Mononuclear complexes nickel

Muller, A. and Henkel, G. (1995) [Ni2(SC4H9)g] , a novel binuclear nickel-thiolate complex with NiS4 tetrahedra sharing edges and [Ni(SC( H4SiMe3)4] , a structurally related mononuclear complex ion. Z. Naturforsch., B50, 1464-8. 

The only apparently mononuclear complex of nickel(I) so far discovered is K3Ni(CN)4 (187). It is an extremely reactive substance obtained by reduction of K2Ni(CN)4 in strongly alkaline solution it has a magnetic moment of 1.73 B.M., which is the value expected for one unpaired electron. This compound may be compared with the complex acetylides prepared by... 

When simple nickel(II) salts are treated with thiols, in most cases stable thiolate-bridged polymers are formed. In a number of cases, treating these polymers with either tertiary phosphines or isocyanides gave mononuclear mixed-ligand complexes (equation 204).1951 These mononuclear complexes, due to the presence of terminal thiolates which possess lone pairs, can further react with nickel(II) and give trinuclear complexes (equation 205).1952... 

In 1959, the coordinated mercaptide ion in the gold(III) complex (4) was found to undergo rapid alkylation with methyl iodide and ethyl bromide (e.g. equation 3).9 The reaction has since been used to great effect particularly in nickel(II) (3-mercaptoamine complexes.10,11 It has been demonstrated by kinetic studies that alkylation occurs without dissociation of the sulfur atom from nickel. The binuclear nickel complex (5) underwent stepwise alkylation with methyl iodide, benzyl bromide and substituted benzyl chlorides in second order reactions (equation 4). Bridging sulfur atoms were unreactive, as would be expected. Relative rate data were consistent with SN2 attack of sulfur at the saturated carbon atoms of the alkyl halide. The mononuclear complex (6) yielded octahedral complexes on alkylation (equation 5), but the reaction was complicated by the independent reversible formation of the trinuclear complex (7). Further reactions of this type have been used to form new chelate rings (see Section 7.4.3.1). 

Precisely the last condition explains the fact that mainly ICC have been obtained by the immediate interaction of ligands and zero-valent metals. Thus, a large series of metal p-diketonates was synthesized in the absence of a solvent [513,634-638], for example, iron bis- and tra-acetylacetonates [635]. It was shown that other ligands can serve as activators or promoters in these processes. In particular, the introduction of a,a or y,y -bipy into the reaction mixture gives the possibility of isolating copper acetylacetonates and adducts of similar complexes of cobalt and nickel [636], meanwhile the p-diketonates of the metals above are not formed under conditions similar to those reported in Ref. 635. Under dissolution of more active metallic barium in the mixture of another p-dikctone - dipivaloyl-methane (DPM) - with dyglime (DG) or tetraglime (TG) in absolute pentane, the mononuclear complex [Ba(DPM)2(TG)] and binuclear complex [Ba2(DPM)4 ( t-H20)(DG)] were isolated and structurally characterized [637]. 

Condensation of ketones or aldehydes with the methyl ester of dithiocarbazic acid produces hgands with S,N,0 or S,N donor sets. An example is (142), which acts as both a didentate and a tridentate to ReO. Nickel(II)-templated reactions of pentanedione or salicylaldehyde with aminoethanethiol produce N,0,S ligands such as (143) and (144) these form simple mononuclear complexes or else dinuclear species with thiolate bridging two Ni centers. Mixed donor Schiff-base hgands including other heteroatoms such as P (145) and Te (146) have appeared. 

Recent kinetics studies on protonation of [Ni(SEt)((Ph2 PCH2CH2)2PPh)]+ (14) proposed that the proton interacts with both the nickel and sulfur sites,consistent with the proposal of intramolecular proton transfer between cysteinate sulfur and Ni atom in the Ni-based hydrogenases. Additionally, the mononuclear complex [Ni(psnet)]+ (15) of known structure and a mildly negative redox potential can stoichiometrically evolve H2 from protic sources. On the basis of kinetics analysis, the reaction paths considered most probable involve steps of protic oxidative addition to Ni(I) to generate Ni -H , and electron transfer to Ni(III) followed... 

The mononuclear carbonyls of nickel and iron that are liquid at the ambient temperatures are extremely flammable. Their vapors present flashback fire hazard. They also form explosive mixtures with air. Also, most mononuclear carbonyls that are solids at ambient conditions are pyrophoric. These include the carbonyls of vanadium and tungsten. All carbonyl complexes are air sensitive. Some of them ignite on prolonged exposure to air or may catch fire when opened to air after long storage. The dimeric and trimeric derivatives, however, are less pyrophoric than the mononuclear complexes. All carbonyl metal complexes are susceptible to explode on heating. They react violently with strong oxidants. 

Very few discogenic complexes with a hydrazone moiety have been so far studied. One nickel complex based on 2,6-diacetylpyridinebis(3,4,5-tridodecyloxybenzoylhydrazone) has been previously reported by Battistini et al. as a potential columnar metallomesogen." The mononuclear complex showed an apparently unidentified mesophase during the first heating which was not... 

Osakada has tested in parallel to Co/Zr complexes 49 described in Sect. 3.2.1, an analogous system with Pd and Ni as late metal partners [97]. Palladium was found to have no effect on the catalytic activity of zirconium, while the Ni/Zr complex 97b enables concomitant oligomerization at the nickel center and enchainment of the resultant branched oligomers to the polymer grown at the Zr center giving rise to polyethylene with methyl, ethyl, and long aUcyl branches. A control reaction performed with a mixture of the mononuclear complexes 47 and 96b gave also polymers but with almost no alkyl branches (Scheme 53). 

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