Nickel diamine complex

Curtis has discussed the preparation of complexes of this general class in a comprehensive review. Condensation of several nickel and copper diamine complexes with a range of aliphatic aldehydes and ketones has led to the synthesis of a wide variety of macrocycles containing varying substituents and/or varying macrocyclic ring sizes. " The mechanism of the general reaction is not understood. 

Shimazaki Y, Tani F, Fukui K et al (2003) One-electron oxidized nickel(II)-(disalicylidene) diamine complex temperature-dependent tautomerism between Ni(III)-phenolate and Ni(II)-phenoxyl radical states. J Am Chem Soc 125 10512-10513... 

Storr T, Wasinger EC, Pratt RC et al (2007) The geometric and electronic stmcture of a one-electron-oxidized nickel(II) bis(salicylidene)diamine complex. Angew Chem Int Ed 46 5198-5201... 

The [(NH3)4(NH2)Pt(ONO)] " complex as the Cl salt is known and can be converted to the nitro isomer in the soHd state by heating (130), and the nitro isomer to the nitrito isomer in aqueous solution by photolysis using 254 or 313 nm Hght (134), similar to the observation in the related [(NH3)5Co(N02)] complex. In 2001, Chaudhuri and coworkers provided evidence for a thermally induced nitro-to-O.O-nitrito linkage isomerization in diamine complexes of nickel(II) such as ira s-[NiL2(N02)2] (L = N,A/-dipropyl-l,2-diaminoethane) in the solid state as determined by X-ray crystallography (54). See Figure 22. 

Using cobalt(II) as template, the trans compoimd [Co(L15)](C104)2 can be obtain (220, 223]. Cobalt(III) appeared to be non-effective in syntheses of this type, presimiably because of formation of non-labile diamine complexes. The effectiveness of platinum(n) and palladium(II) as templates is reduced markedly compared to nickel(II) and copper(II) for the same reason [220]. Tris(ethylenediamine) iron(II) interacts with acetone in the presence of atmospheric oxygen according to Equation (2.113). 

To the first group belongs the determination of propylene diamine S ) This is based upon the formation of the copper-diamine complex, which is reduced at a potential different from that of the uncomplexed copper ion. Similarly, the determination of 1,2-diaminocyclohexane can be carried out in the presence of excess of hexamethylenediamine. ) It depends upon the fact that 1,2-diaminocyclohexane forms at pH ll-7-12-2 a complex compound with nickel ions which is reduced at —1-05 V. Hexa-methylenediamine at this pH does not form complexes and... 

Keywords C-2 Epimerization, Hydroxymethylated sugar. Stereospecific rearrangement,Nickel/ diamine complex, MetaUomicelle, Chirality of ligand... 

In an extensive series of studies, Yoshikawa,Yano and co-workers have confirmed that various kinds of aldose can be complexed with nickel and amino compounds such as diamines and amino acid in a methanolic solution [43]. They studied the nickel(ll) complexes coordinating N-glycosides derived from diamine and monosaccharide. The structure of the complex was determined from three-dimensional X-ray data [43 d]. Their further studies elucidated that aldoses can be epimerized by reaction systems containing a nickel/diamine complex. This novel epimerization proceeds through an alternative mechanism that is definitely distinct from the epimerization mechanism by reversible enolization that was introduced in Sect. 2.1. It results in the formation of an equilibrium mixture of the two epimers. According to their study [ 39], three significant pecu-harities of this epimerization are ... 

We know that functional groups are commonly the major factors controlling the reaction system. The reaction mechanism shown in Fig. 4 suggests that the intermediate ternary complex, nickel/diamine/sugar, governs the epimerization. It indicates that aldoses cannot be epimerized by a nickel ion or ethylenediamine alone. Formation of a ternary complex comprising of metal, sugar, and a diamine derivative is indispensable and a minimum requirement for the epimerization. We have carried out experiments to clarify whether an amine-type base... 

In order to develop a suitable catalytic system for nickel/diamine complex assisted epimerization of aldoses, various kinds of diamines were prepared and their influences on epimerization studied [44 a, c]. One of the most effective chemical alterations is W-alkylation of ethylenediamine. Due to the variety of alkyl chain lengths and degree of alkylation around nitrogen atoms, the stability of the complexes should be profoundly changed according to the steric interactions between the sugar and the ligand in the complex. 

Looking at it from another angle, it would be feasible to state that there are two prerequisites to accompHsh the epimerization of aldoses by a nickel complex. As the first requirement, the Ni(II)/diamine complex must have the abiUty to incorporate sugar and lead to the ternary complex. In this context, simple diamines such as free ethylenediamine and methylated ones have the potential to produce the ternary complex. As the second prerequisite, the resulting ternary complex must be appropriately unstable to undergo a mutation and a transition in the complex. 

It has been suggested that significant enhancement of the epimerization was due to the formation of metallomicelles in the reaction system. To confirm the existence of the micelles, the surface tension of the reaction system was measured. It was confirmed that hydrophobic Ni/diamine complexes containing alkyl chains longer than decyl form micelles, whereas Ni/diamine complexes containing alkyl chains shorter than nonyl do not. It should be emphasized that such formation of micelles was in accordance with the occurrence of epimerization. The fact that a nickel complex that can aggregate to form metallomicelles shows excellent epimerizing ability is the most noteworthy point. 

The classical method of epimerisation, the Lobry de Bruyn - Alberda van Ekenstein rearrangement has been treated by S. Angyal, the expert in the field of free sugars and their interconversions. L. Petrus and co-authors have contributed a first-hand experience based chapter on the Bflik reaction, which was discovered in Bratislava and is an important approach to rare sugars on a commercial basis. Another, more recently developed method, the epimerisation of free sugars catalysed by nickel (II)/ethylene diamine complexes, has been reviewed by S. Osanai. 

Other Metal Complexes Apart from metal complexes derived from BINOL, other metal complexes, such as the lithium-aluminum amiuo diol complex, " aluminum and nickel salen complex, ruthenium diamine complex, and ruthenium phosphinite diamine complex were also found applicable for the asymmetric Michael addition of 1,3-dicarbonyl compound to cyclic enone. All these metal complexes afforded about 90% of asymmetric induction in the Michael reaction of 2-cyclohexen-l-one and malonate. 

Azaarylacetates and acetamides, such as (399), have been reported to undergo Michael additions to nitroalkenes (394) in the presence of the nickel(II)-bis(diamine) complex 0 (401) and molecular sieves to produce (400) with >19 dr and <99% ee 0... 

---