Ethanol, nickel complexes

The nickel complexes with 2-aminopyridines bear some similarity to complexes of the corresponding aliphatic diamines (Section 50.5.3.2). Most of the complexes are easily obtained by the direct reaction of nickel(II) salts with the appropriate amount of the diamine in ethanol solution. Complexes with JV-substituted aminopyridines are preferably synthesized under anhydrous conditions. 

A series of complexes of 2-carbonyl derivatives of 3-hydroxybenzo[b]thiophene 679, its imines 680 (R/ = Ph) [250] and hydrazones 680 (R = NR2R3) [251], as well as pyperidine adduct of nickel complex 681 [252], have been isolated in methanol-ethanol mixture ... 

Powdered sodium tetrahydroborate(l -) (0.37 g, 0.01 mol) is added in three portions at about 30-min intervals to a suspension of dichlorobis(tri-isopropylphosphine)nickel (4.5 g, 0.01 mol) in diethyl ether (300 mL) and 95% ethanol (50 mL) in a 500-mL three-necked flask with an argon inlet and a gas bubbler vented to the hood. The reaction mixture is stirred with a magnetic stirring bar at 20° for approximately 5 hr. Gas evolution is observed, and the nickel complex dissolves gradually. After all the nickel compound is dissolved, the solution is filtered into a 500-mL two-necked flask and the solvent is removed under reduced pressure. The yellow residue is extracted with petroleum ether (200 mL), and the solution is washed with two 50-mL portions of water. The petroleum layer is separated, dried with 15 g of anhydrous sodium sulfate, which is washed with two 10-mL portions of the solvent which are added to the petroleum extract the combined extract is then filtered and concentrated in vacuo. The saturated solution (approximately 100 mL) is cooled to —78° in a Dry lce-2-propanol mixture overnight. The crystals which are formed are filtered, washed with a small amount (approximately 10 mL) of petroleum ether at 0°, and dried in vacuo to give brown crystals, mp 65-66° (decomposes). (Yield 2.5 g, 60%.) Anal. Calcd. for Cl8H43ClNiP2 C, 52.1 H, 10.4 Ni, 14.1. Found C, 52.3 H, 9.7 Ni, 14.1. 

The procedure described in Sec. D for the preparation of dibromotetrakis(ethanol)nickel(II) is followed. The anhydrous ethanol solution is evaporated to the stage of incipient crystallization at the boiling point and then diluted with 1 1. of peroxide-free anhydrous 1,2-dimethoxyethane. The resulting salmon-pink complex is collected under nitrogen in a Schlenk frit of 1-1. capacity, rinsed successively with anhydrous 1,2-dimethoxyethane and then pentane and dried in a current of nitrogen at 23° and 20 cm. Hg. The yield is nearly quantitative. f Anal. Calcd. for C4H10Br2O2Ni C, 15.57 H, 3.27 Br, 51.78 Ni, 19.02. Found C, 15.01 H, 3.43 Br, 52.15 Ni, 18.80. 

The nickel complex salt 23 readily underwent ligand exchange with various tridentate ligands.For example, addition of an equimolar amount of tris[2-(diphenylphosphanyl)-ethyljphosphane to 23 in dichloromethane, followed by addition of sodium tetraphenylborate in ethanol, gave the complex salt 24, whose structure was determined by X-ray crystallography. ... 

Ethanol Imine Ligands and their Nickel Complexes... 

Potassium hexacyanodinickelate(I) is a bright red compound which reacts slowly in air to form a yellow solid. It is insoluble in ethanol and liquid ammonia but dissolves readily in water, giving a blood-red solution with strong reducing properties. In the presence of excess cyanide ion the unipositive nickel is rapidly oxidized by water to the dipositive condition. It has been reported1 that acidification of aqueous solutions of the complex results in the precipitation of nickel(I) cyanide and that the latter dissolves in aqueous potassium cyanide with the formation of the original complex. Solutions of the unipositive nickel complex rapidly absorb carbon monoxide... 

Stable nickel complexes can be isolated by chromatographic methods from the hydrogenation of 3,5-dichloro-jV,jV-diisopropyl-l24,2,4,6-thiatriazin-1-arnine. The hydrogenolysis in water gives the nickel complex of an aldimino formamidine, whereas in ethanol the nickel complex of bis(/V2-imidoylcarboximidic) acid ester is formed.45... 

For example, [Ni(PEt3)4] can be protonated with weak acids such as ethanol. An intermediate basicity is obtained with triarylphosphines and -phosphites, and protonation of the corresponding nickel complexes requires strong mineral acids. In contrast, PF3 complexes exhibit negligible basicity because PF3 is a strong electron acceptor, like CO. 

The selective displacement of bromine fromo-bromochlorobenzene(fccABr = 0.0030) by a soft Ni(0) complex (25) has been demonstrated. In refluxing ethanol, nickel tetracarbonyl reacts with aryl iodides to give aroic esters (26). As aryl bromides and alkyl halides are inert, the softness of the acceptor is thus of great importance. 

On boiling L262 and Ni(CH3C00)2-4H20 (molar ratio 2 1) in aqueous ethanol, [Ni(L263)j and the nickel complex of 2-methylbenzimidazole are formed [312]. 

When dap reacts with an aromatic 3,3-triamine in the presence of nickel(II), copper(II) or cobalt(II) perchlorate in ethanol, macrocyclic complexes with tetra-dentate ligands [M(L712)](C104)2 and having octahedral structures are isolated (Eq. 3.35) [73]. 

Y-Ray analysis has revealed the structure of an intermediate (366) in the oligomerization of allene by nickel complexes which contains three allene units and is assumed to be formed by the series of steps in Scheme Using rhodium dicarbonyl chloride dimer and triphenylphosphine in ethanol, an allene hexamer has been isolated for which structure (367) is proposed. 2... 

Stability constants for palladium complexes, [Pd(S2CNR2)2] (R = Me, Et, Pr, /-Pr), have been measured in ethanol using UV-vis spectroscopy (393). Their stability varies in the order i-Pr > Pr > Et > Me being the same as that found for the analogous nickel complexes. Further, a comparison with related nickel and cobalt complexes showed the palladium complexes to be the most stable Pd > Ni > Co (393). 

Cyclopentadiene itself has been used as a feedstock for carbon fiber manufacture (76). Cyclopentadiene is also a component of supported metallocene—alumoxane polymerization catalysts in the preparation of syndiotactic polyolefins (77), as a nickel or iron complex in the production of methanol and ethanol from synthesis gas (78), and as Group VIII metal complexes for the production of acetaldehyde from methanol and synthesis gas (79). 

Snyder and Smith prepared diethyl acetamidomalonate in 40% yield by reduction of diethyl isonitrosomalonate in ethanol over palladium on charcoal followed by direct acetylation of diethyl aminomalonate in the filtrate with acetic anhydride. Ghosh and Dutta used zinc dust instead of palladium. A modification using Raney nickel is described by Akabori et al. Shaw and Nolan reported a 98% yield by conversion of diethyl oximino-malonate-sodium acetate complex. 

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