2 -Bipyridine, nickel complex

NjCeHij, 1,2-Ethanediamine, N,NJi, N -tetramethyl-, lithium complex, 26 148 NjCioHg, 2,2 -Bipyridine, nickel complex, 28 103... 

Katayama Y, Toshimitsu Y, Miura T (2014) Electrode kinetics of the redox reaction of tris (2,2 -bipyridine)nickel complexes in an ionic liquid. Electrochim Acta 131 36-41... 

Alkylnickel amido complexes ligated by bipyridine have been prepared that undergo reductive elimination of V-alkyl amines (Equation (54)).207,208 Unlike the phosphine-ligated palladium arylamides, these complexes underwent reductive elimination only after oxidation to nickel(III). Thermally induced reductive elimination of alkylamines from phosphine-ligated nickel complexes appears to occur after consumption of phosphine by arylazides 209... 

Biaryl synthesis from aryl halides is a more interesting reaction due to the value of these molecules and their difficult access by chemical methods. The first electrosyntheses were simultaneously done in 1979-80 by three groups [21-23] who used NiCljPPha (1-20%) as catalyst precursor in the presence of excess PPhs. Later, several groups investigated the use of bidentate phosphines like dppe associated with nickel in the synthesis of various biaryls, and notably 2,2 -bipyridine and of 2,2 -biquinoline from respectively 2-chloropyridine and 2-chloroquinoline [24], More recently new nickel complexes with l,2-bis(di-2-alkyl-phosphino)benzene have been studied from both fundamental and synthetic points of view [25]. They have been applied to the coupling of aryl halides. 

The bi-electronic reduction of this nickel compound generates a zero-valent nickel complex which is stable on the time scale of cyclic voltametry, provided at least three bipyridine ligands per nickel center are present. 

The electrochemical preparation of organozinc compounds obtained from the corresponding aromatic halides and with the use of a nickel complex as catalyst is only efficient in dimethylformamide as solvent. Moreover, in most cases and as described previously, the reaction requires the presence of excess 2,2 -bipyridine (five molar equivalents with respect to nickel) to achieve the transmetallation reaction leading to the organozinc compound and to avoid the formation of biaryl, Ar-Ar (equation 53). 

However most organic halides are less easily reduced than Zn(II). So such a process can only be applied if one is able to catalyse the electroreduction of RX. This can be achieved by electrochemically formed zerovalent nickel complexes. Thus Ni(II)-2,2 -bipyridine (Ni-bpy) compounds can catalyse the electroreduction of alkyl and aryl halides1 at potential more positive than... 

An electrocatalytic method for reductive N-O bond cleavage of 3-methoxyisoxazolines in the presence of nickel(O)-bipyridine [Ni(0)bpy] complex has been studied. The nickel complex, generated m situ from Ni(n)bpy, acts as the actual electron source. Under these conditions, isoxazoline 133 afforded a mixture of /3-hydroxyester 134 and /3-hydroxynitrile 135 in different ratios, depending on the amount of Ni(ll)bpy used, and in high overall yields (Scheme 29) <2003TL8217>. 

Synthetic applications of electrochemical reduction of allyl ethers in the presence of nickel complexes with bipyridines and tetraazamacrocycles as ligands 00CCC844. 

NjCsoHsj, 3,11,15,192226-Hexaazatricy-clo( 11.7.7. F loctacosa-1,5,7,9(28), 12,14,19,212 nonaene, 3,11-dibenzyl-1420-dimethyl-2,12-diphenyl-, iron complex, 27 280 nickel complex, 27 277 N8Cl20jRuC3 H3j 6H20, Ruthenium(II), tris(2,2 -bipyridine)-, dichloride, hexa-hydrate, 28 338... 

For example, the acyl-aryloxo bond cleavage (type b) is shown by the reaction of Ni(cod)2 with phenyl propionate in the presence of PPhs (Scheme 3.34) or 2,2 -bipyridine [65]. The reaction products are ethylene, phenol, and (car-bonyl)nickel complex. Formation of these products is conveniently understood by initial oxidative addition of EtC(0)-0Ph followed by decarbonylation, )S-hydrogen elimination and reductive elimination, though (acyl)(aryloxo)nickel(II) intermediate is not isolated. However, such an intermediate is isolated by the selective insertion of CO into the (alkyl)(aryloxo)nickel (or palladium) complexes, which smoothly affords esters by reductive elimination promoted by electron deficient olehns. The results suggest that the oxidative addition involving C-0 bond cleavage is essentially reversible. 

Associative path (c) has been mainly observed for nickel(II) complexes [BOSS], This is because nickel(II) has a higher propensity to make five-coordinate species than palladium(II) and platinum(II). A steric condition is another important factor. Thus the reductive elimination from bipyridine-coordinated dialkyl-nickel complexes is known to be effectively accelerated by addition of n-acceptor olefins such as maleic anhydride and acrylonitrile to the systems (Scheme 9.8)... 

In conjunction with the aforementioned trapping experiment, several attempts were made to isolate a nickel complex such as 10 analogous to the PT complex 11 [114] or such as 12 similar to the Fe complex 13 [115] by using 1,5-cyclooctadiene, 2,2 -bipyridine, triethylphosphine, or triphenylphosphine as stabilizing ligands see Figure 7.3. 

A novel method for the synthesis of aryl at RT has been proposed by Vicic [65]. Inexpensive nickel-bipyridine (bis(cyclooctadiene)nickel(O) (Ni(COD)2) and 4,4 -dimethoxyl-2,2 -bipyridine (dmbpy)) complexes were found to be active for the ttifluoromethylthiolation of heteroaryl iodides at room temperature using the convenient [NMe4][SCF3] reagent (Scheme 32). 

The synthesis of polydiacetylenes with bipyridine metal complexes in their sidechains has been achieved by Lindsell and cowoikers (Scheme 17). Complexes of nickel, copper, ruthenimn, and molybdenum were synthesized and the nonlinear optical properties of the resulting polymers examined. 

The most important by-product formed in the reaction of pyridine with degassed Raney nickel is an organonickel complex which has been shown to be a complex of one molecule of 2,2 -bipyridine, two molecules of 2,2 -pyrrolylpyridine (17), and one nickel II ion. It is significant that, although the formation of 2,2 -bipyridine ceases after 50 hr refluxing, the formation of this complex continues for at least another 140 hr. 

The synthetic route represents a classical ladder polymer synthesis a suitably substituted, open-chain precursor polymer is cyclized to a band structure in a polymer-analogous fashion. The first step here, formation of the polymeric, open-chain precursor structure, is AA-type coupling of a 2,5-dibromo-1,4-dibenzoyl-benzene derivative, by a Yamamoto-type aryl-aryl coupling. The reagent employed for dehalogenation, the nickel(0)/l,5-cyclooctadiene complex (Ni(COD)2), was used in stoichiometric amounts with co-reagents (2,2 -bipyridine and 1,5-cyclooctadiene), in dimethylacetamide or dimethylformamide as solvent. 

In a series of studies of the spectroscopy and photochemistry of nickel(O) -a-diimine complexes, the structural differences among the complexes NiL2 and Ni(CO)2L (L Q-diimine) have been examined by means of molecular orbital calculations and electronic absorption Raman resonance studies.2471, 472 Summing up earlier work, the noninnocence of a-diimine ligands with a flat — N=C—C=N— skeleton in low-valent Ni chemistry and the course of substitution reactions of Ni° complexes with 1,4-diaza-1,3-dienes or a,a -bipyridine have been reviewed.2473... 

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