene chain in 6 leads to the formation of the trinuclear complex 7 , which can storage CO₂ at the peripheral position. Succinic acid anhydride or glutaric acid anhydrid undergo a ring opening reaction by reacting with 3 yield nickelalactones upon elimination of CO.     

Bis‐NHC Chelate Complexes of Nickel(0) and Platinum(0)

For a long time d¹⁰‐ML₂ fragments have been known for their potential to activate unreactive bonds by oxidative addition. In the development of more active species, two approaches have proven successful: the use of strong σ‐donating ligands leading to electron‐rich metal centers and the employment of chelating ligands resulting in a bent coordination geometry. Combining these two strategies, we synthesized bis‐NHC chelate complexes of nickel(0) and platinum(0). Bis(1,5‐cyclooctadiene)nickel(0) and ‐platinum(0) react with bisimidazolium salts, deprotonated in situ at room temperature, to yield tetrahedral or trigonal‐planar bis‐NHC chelate olefin complexes. The synthesis and characterization of these complexes as well as a first example of C? C bond activation with these systems are reported. Due to the enforced cis arrangement of two NHCs, these compounds should open interesting perspectives for bond‐activation chemistry and catalysis.     

Selektive Cyclotetramerisierung von Propargylalkohol: katalytische Reaktionen hoher Selektivität und Geschwindigkeit an Nickelkomplexen

Selective Cyclotetramerization of Propargylic Alcohol: Catalytic Reactions with High Selectivity and Reaction Rate by Nickel Complexes It is shown propargylic alcohol reacts with different nickel catalysts to form cyclotetrameres in a selective reaction. Main product of the reaction is 1,3,5,7-tetrakis(hydroxymethyl)-cycloocta(1,3,5,7)-tetraene. The reaction is extremely fast; when it is carried out without solvents at 114°C turnover numbers of 10⁶ catalytic cycles/mol Ni × h can be observed. The influence of phosphines is different: In solvents aromatic compounds, and cyclotetrameres are formed, when solvents are not used, phosphines have no controlling effect. The reaction can also be catalyzed by iron complexes to form cyclotetrameres, cobalt complexes yield a mixture of cyclotrimeres and cyclotetrameres. Supported Nickel or Raney-Nickel can also catalyze the cyclotetramerization. The investigations show that the 1-azadiene ligands in bis(cinnemaldehydeanil)-nickel(0) are substituted by propargylic alcohol in a fast reaction. After the substitution the catalytic reaction takes place at “ligand free nickel”.     

1,4-Diazabuta-1,3-dien-N-Sulfinylamin-Nickel(0)-Komplexe

1,4-Diazabuta-1,3-Diene-N-Sulfinylamin Nickel(0) Complexes Synthesis, properties, and reactions of 1,4-diazabuta-1,3-diene-N-sulfinylamine nickel(0) complexes are described. The highly coloured and extremely air and moisture sensitive nickel(0) complexes have been characterized by means of i.r. and ¹H n.m.r.spectroscopy. The N-sulfinylamine ligands are η²-(S,N)-side on coordinated.     

Cyclische α,β-ungesättigte Carbonylverbindungen als Liganden in Nickel(0)-Komplexen

Cyclic α, β-Unsaturated Carbonyl Compounds as Ligands in Nickel (0) Complexes . As a result of the reaction of (Cy₃P)₂Ni(C₂H₄) with p-benzoquinone (p-CH) or maleic anhydride (MSA), nickel(II)-complexes of radical anions are formed which are derived from PCy₃ and p-CH or MSA by an equimolecular coupling. With other cyclic α, β-unsaturated carbonyl compounds (L = 1,4-naphthoquinone, substituted α- and γ-pyrones, substituted coumarins) no comparable reactions proceed in the coordination sphere of nickel(0) phosphine complexes. But depending on the phosphine and on the substrate compounds of the types (R₃P)₂NiL or (R₃P)NiL are obtained. Taking the substituted coumarins for an example, it was demonstrated that the latter type is favoured by bulky phosphines (PCy₃) and by coumarins with a high π-acceptor strength. The i.r. spectra of the complexes (R₃P)NiL are in accordance with an η³(C?C,O)-bridging function of α, β-unsaturated carbonyl ligands and therefore with an oligomeric structure. For the complexes (R₃P)₂NiL and (dipy)NiL an η²(C?C) or a pseudo-η³ (C?C,C) coordination of the ligands is discussed. Of special interest are the compounds (Cy₃P)Ni(DMP) and (Cy₃P)Ni(BDH) (DMP = 2, 6-dimethyl-γ-pyrone, BDH = 2-benzylidene-1, 3-dioxo-hydrindene). Possibly the substituted γ-pyrone is an η⁶-ligand in (Cy₃,P)Ni(DMP). (Cy₃,P)Ni(BDH) is considered to be a nickel(II) chelate of a diva-lent anion which is derived from BDH by the uptake of two electrons. In this connection the limits for a classification of the new complexes as nickel(0) or nickel(II) compounds are mentioned. The polarographic half-wave potentials are applied to an estimation of the reactivity of the α, β-unsaturated carbonyl compounds related to nickel(0) complexes.     

