Nickel complexes clusters

The dependence of rate constants for approach to equilibrium for reaction of the mixed oxide-sulfide complex [Mo3((i3-S)((i-0)3(H20)9] 1+ with thiocyanate has been analyzed into formation and aquation contributions. These reactions involve positions trans to p-oxo groups, mechanisms are dissociative (391). Kinetic and thermodynamic studies on reaction of [Mo3MS4(H20)io]4+ (M = Ni, Pd) with CO have yielded rate constants for reaction with CO. These were put into context with substitution by halide and thiocyanate for the nickel-containing cluster (392). A review of the chemistry of [Mo3S4(H20)9]4+ and related clusters contains some information on substitution in mixed metal derivatives [Mo3MS4(H20)re]4+ (M = Cr, Fe, Ni, Cu, Pd) (393). There are a few asides of mechanistic relevance in a review of synthetic Mo-Fe-S clusters and their relevance to nitrogenase (394). 

Initial attack of hydroxide ions onto Ni(CO)4 gives as yet uncharacterized species,1 which readily condense with unreacted Ni(CO)4 to give variable mixtures of [Ni5(CO)12]2- and [Ni6(CO)12]2-. Hydrolysis of [Ni5(CO)12]2- in water produces [Ni6(CO)12]2-, according to the above reaction. The dianion [Ni CO) 2]2- is isolated as the tetramethylam-monium salt in a crystalline state in 70% yield. The [Ni6(CO)12]2 dianion is a starting material for the synthesis of several other homo- and heteromet-allic nickel carbonyl cluster complexes.1-9... 

Examples of nickel complexes are rare and are confined to three reported nickel carbonyl clusters containing interstitial germanium or tin atoms (90). The reaction between [Ni6(CO)l2]2 and GeCl4 affords two species, [Ni10Ge(CO)2o]2 , 79, and [Ni12Ge(CO)22]2, 80. The former structure is based on a pentagonal antiprismatic framework of nickel atoms with an... 

The metal(O) isocyanide clusters Ni4(CNBu )7 (45)5 (60), Pt3(CNBu )6 (46) (23) and Pt7(CNXylyl),2 (47) (20) have been characterized crystallographi-cally. In the nickel complex the nickel atoms define the vertices of a highly compressed C3v tetrahedron, with each nickel having a terminal isocyanide and three basal nickel atoms joined by three four-electron donor isocyanide ligands. The unusual feature of the structure of Pt7(CNXylyl),2 is that one... 

Di(carbene)gold(I) salts, oxidation, 2, 293—294 Dicarbido clusters, with decarutheniums, 6, 1036 Dicarbollide amides, with tantalum, 5, 184 Dicarbollide thorium complexes, synthesis and characterization, 4, 224—225 Dicarbollyl ligands, in nickel complexes, 8, 185 Dicarbonyl complexes arylation with lead triacetates diastereoselectivity, 9, 389 enantioselectivity, 9, 391 mechanisms, 9, 387 reaction examples, 9, 382 indium-mediated allylation, 9, 675 with iridium, 7, 287 reductive cyclization, 10, 529 in Ru and Os half-sandwiches, 6, 508 with Zr—Hf(II), 4, 700... 

Hydrothermal methods, for molecuarlar precursor transformation to materials, 12, 47 Hydrotris(3,5-diisopropylpyrazolyl)borate-containing acetylide, in iron complex, 6, 108 Hydrotris(3,5-dimethylpyrazolyl)borate groups, in rhodium Cp complexes, 7, 151 Hydrotris(pyrazolyl)borates in cobalt(II) complexes, 7, 16 for cobalt(II) complexes, 7, 16 in rhodium Cp complexes, 7, 151 Hydrovinylation, with transition metal catalysts, 10, 318 Hydroxides, info nickel complexes, 8, 59-60 Hydroxo complexes, with bis-Cp Ti(IV), 4, 586 Hydroxyalkenyl complexes, mononuclear Ru and Os compounds, 6, 404-405 a-Hydroxyalkylstannanes, preparation, 3, 822 y-Hydroxyalkynecarboxylate, isomerization, 10, 98 Hydroxyalkynes, in hexaruthenium carbido clusters, 6, 1015 a-Hydroxyallenes... 

Grignard additions, 9, 59, 9, 64 indium-mediated allylation, 9, 687 in nickel complexes, 8, 150 ruthenium carbonyl reactions, 7, 142 ruthenium half-sandwiches, 6, 478 and selenium electrophiles, 9, W11 4( > 2 in vanadocene reactions, 5, 39 Nitrites, with trinuclear Os clusters, 6, 733 Nitroalkenes, Grignard additions, 9, 59-60 Nitroarenes, and Grignard reactivity, 9, 70 Nitrobenzenes, reductive aminocarbonylation, 11, 543... 

The tetrahedral [160-163] and cis-planar [100,134,164-167] structures are characteristic for chelates of type 874 with coordination units NiN4 and MN2S2, respectively, as well as chelates 868 discussed above. Original polyhedral forms were discovered by x-ray diffraction for nickel and palladium ICC of the discussed type 874. It is accepted that, in case of a nickel complex, the compound with a carbon-carbon bond 875 is formed [165,166] formation of palladium chelates is accompanied by the cyclometallation reaction leading to tetranuclear clusters 876, where the tridentate ligand behaves as C,N,S-donor [168]. 

A few years ago Smalley and coworkers were able to obtain detailed experimental information about the reactivity of specific transition metal clusters with hydrogen molecules (1). The results for copper and nickel clusters were essentially as expected from the known results for surface and metal complex activities. For copper no clusters were able to dissociate whereas for nickel all clusters were active with a slow, steady increase of activity with cluster size. For the other transition metals studied, cobalt, iron and niobium, a completely different picture emerged. For these metals a dramatic sensitivity of the reactivity to cluster size was detected. No convincing explanation for these surprising results has hitherto been suggested. It should be added that there are no dramatic differences in the activity towards Hg for the metal surfaces (or the metal complexes) of nickel on the one hand and iron, cobalt and niobium on the other. 

The abundant chemistry of Ni(CO>4 under reductive reaction conditions leading to the formation of dinuclear nickel complexes or even to nickel clusters suggests the involvement of higher aggregates, however. An overview of the reactivity of nickel complexes, and of Ni(CO)4 in particular, is given in a series of excellent reviews by Jolly [13]. There seems to be evidence of an autocatalytic cycle for the formation of the active catalyst [14]. Parallel to this, the water-gas shift reaction (eq. (5)) occurs, resulting in the formation of carbon dioxide and hydrogen, which is known to form metal hydrides in the presence of metal carbonyls [15]. 

E5.4 Formation of platinum and palladium clusters with carbonyl and phosphine ligands E5.5 Reactivity and flexibility in platinum metal clusters E5.6 Excited state properties of the low-valent bi- and trinuclear complexes of palladium and platinum E5.7 Interstitial nickel carbonyl clusters... 

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