Nickel carbonyl clusters

Although Ni(CO)4 was discovered many years ago, no neutral Ni2(CO)x compound has ever been synthesized in macroscopic amounts. However, several communications report ionic species such as [Ni2(CO)8l+, [Ni2(CO)7], and [Ni2(CO)6]+, where structures with one or two bridging carbonyls are proposed.2418 Plausible structures for neutral Ni2(CO)x (x = 5, 6, 7) have been investigated by theoretical methods, and decomposition temperatures well below room temperature have been predicted.2419,2420 Tetra-, penta-, and hexanuclear nickel carbonyl clusters have been investigated by means of molecular orbital theory. It is found that the neutral forms are more stable than the corresponding anionic forms but the anionic forms gain in stability as the nuclearity rises.2421 Nickel carbonyl cluster anions are manifold, and structural systematics have been reviewed.2422,2423 An example includes the anion [Ni9(CO)i6]2- with a close-packed two-layer metal core.2424... 

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... 

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... 

E5.8 Structural systematics in nickel carbonyl cluster anions... 

The n.m.r. spectra of all presently known nickel carbonyl clusters have been reported and terminal/bridge carbonyl exchange is always found to occur on outer layers before inner layers. ... 

The carbonyl clusters provide an interesting set of models for the chemisorption of CO on nickel. It is very interesting that, for the Ni (CO) assignments, a plot of Pco versus 1/n for the three-center-bonded CO moieties extrapolates to 1950 cm for = oo (the "chemi-... 

Nickel carbonyl radicals show an even greater tendency than cobalt carbonyls to cluster in a krypton matrix. Three binuclear nickel carbonyls have been detected by EPR spectroscopy in the products of y-irradiated Ni(CO)4 in Kr, yet no mononuclear species has been positively identified (65). 13C hyperfine structure has... 

Stereochemistry of Monohydrido- and Dihydrido-Dodecanickel Carbonyl Clusters Containing a Hexagonal Close Packed Nickel Fragment... 

BROACH ET al. Carbonyl Clusters Containing a hep Nickel Fragment 97... 

J. C. Calabrese, L. F. Dahl, A. Cavalieri, P. Chini, G. Longoni, and S. Martinengo, Synthesis and Structure of a Hexanuclear Nickel Carbonyl Dianion, [Ni3(CO)3( j,2-CO)3]22, and Comparison with the [Pt3(CO)3(p2-CO)3]22 Dianion. An Unprecedented Case of a Metal Cluster System Possessing Different Metal Architectures for Congener Transition Metals, J. Am. Chem. Soc. 96, 2616-2618 (1974). 

Although anionic species with nickel in the oxidation state -I have been postulated, such as [Ni2(CO)6]2, these have not been confirmed. Nickel does, however, form a number of anionic carbonyl clusters with higher nuclearity, e.g., [Ni5(CO)l2]2-, in which the metal carries a partial negative charge. 

The area of alkyne cluster chemistry has been the subject of two previous review articles. The first is concerned largely with alkyne-cobalt chemistry (16), while the second provides a comprehensive, systematic review of alkyne-substituted homo- and heterome-tallic carbonyl clusters of the iron, cobalt, and nickel triads (17). This latter review covers the literature up to the end of 1981. The present work does not set out to be fully comprehensive, but rather reflects the authors own interests in the subject. A number of key examples are... 

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