Metall(0)-Komplexe von Nickel und Molybdän mit Benzil-bis-phenyliminen als Chelatliganden

Metal(0) Complexes of Nickel and Molybdenum with Benzil-bis-phenylimines as Chelateligands Benzil-bis-phenylimines form with Mo(CO)6 stable tetracarbonylcomplexes; their spectroscopical behaviour shows, that the ligands are π-electron acceptors. Substitution by R₃P gives tricarbonylcomplexes. Some nickel(0) complexes (NiL₂, Ni(R₃P)L) are described. The magnetical and spectrophotometrical properties of these chelatcomplexes are investigated.     

Nickel(II) and cobalt(II) complexes of methyl(2-aminocyclopentene-1-dithiocarboxy)-S-acetate (ACDASAMe)

Nickel(II) and cobalt(II) bis-chelates of methyl(2-aminocyclopentene-1-dithiocarboxy)-S-acetate (ACDASAMe) were synthesized and characterized by spectroscopic methods and in the case of the nickel complex, X-ray single-crystal diffraction. The ligand exhibits the (N, S) coordination mode on interacting with the metal centers. The X-ray structure of the nickel(II) complex reveals a NiN₂S₂ distorted square planar coordination geometry with the ligands showing a cis configuration. There is no interaction between the –CH₂COOMe moieties of the ligand and the metal center, however intermolecular hydrogen bonds through the carbonyl group leads to the building of dimeric associations.     

Nickel(II)‐Komplexe von Oxalamidinen und Oxalamidinaten mit zusätzlichen R2P‐Donorgruppen

Complexes of Nickel(II) with Oxalic Amidines and Oxalic Amidinates with Additonal R₂P‐Donor Groups Oxalamidines R¹N=C(NHR²)‐C(=NHR²)=NR¹, which bear additional donor atoms at two of the four N substituents ( H₂A : R¹ = mesityl, R² = ‐(CH₂)₃‐PPh_2; H₂B : R¹ = tolyl, R² = ‐(CH₂)₃‐PMe₂) form binuclear complexes with Nickel(II) in which very different coordination modes are realized. In the complex [ (A) Ni₂Br₂] (1) the two nickel atoms at each side of the bridge are in a square‐planar environment, coordinated by the two N donor atoms of the oxalic amidinate framework, a bromide and a Ph₂P group. An analogous coordination has the organometallic compound [ (A) Ni₂Me₂] (2) . In contrast, the two nickel atoms in the compound {[( B )][Ni(acac)]₂} (5) differ in their coordinative environment. At one side of the oxalic amidinate bridging ligand a (acac)Ni fragment is coordinated by the two N donor atoms resulting in a square‐planar environment. At the opposite side the (acac)Ni fragment is coordinated at the both N donor ligands of the bridging ligand as well as at the two PMe₂ groups of the side chains resulting in an octahedral coordination for this nickel atom.     

Tetraazamacrocyclic Nickel(II) Complexes Containing a Pendant Amino Group

Reduction of the nitro group in 5-nitromethyl-1,4,8,11-tetraazacyclotetradeca-11-enenickel(II) complexes 1 leads to 5-aminomethyl-substituted macrocyclic nickel(II) complexes. Orange, protonated “arm off” (3 and 5) and violet “arm on” (2 and 4) complexes were isolated and characterized. Relative configurations of substituents and conformations of the macrocyclic ligands are proposed on the basis of NMR evidence. The isolation of free ligands is also described.     

Strukturuntersuchungen an Derivaten des Nickelkomplexes Ni(ONO) (ONO2− = Dianion einer dreizähnigen Schiffschen Base)

Structure Studies on Derivatives of the Nickel Complex Ni(ONO) (ONO^2? = Dianion of a Tridentate Schiff Base) The thermodynamically stable form of the solvent free, formally tri-coordinate complex Ni(ONO) (ONO^2? = dianion of N-(2-hydroxyphenyl)-2-ethoxycarbonyl-3-ox(o-butene(1) amine(1)) as well as the mono adducts Ni(ONO)X with X = ammonia and X = diphenyl thiourea (DPT) have been characterized by X-ray structure analysis. In all cases the central atom is coordinated in a square-planar fashion, only for the adduct Ni(ONO)(DPT) a pyramidal distortion is observed which is due to the formation of hydrogen bonds. The solvent free form is a dimer [Ni(ONO)]₂, and represents one of the few examples of dinuclear nickel complexes with a planar [NO₃] coordination. The phenolic O-atoms act as bridging ligands. Due to their reduced π-donor strength the bond lengths Ni? O trans to the bridges are significantly shortened. In contrast to the analogous complex with an aliphatic bridge, “NiEIA”, both halves of the dimeric molecules are coplanar with a Ni? Ni distance of 3.29 Å.     

