Nickel complexes imidazole

Thiazole, C3H3NS, and substituted thiazoles coordinate through the nitrogen atom in nickel complexes as imidazole does.901-903... 

A number of nickel complexes with substituted and unsubstituted tetrazoles910-913 and with pyrazole- and imidazole-derived ligands have also been reported recently.914-916... 

The equilibria in the nickel(II)-imidazole-chloride ternary system have been investigated by means of pH-metric and spectrophotometric titrations in 3 M Na(C104, Cl) solution. The latter method was used to determine the stability constant of the binary NiCr complex in the nickel(II)-chloride system. The concentration range studied was [NP" ] = 0.096 to 0.300 M and [Cl ] = 1.25 to 3.00 M. The log, yff value obtained (- (0.47 0.10)) is in good agreement with that determined from potentiometric data in... 

Dam J, Hakvoort G, Jansen J, Reedijk J. 1975. Thermochemistry of nickel(II) imidazole complexes. J InorgNud Chem 57 713-718. 

Reaction of l,3-bis(phenylmethyl)imidazol-2-ylidene with nickel tetra carbonyl gives [(t (C)-1,3-bis(phenylmethyl)imidazol-2-ylidene)Ni(CO)3] (970M2472). Complexes of composition [Ni(CO)2L2] with imidazol-2-ylidenes are also known (93JOM(459)177). Another species to be mentioned in this respect is bis(l,3-dimesitylimidazol-2-ylidene)nickel(0) (94JA4391). 1,3-Dicyclohexylimidazol-2-yUdene substitutes triphenylphosphine or THF from [NiX LJ (X = Cl, Br L PPhj, THF) to yield the stable nickel(II) complexes 69 (X = C1, Br R = Cy) (97OM2209). Another preparation of nickel(II) derivatives is the interaction of... 

Co-condensation reaction of the vapors of l,3-di-rcrt-butylimidazol-2-ylidene and nickel, palladium, or platinum gives the coordinatively unsaturated 14-electron sandwiches [L M] (M=Ni, Pd, Pt) of the carbene type (990M3228). Palladium(O) carbene complexes can also be prepared by the direct interaction of l,3-R2-imidazol-2-ylidenes (R=/-Pr, r-Bu, Cy, Mes) (L) with the palladium(O) compound [Pd(P(o-Tol)3)2] (OOJOM(595)186), and the product at the first stage is [(L)PdP(o-Tol)3l, and then in excess free carbene [PdL ]. 

Reduction of both nickel porphyrins and thiaporphyrins to Ni1 species has been studied by EPR and 2H NMR spectroscopy.179, 2 58 The Ni1 complex of 5,10,15,20-tetraphenyl-21-thiaporphyrin has been isolated and characterized. Reaction of this complex with sulfur dioxide produced a paramagnetic five-coordinated Ni1 S02 adduct, while reaction with nitrogenous base ligands (amines, pyridines, imidazoles) yielded five- and six-coordinate complexes. In addition, the crystal structure of Ni1 diphenyldi-p-tolyl-21-thiaporphyrin has been determined. The coordination geometry about the nickel center is essentially square planar with extremely short Ni—N and Ni—S bonds (Ni—N = 2.015(2) A, 2.014(12) A, and 1.910(14) A and Ni—S = 2.143(6) A).2359... 

Nickel(III) peptide complexes have a tetragonally-distorted octahedral geometry as shown by electron spin resonance studies (19) and by reaction entropies for the Ni(III,II) redox couple (17). Axial substitutions for Ni(III)-peptide complexes are very fast with formation rate constants for imidazole greater... 

A variation of the thermal elimination of an alcohol from the neutral 2-alkoxy-1,2-dihydro-l//-imidazole is the preformation of a chelate vic-bisamine complex which is subsequently attacked by an ort/io-ester to form the desired NHC complex. This principle has been shown with nickel and platinum [Eq. 

Ni" forms square-planar bis-complexes with the amidate anions of L-Val, L-Phe, and L-Pro. The structure of bis(Gly)-bis(imidazole)nickel(ii) has been reported and the configuration around the metal atom is cis-O(carboxyl), cis-N(amine), cis-N(imidazole). Tetra- and penta-peptide complexes of nickel(ii) consume oxygen in neutral solutions as the metal ion catalyses peptide oxidation to give a number of products, including amides of amino-acids and peptides, oxo-acids, and C02- ... 

Selected nickel(II) complexes with imidazole, pyrazole and related ligands are shown in Table 48. 

Hexakis imidazole and pyrazole complexes of nickel(II) can be easily obtained by the direct reaction of the hydrated nickel(II) salt with the appropriate ligand using ethanol as solvent and stoichiometric amounts of the reactants.898 899 Analogous complexes can be obtained with pyrazoles and imidazoles having substituents in positions not adjacent to the donor site. 

The effects of the substituents near the donor site is to reduce the number of coordinated ligand molecules from six to four or less. Tetrakis complexes with substituted pyrazoles and imidazoles are prepared using a large excess of the ligands, and, in the cases of 1,2-dimethylimidazole and 3,5-dimethylpyrazole derivatives, anhydrous reactants. Most of die mono and bis adducts may be conveniently prepared under anhydrous conditions and with the nickel salt in excess. 

The neutral complexes Ni(C3H3N2)2 are obtained by the reaction of hydrated nickel(II) chloride and pyrazole, or imidazole, in an aqueous ammonia solution. These insoluble complexes contain uninegative exobidentate pyrazolates or imidazolates which act as bridges between two metals (104).899,904,905 Two additional ligands such as NH3, H20 or py may be... 

In the chain polynuclear complex Ni(04C4)(Im)2(H20)2 (Im = imidazole) only two oxygen atoms of the bridging squarate are directly coordinated to nickel(II).1788... 

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