Nickel carbonyl structure

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... 

A blue, impure and probably polymeric solid, produced from reaction of nitric oxide and nickel carbonyl, decomposed with incandescence at 90° C. The structure is very doubtful but a dinitrosyl was tentatively postulated. A trinitrosyl, [115380-62-6], has been listed recently. 

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... 

The sintered electrode constructions are gradually replaced with structures of higher capacity as, for example, felted nickel fibril or foam structures [350-352]. An open nickel foam structure can be obtained by vapor deposition of nickel from nickel carbonyl into a bed of urethane foam and then burning off the polymer. The porosity increases from 80% typical for sinter electrodes and reaches 90-95% for felted or foam structures. Application of polymer bonded cadmium electrodes significantly reduces environmentally dangerous dusting during cell production [350]. 

The deep-red, crystalline compound Ci0H14Ni, prepared by treating nickel carbonyl with cyclopentadienc, was first thought to have the structure dicyclopentadienenickel(O) [Ni(C6H6)2] (87). This compound has now been shown by nmr spectroscopy to have the structure T-cyclopentadienyl-7r-cyclopentenylnickel(II) (XLV), [Ni(7r-C5H6)(71--C6H7)] (70, 89,129). This... 

Nickel carbonyl is by far the best-known of these compounds. All the data support a tetrahedral structure with four equivalent, linear Ni—C—0 arrangements. The Raman (3, 62, 61) and infrared spectra (8, 53, 135, 136) have been investigated and various assignments of the fundamental frequencies have been put forward on the basis of Td symmetry (53, 136, 208). Several approximate coordinate analyses have been made using these assignments, but the spectra of isotopically substituted species have not been measured, so exact evaluations of force constants have not yet proved possible. The Ni—C and C—0 stretching force constants are particularly important and the values obtained by workers using various approximations are included in Table I. 

In summary, it can be seen that the structural chemistry of the zero-valent complexes has to date been dominated by investigations on nickel carbonyl. Preliminary studies on other compounds indicate that the tetrahedral structure may not be the only possibility, and thorough investigation of the unsaturatcd species is likely to develop. Back-donation may be examined by study of force constants, in favorable cases merely of observed frequencies, and it would be interesting to see more cases of competition for back-donation, as in (MeNC)3Ni(CO). 

What is the composition of iron, cobalt, and nickel carbonyls Consider the structure of the carbonyls of these elements from the standpoint of the valence bond theory. 

The discovery that the iron-group elements can form bonds which have in part the character of multiple bonds by making use of the orbitals and electrons of the 3d subshell, whilq surprising, need not be greeted with skepticism the natural formula for a compound ECO is that with a double bond from R to C, and the existence of the metal carbonyls might well have been interpreted years ago as evidence for double-bond formation by metals. The double-bond structure for nickel tetracarbonyl (structure E) was in fact first proposed by Langmuir62 in 1921, on the basis of the electroneutrality principle, but at that time there was little support for the new idea. 

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... 

FIGURE 7. Structure of silylene-nickel carbonyl complex, 75. Reproduced by permission of The Royal Society of Chemistry from Reference 149. 

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). 

Write an electronic structural fomjula for nickel carbonyl, and discuss the arrangement of the electrons around the nickel atoms in relation to the structure of krypton. Iron forms a carbonyl Fe(CO)5, chromium a car bonyl Cr(CO)g discuss the electronic structures of these substances. 

Other possible structures for nickel carbonyl are X, in which the nickel is positively charged and employs nine unpaired electrons in bond formation ... 

Some iron and nickel cyanide and carbonyl complexes have been reported as models of the [FeNi]-hydrogenase enzymes. The preparation and structures of the trigonal bipyramidal nickel and iron complexes with the tetradentate ligands tris(2-phenylthiol)phosphine (PS3) and tris(3-phenyl-2-thiophenyl)phosphine (PS3 ) have been reported [70, 71]. The nickel carbonyl complex [Ni(PS3 )(CO)] exhibits vco at 2029 cm compared with the value of 1940 em" for the iron earbonyl complex [Fe(PS3 )(CO)]. Both of these complexes lose CO upon oxidation. The use of cyanide in place of carbon monoxide allows for the preparation of both [Fe (PS3)(CN)] and [Fe (PS3 )(CN)] eomplexes. The IR properties of... 

This scheme implies addition reactions followed by substitution reactions, but the intermediate stages have not been identified. The NO2 substitution reactions are no doubt similar in principle to, but rather more complicated than, the reaction between nickel carbonyl and nitrogen dioxide (see below). The structure of the product, and the bonding of the NO2 groups to the metal, are discussed in connection with the nickel compound, which has been more fully investigated. 

Iron Pentacarbonyl. In its reactions with liquid dinitrogen tetroxide this compound follows the pattern outlined above, and the remarks on reactions of nickel carbonyl probably apply here also. The solvate, Fe(N03)3.N204, is produced (4). This has the structure N0+[Fe(N03)4] in the solid state it is volatile without decomposition, and is believed to be a five-coordinate complex, Fe(N0)(N03)4, in the vapor state. We have not yet succeeded in isolating the simple trinitrate, Fe(N03)3, by removal of N2O4. 

The spectrum of carbon monoxide adsorbed on nickel oxide prepared at 200° may be divided into two regions (Table I, la) (60). The first includes two bands at 2060 and 1960-1970 cm i, the second three bands at 1620, 1575, and 1420-1440 cm-i. Bands at 2060 and 1960-1970 cm- are typical of carbonyl structures and are found in the spectrum of carbon monoxide on metallic nickel (61). It has been suggested by some authors (62) that, in our experiments, these bands were also produced by the adsorption on the metal, the oxide being supposed oxygen-deficient. Chemical analyses (30) have shown, however, that, NiO(200°) contains an excess of oxygen and magnetic susceptibility measurements (33) have demonstrated that the quantity of metal is very small. Since the intensity of these bands is strong, we believe that they are not produced exclusively by the chemisorption of carbon monoxide on the metal but mainly by the adsorption on exposed nickel ions. 

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