Nickel(I)‐Komplexe mit 1,1′‐Bis(phosphino)ferrocenen als Liganden

Nickel(I) Complexes with 1,1′‐Bis(phosphino)ferrocenes as Ligands The thermically stable monomeric Nickel(I) complexes [(d^tbpf)Ni(acac)] ( 1 ) and [(dⁱppf)NiCl] ( 2 ) were synthesized and characterized by elemental analyses, EPR spectroscopy, and by X‐ray crystal structure analyses of single crystals (d^tbpf: 1,1′‐bis(di‐tertbutylphosphino)ferrocene; dⁱppf: 1,1′‐bis(diisopropylphosphino)ferrocene). 1 is formed by reduction of Ni(acac)₂ with triethylaluminium in the presence of d^tbpf, together with the nickel(0) complex [(d^tbpf)Ni(C₂H₄)]. 1 contains a Ni^I atom surrounded of two O‐ and two P donor atoms in a distorted tetrahedral coordination. 2 was obtained by reduction of [(dⁱppf)NiCl₂] with NaBH₄. In 2 the nickel(I) atom adopts trigonal planar coordination.     

Nickel complexes with cyclic ligands containing P and N atoms as coordination sites: novel biomimetic catalysts for hydrogen oxidation

Nickel complexes with new cyclic ligands containing phosphorus and nitrogen atoms as coordination sites are novel efficient catalysts for hydrogen oxidation. A systematic study of their electrochemical properties made it possible to classify the nickel systems in question into four groups according to the sequence of electron transfer processes in the reduction (M^II-M^I-M⁰) and to the nature of solvents and counterions. Regularities of catalytic transformations involving nickel complexes with P,N-cyclic ligands in the H₂ oxidation reaction in the coordination sphere of the catalyst and a correlation between the structure of the complex and its redox properties were established. The most efficient catalysts contain phenyl and 2-pyridyl substituents at the phosphorus atom and benzyl or 2-pyridyl substituents at the nitrogen atom.     

Koordinationsverbindungen des 2-Hydroxy-4,6-diphenyl-thiobenzophenons. Chelat-Komplexe des Cobalts und Nickels,Röntgenkristallstrukturanalyse der Nickelverbindung

Coordination Compounds of 2-Hydroxy-4,6-diphenyl-thiobenzophenone. Chelate Complexes of Cobalt and Nickel, X-ray Structure of the Nickel Compound 2-Hydroxy-4,6-diphenyl-thiobenzophenone (HL) reacts under deprotonation with metal salts to chelate complexes. The reactions with nickel acetate or cobalt acetate yield neutral complexes of the composition NiL₂ and CoL₃, respectively. The nickel compound crystallizes monoclinic in the space group P2₁/c (No. 14), a = 17.55(6), b = 26.69(4), c = 8.49(9) Å, β = 102.7(2)°, Z = 4. The nickel atom has a distorted squareplanar coordination sphere. The ligands are cis coordinated.     

Oxydation von Nickel(0)-Komplexen mit cyclischen Carbonsäureamiden

Oxidation of Nickel(0) Complexes by Cyclic Imides of Dicarbonic Acids Normally, phthalimide (PI? H) or succinimide (SI? H) react with nickel(0) complexes — (dipy)Ni(COD) or (Ph₃P)₂Ni(C₂H₄) — by oxidative addition. The reaction of PI? H and the strong reductant (dipy)Ni(COD) is initiated by a one-electron transfer. Depending on the solvent, the resulting ion pair affords (dipy)Ni^I(PI) by spontaneous fragmentation or (dipy)Ni^II(H)(PI) by cage collaps. No interaction is found between the weak reductant (Ph₃P)Ni(C₂H₄) and PI? H. Phosphine-containing nickel(0) complexes are electrophilically attacked by the acid NH group of SI? H. Hydrido complexes of nickel(0), such as (Cy₃P)₂Ni(H)(SI), or secondary products of them, such as [(SI)Ni(THF)]₂NH, are formed. On the other hand, the reaction with (dipy)Ni(COD) affords only the binuclear substitution product [(dipy)Ni]₂(SI? H)(THF). In solution prolongated heating of (dipy)Ni(PI)(THF)_0,5 results in a partial decarbonylation. In contrast to the reaction of (dipy)Ni(COD) and cyclic carbonic acid anhydrides, no definite metalla rings but by an interaction with the solvent, benzamide is formed. With (dipy)Ni(COD) maleinimide does not react like on NH-acidic compound but like a polar olefine by substitution.     

