2,2 -Bipyridyl nickel

New complexes have been prepared by the thermal decomposition of tris(2,2 -bipyridyl)nickel(II) and cobalt(II) chlorides, i.e., M(bipy).2Cl2,... 

Dichlorobis( 2,2 -bipyridyl )nickel(II) jlead( II) bromide j aluminium <-... 

E,E)-l,4-Diaryl-l,3-dienes. A mixture of p-bromostyrene, catalytic amounts of dichlorobis(2,2 -bipyridyl)nickel(II) and PbBr2,. 7 and Al in methanol stirred at room temp, for 6 h under argon 1,4-diphenyl-1,3-butadiene. Y 83% (E,E/E,Z 97 3). KI is not essential, but quickens the process BiCl3 is effective in place of PbBr2. F.e. and conversion to terphenyls via diene synthesis s. H. Tanaka et al.. Tetrahedron Letters 30, 26 -A (1989). 

C30H2ftNgNiOiiS 7.5 H2O, Tris-(2,2 -bipyridyl)nickel(ll) sulfate hydrate, 42B, 865... 

Bis(bipyridyl)nickel(0) has been prepared by metal-vapor methods and electrochemical data were obtained for it. In these low-valence states, a significant proportion of the electron density lies on the bipy ligand.2469 Also, the crystal and molecular structure of 4,6-dimethyl-2,2 -dipyr-idyldicarbonylnickel(O) (1021) has been determined. The coordination geometry about Ni is tetrahedral.2470... 

Recently, Kumada et al. (49) have published a report on what they refer to as dehydrogenative, stereoselective cis double silylation of internal acetylenes. This appears to be a variation of Eq. (53), with diethyl bipyridyl nickel(11) as the catalyst, in which hydrogen is liberated instead of being added to an alkene to form a saturated product. 

The air-sensitive violet complex thus formed was treated with methyl-magnesium bromide and then hydrolyzed to give /rans-Ph(Me3Si)C= CPh(SiMe3) (90, 91). Apparently, this is the first example of transfer of silyl groups from a metal to a coordinated hydrocarbon ligand. It seems that a similar step is involved in the dehydrogenative cis double silylation of acetylenes catalyzed by diethyl(bipyridyl)nickel(II) (156). 

With diethyl(bipyridyl)nickel(II) and chlorohydrosilanes, the hydrosilyiation of di-substituted acetylenes undergoes dehydrogenative, stereoselective c -double silylation to give 1,2-bissilylalkenes, accompanied by normal hydrosilylated products ... 

The arylation reaction of primary and secondary amines has been investigated using nickel or palladium complexes as catalysts, and bromo- or chloroarenes as arylating agents. Among the complexes tested, the more efficient catalyst is the bis (bipyridyl) nickel (II) bromide, bipy2NiBr2, which affords for example high yields in the arylation of allylamine with /n-bromotrifluoromethylbenzene. The reduction of the haloarene, sometimes observed with the nickel complexes, becomes predominant with palladium catalysts whatever the complex used. 

Dialkyl(bipyridyl)nickel(II) forms unstable olefin addition complexes NiR2-(bipy)(ol) with acrylonitrile and acrolein . The stability of the product depends on the alkyl group present in the order R = Et > n-Pr > i-Bu > Me " . 

Little C—Se bond formation by palladium catalysis has been reported, although these reactions should be feasible considering the ability of palladium complexes to catalyze C—S, C—P, and C—As bond formation. However, nickel complexes have been used for carbon-selenium bond formation. In 1985, Cristau and co-workers used bis(bipyridyl)nickel(ll) bromide to form aryl selenides from aryl halides and sodium benzeneselenoate. ... 

Henne BJ, Bartak DE (1984) Metal-vapor synthesis and electroeherrristry of bis(bipyridyl) nickel(O). Inorg Chem 23 369-373... 

Diethyl(bipyridyl)nickel(II) activated as a catalyst for propylene dimerization by the addition of a Lewis acid such as EtAlCh or EtiAlCl with an Al/Ni... 

In 1956 it was found that when pyridine is refluxed with a modified Raney-nickel catalyst, 2,2 -bipyridine (1) is formed in satisfactory yield. The isomeric bipyridines could not be detected, and the product was readily purified. Similar heterocyclic biaryls have been formed in the same way from substituted pyridines and from some related compounds, the yield being dependent on the nature of the compound. The reaction has become the method of choice for the preparation of 2,2 -bipyridine, and it is now used on an industrial scale. Bipyridyls are of particular importance as chelating agents. 

