Nickel complexes amine oxides

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... 

Few studies have systematically examined how chemical characteristics of organic reductants influence rates of reductive dissolution. Oxidation of aliphatic alcohols and amines by iron, cobalt, and nickel oxide-coated electrodes was examined by Fleischman et al. (38). Experiments revealed that reductant molecules adsorb to the oxide surface, and that electron transfer within the surface complex is the rate-limiting step. It was also found that (i) amines are oxidized more quickly than corresponding alcohols, (ii) primary alcohols and amines are oxidized more quickly than secondary and tertiary analogs, and (iii) increased chain length and branching inhibit the reaction (38). The three different transition metal oxide surfaces exhibited different behavior as well. Rates of amine oxidation by the oxides considered decreased in the order Ni > Co >... 

The starting material is an 18 electron nickel zero complex which is protonated forming a divalent nickel hydride. This can react further with alkenes to give alkyl groups, but it also reacts as an acid with hard bases to regenerate the nickel zero complex. Similar oxidative addition reactions have been recorded for phenols, water, amines, carboxylic acids, mineral acids (HCN), etc. 

Two other refining processes are also frequently employed. One involves hydrometallurgical refining in which sulfide concentrates are leached with ammonia solution to convert the copper, nickel, and cobalt sulfides into their complex amines. Copper is precipitated from this solution upon heating. Under such conditions, the sulfide-amine mixture of nickel and cobalt are oxidized to their sulfates. The sulfates then are reduced to metalhc nickel and cobalt by heating with hydrogen at elevated temperatures under pressure. The metals are obtained in their powder form. 

Tetra- and penta-peptide complexes of Ni(II) have been shown to consume O2 in neutral solutions as the metal ion catalyzes the oxidation of the peptide to give a number of products including amides of amino acids and of peptides, 0x0 acids and CO2 [167]. A nickel cyclic amine complex has been shown to react with dioxygen [168] to give a 1 1 complex. When excess oxygen was added, attack on the ligand system occurred. 

Treatment of the amino-phosphine complex with H2 generates a hydrido nickel complex with a pendant ammonium substituent. Catalysis, which was established electrochemicaUy, is proposed to involve oxidation of the Ni(ll) hydride to a Ni(III) hydride, a process which enhances the acidity of the hydrido ligand sufficiently to allow its deprotonation by the pendant amine (Fig. 12.12). This proton transfer gives an easily oxidized Ni(I) intermediate. Catalysis of the H2 oxidation by mononuclear nickel complexes foreshadows the preparation of related bimetallic species exhibiting hydrogenase reactivity. 

A review has appeared on the synthesis and reactivity of (sUylamino) and (silyl-anilino)phosphines. The S5mthesis, derivatisation and coordination behaviour of the morpholine (69) and piperazine (70) derivatives have been described. They are formed from the appropriate amine with diphenylchlorophosphine, and both react with sulfur or selenium to give the chalcogenide, whilst reaction of (69) with paraformaldehyde leads to insertion of methylene into the P N bond to give the phosphine oxide. The reaction between ethylenediamine and diphenylchlorophosphine can lead to the bis-, tris- and tetrakis(diphenylphosphino)ethylene-diamines, depending upon the stoichiometry. The first two are oxidised in situ whist the latter, (71), is stable. A nickel complex of (71) has been shown to be active as a catalyst for ethylene pol5nnerisation. ... 

I, Table X) requires tertiary phosphine-nickel halide or tertiary phosphine-nickel carbonyl complexes at 140-170°C. This implies oxidative addition of aromatic halides to nickel, replacement of the halide with amines, and reductive elimination. 

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- ... 

Consequently, by choosing proper conditions, especially the ratios of the carbonyl compound to the amino compound, very good yields of the desired amines can be obtained [322, 953]. In catalytic hydrogenations alkylation of amines was also achieved by alcohols under the conditions when they may be dehydrogenated to the carbonyl compounds [803]. The reaction of aldehydes and ketones with ammonia and amines in the presence of hydrogen is carried out on catalysts platinum oxide [957], nickel [803, 958] or Raney nickel [956, 959,960]. Yields range from low (23-35%) to very high (93%). An alternative route is the use of complex borohydrides sodium borohydride [954], lithium cyanoborohydride [955] and sodium cyanoborohydride [103] in aqueous-alcoholic solutions of pH 5-8. 

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