Nickel(0)-induzierte CC-verknüpfung zwischen 1,2-dienen und kohlendioxid

1,2-Dienes react with CO₂ at nickel(O) under the influence of basic chelate ligands to form nickela carboxylates. The structures of these five-membered complexes have been determined by spectroscopic and chemical methods. The regioselectivity of the CC bond formation is discussed.     

Wechselwirkungen zwischen Hetero-π-Systemen und Zentralmetallen niedriger Oxydationsstufen: Stöchiometrische Verknüpfungsreaktionen von Azomethinen und 1,3-Dienen am Nickel(0)

Interactions between Hetero-π-Systems and Central Metals in Low Oxidation States: Stoichiometric Reactions of Azomethines and 1,3-Dienes with Nickel(0) Azomethines and 1,3-Dienes react with Ni(COD)₂ under oxydative coupling to form different types of organo nickel(II) compounds. The route of this reactions depends on the nature of the azomethines and dienes and can be controlled by kinetic and thermodynamic parameters. The new complexes are investigated by IR, MS, and H-NMR measurements. The reaction of cinnamaldehydanil and dienes with Ni(COD)₂ gives a binuclear complex. X-ray analysis shows that 2 C₇N-chains are bonded to 2 Nickel(II) central atoms.     

Bis(diphenylphosphano)alkan- und 1-(Diphenylphosphano)-2-(2-pyridino)ethan-N-Arylsulfinylamin-Nickel(0)-Komplexe

Bis(diphenylphosphano)alkane- and 1-Diphenylphosphano-2-(2-pyridino)ethane-N-arylsulfinylamine Nickel(0) Complexes Synthesis and properties of the bis(diphenylphosphano)alkane-N-phenyl-sulfinylamine-nickel(0) complexes [Ni{Ph₂P(CH₂)_nPPh₂}(PhNSO)] (n = 2 dppe, n = 3 dppp, n = 4 dppb) as well as of the 1-(diphenylphosphano)-2-(2-pyridino)ethane nickel(0) complexes [Ni(dpppe)₂], [Ni(dpppe)(p-TolNSO)] and [Ni(dpppe)(PPh₃)₂] are described. These compounds have been characterized by i. r. and ³¹P n.m.r. spectroscopy. The N-arylsulfinylamine ligands are η²-(N, S)-side on coordinated.     

Nickel(II) chloride complexes of 1,5-disubstituted 2,4-dithiobiurets

The complex compounds formed by the interaction of Nickel(II) chloride with 1,5-disubstituted 2,4-dithiobiurets, have been isolated and characterised. The structure of these complexes have been studied by i.r. spectra, conductance and magnetic susceptibility measurements. It has been found that coordination occurs in these ligands through thiocarbonyl sulphur atoms, present in ligand molecule, which is supported by the potentiometric titrations of ligands and complexes with iodine in THF.     

Reactions of 2,4-pentadienoic acid methyl ester with nickel(0) and platinum(0) compounds

The course of the reaction of the title compound with nickel(0) and platinum(0) complexes strongly depends on the kind and number of the additional ligands attached to the metal, and a variety of metal complexes can be formed.     

Complexation Kinetics of N‐Alkyl‐Substituted Diamino Diamides with Nickel (II) in Aqueous Solution

Equilibrium constants are deter mined for the protonation and metal complexation of the nickel(II) complexes with 4‐methyl‐4,7‐diazadecanediamide (4‐Me‐L‐2,2,2), 4,7‐dimethyl‐4,7‐diazadecanediamide (4,7‐N,N′‐Me₂‐L‐2,2,2), 4‐ethyl‐4,7‐diazadecanediamide (4‐Et‐L‐2,2,2), and 4‐methyl‐4,8‐ diazaundecane diamide (4‐Me‐L‐2,3,2), in 0.10 M KCl at 25.0°C. The formation kinetics of these nickel (II) complexes have been studied under the same conditions with use of the stopped‐flow technique. The possible path ways for the complexation reaction of nickel (II) with these ligands are discussed. The first metal‐nitrogen bond formation is proposed as the rate‐determining step for the reactions of nickel (II) with the unprotonated ligands; proton loss is the rate‐limiting step in the reactions of nickel (II) with the monoprotonated ligands. Similarly, in dissociation reactions of these nickel (II) complexes, the rate‐determining step for the water dissociation pathway is the break age of the second nickel‐nitrogen bond; the rate‐determining step for the proton‐assisted path way is the protonation of the released amino group. The important factors determining the reactivity of these complexes are considered. The kinetic results of the formation and dissociation reactions of these complexes are consistent with dissociative mechanism.