Combination of nickel bromide (or nickel acetylacetonate) and A. A -dibutylnorephcdrinc catalyzed the enantioselective conjugate addition of dialkylzincs to a./Tunsaturated ketones to afford optically active //-substituted ketones in up to ca. 50% ee53. Use of the nickel(II) bipyridyl-chiral ligand complex in acetonitrile/toluenc as an in situ prepared catalyst system afforded the //-substituted ketones 2, from aryl-substituted enones 1, in up to 90% ee54. 

The majority of the work on xanthates of divalent nickel has, in recent years, been centered on the formation of base adducts with [Ni(Rxant)2]. Carlin and Siegel (348) and Daktenieks and Graddon (349) reported the formation of paramagnetic [Ni(Etxant)2B2] or [Ni(Etaxant)2B], where B = pyridine, 4-methylpyridine, bipyridyl, or... 

The bipyridyl ligand, with 80 %, gives the best catalyst, probably because it affords the best balance between the a-donor and rt-acceptor characters which favours respectively the oxidative addition of the aryl bromide and the reductive elimination of the aryl ether at the nickel center. 

Dibenzofuran is also formed when phenoxathiin is desulfurized by bis( 1,5-cyclooctadiene)nickel(O) and 2,2 -bipyridyl, but limited synthetic application can be envisaged for this type of reaction despite the high yield obtained (see Scheme 77).140... 

Into a Schlenk tube was placed Auf 1,5-cyclooctadiene)-nickeI(0) (2.6 mmol), 2,2 -bipyridyl (2.6mmol), 1,5-cyclooctadiene (0.2ml), DMF (4ml), and toluene (8 ml). The reaction mixture was heated to 80°C for 0.5 h under argon. The dibromide comonomers 623 and 634 dissolved in degassed toluene (8 ml molar ratio of dibromides to nickel complex 0.65) were added under argon to the DMF-toluene solution and the polymerization maintained at 80°C for 3 days in the dark. 2-Bromofluorene (molar ratio of dibromides to monobromide 0.1) dissolved in degassed toluene (1ml) was added and the reaction continued for 12 h. The polymers were precipitated by addition of the hot solution dropwise to an equivolume mixture of concentrated HC1, methanol, and acetone. The isolated polymers were then dissolved in toluene or dichlor-omethane and reprecipitated with methanol/acetone (1 1). The copolymers were dried at 80°C in vacuo. The isolated yields of copolymers 240a-c were 79-85%. 

Desulfuration.1 This complex as such or in combination with 2,2 -bipyridyl (bpy) or triphenylphosphine (a NiCRAL) can effect desulfuration of heteroarenes. aryl thioethers, dithioketals, sulfoxides, or sulfones in DME or THF at 63° in 1.5-30 hours. NiCRA is sufficient for aryl thioethers, dithioketals, but NiCRALs are more efficient for desulfuration of heteroarenes. Yields can be comparable with those obtained with Raney nickel. 

Tetramethyl- or tetraphenyl- (cyclobutadiene)nickel dihalides undergo reductive ligand substitution with nitrogen donor ligands such as 2,2 -bipyridine or 1,4-diaza-1,3-dienes with the addition of sodium metal237. The 2,2/-bipyridyl ligand is readily displaced and reaction of this complex with a variety of olefins and alkynes leads to cycloaddition reactions with the cyclobutadiene ligand. 

Reductive dimerization of substituted pyridines to yield bipyridyls by zinc is catalysed by nickel salts under phase-transfer catalytic conditions [25]. 

The formation of arylzinc reagents can also be accomplished by using electrochemical methods. With a sacrificial zinc anode and in the presence of nickel 2,2-bipyridyl, polyfunctional zinc reagents of type 36 can be prepared in excellent yields (Scheme 14) . An electrochemical conversion of aryl halides to arylzinc compounds can also be achieved by a cobalt catalysis in DMF/pyridine mixture . The mechanism of this reaction has been carefully studied . This method can also be applied to heterocyclic compounds such as 2- or 3-chloropyridine and 2- or 3-bromothiophenes . Zinc can also be elec-trochemically activated and a mixture of zinc metal and small amounts of zinc formed by electroreduction of zinc halides are very reactive toward a-bromoesters and allylic or benzylic bromides . ... 

A reactor was charged with the step 4 product (0.96 g), 2,2 -bipyridyl (0.55 g), and THF (80 g). After deaeration, bis(l,5-cyclooctadiene)nickel(0) (1.05 g) was added and the mixture heated to 60°C for 1.5 hours and then cooled and precipitated in 300 ml of ion exchange water. The precipitate was isolated and then dissolved in chloroform, filtered, and purified by passing through a column filled with alumina. The polymer was reprecipitated in methanol, reisolated, dried, and 0.5 g of product isolated having an Mn of 7.3 x 10s Da. 

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