Nickel carbonyl derivatives cobalt

As, for the most part, the corresponding ester derivatives are a more important synthetic target, recent literature has demonstrated methods to prepare the esters directly. Examples include the use of nickel carbonyl in a methanol/dimethylformamide solvent system(37) the direct conversion of benzyl alcohol to methylphenyl-acetate using cobalt carbonyl(38) and a reaction system which utilizes an ammonium salt bound to an organic polymer(39). 

In 1980 we published a survey (1) of our major results in this area as of late 1979. These results include extensive work on binuclear CF N PF complexes of cobalt (2,3,4,5) and nickel (6). This paper summarizes our more recent results in this area with particular emphasis on binuclear complexes of chromium, molybdenum, and tungsten as well as some new results on iron carbonyl derivatives. 

In addition to its importance in alloys (for example, alnico, vicalloy, and stellite), cobalt is of use as a catalyst in the Fisher-Tropsch process in which carbon monoxide is hydrogenated to a mixture of hydrocarbons. It appears likely here that one or more carbonyl derivatives of cobalt act as intermediates. Nickel is of importance in a number of alloys Monel metal, alnico, stainless steel, etc.). In a very finely divided state Raney nickel), it is of use to the organic chemist in hydrogenation reactions, for it will absorb large quantities of hydrogen gas with probable breakage of the molecules to atoms (p. 27). 

It should be noted that cyclobutadiene always replaces carbon monoxide in reactions with metal carbonyl derivatives. Yields of product parallel the known rate of exchange of CO in the starting carbonyl 184). Highest yields of ligand transfer products are attained with nickel and cobalt carbonyls which are known to very rapidly exchange their CO groups by a D-type mechanism 185-188). Lowest yields have been reported with Mo and W complexes, the carbonyls of which exchange with CO very slowly 188). 

Ryang and Tsutsumi at Osaka University obtained an acyloin from alkyllithium and Ni(CO)4 (Eq. (5.56)) [64]. Later, Corey and Hegedus applied this ob.servation to an acyl group tran.sfer reaction using nickel carbonyl (Eq. (5.57)) [65] and a cobalt carbonyl derivative [66]. 

Hydrocarboxylation is the formal addition of hydrogen and a carboxylic group to double or triple bonds to form carboxylic acids or their derivatives. It is achieved by transition metal catalyzed conversion of unsaturated substrates with carbon monoxide in the presence of water, alcohols, or other acidic reagents. Ester formation is also called hydroesterification or hydrocarb(o)alkoxylation . The transition metal catalyst precursors are nickel, iron or cobalt carbonyls or salts of nickel, iron, cobalt, rhodium, palladium, platinum, or other metals4 5. 

The stoichiometric carbonylation of olefins and their derivatives may also be achieved without pressure at room temperature (in special cases even at lower temperatures). With catalytic amounts of cobalt hydrocarbonyl, temperatures between 100 and 260 °C and pressures from 30 upward to 900 atm are applied. In the carbonylation of saturated alcohols, cobalt catalysts are preferred, which are already highly active at 180 C, whereas nickel carbonyl requires a reaction temperature of 280 °C to give the same results [371]. 

Like cobalt, nickel occurs as sulfide and arsenide minerals, e.g. pentlandite, (Ni,Fe)9Sg. Roasting such ores in air gives nickel oxide which is then reduced to the metal using carbon. The metal is refined electrolytically or by conversion to Ni(CO)4 followed by thermal decomposition (eq. 21.4). This is the Mondprocess, which is based on the fact that Ni forms a carbonyl derivative more readily than any other metal. 

A similar addition to alkynes results in the formation of the corresponding unsaturated acids and derivatives.14,23,121-124 Cobalt, nickel, and iron carbonyls, as well as palladium complexes, are the most often used catalysts.14... 

Eventually we formed carbonyls in the liquid phase by redox disproportionation of nickel and cobalt derivatives of organic thioacids. In the reaction between nickel(II) dithiobenzoate and carbon monoxide in the presence of HS ion we assumed the formation of a sulfur-bridged nickel(IV) complex (VII, 32). More recent investigations (84), however, have shown that half the nickel appears as a monomeric nickel(II) complex of the same empirical formulation, formed by insertion of a sulfur atom in the dithio ligand, the other half of the nickel being reduced to nickel(O) by the sulfide. 

This potassium salt, K4Ni2(CN)6, may be further reduced by potassium in liquid ammonia to yield a yellow substance, K4Ni(CN)4. This has nickel in the zero-valent state and is thus comparable to the metal carbonyls, Fe(CO)5 and Ni(CO)4 (p. 157), to cobalt nitrosyl carbonyl Co(CO)4NO, and to the metal ammoniates Ca(NH3)6 and Pt(NH3)2. However, K4Ni(CN)4, and the closely related acetylene derivative, K4Ni(C=CH)4, are especially unusual, for in them, the zero-valent metal has been incorporated into an anion, whereas in the carbonyls and metal ammoniates, the zerovalent metals are present as uncharged species. 

A plausible mechanism for the reaction includes several organometallic species that are sensitive to reactive moieties elsewhere in the molecule. If a chloro, chloromethyl, or mesyloxymethyl substituent is attached vicinal to the 1,1 -dibromo moiety, efficient ring opening occurs prior to carbonylation and P,y- and y, -unsaturated acid derivatives are formed. Reductive carbonylation has also been achieved with 1,1-dibromocyclopropanes using an excess of pentacarbonyliron in dimethylformamide with added methanol or sodium methoxide, or cobalt(II) chloride and nickel(ll) cyanide under phase-transfer conditions in a carbon monoxide atmosphere. However, the yield of cyclopropanecarboxylic acid derivatives is low, and when pentacarbonyliron is used the amount of monobromides is fairly high. ... 

Stable binary metal carbonyls, negatively charged or uncharged, exist for all the elements of the 3d, 4d, and 5d transition series from CSroup 4 to Group 10, with the exception of palladium. As shown in Table 1, some of the elements (Ti, Zr, Hf, Nb, Ta, and Pt) have anionic carbonylmetalates only and no stable uncharged derivatives have so far been reported. Of the known metal carbonyls, only those of Group 6, Group 7 (with the exclusion of technetium), iron, ruthenium, cobalt and nickel have been used much in catalytic processes. 

The advent of hindered, unsymmetrically substituted, perfluoroalkynes such as CFa C C-C(C2F5)2-CF3 3 and CF3 CiC-C(CF3)s should lead to the construction of even more complex complexes The former alkyne reacts with nickel and cobalt carbonyls, but not with iron carbonyls. Alkynyl complexes derived from cobalt carbonyls have been reviewed. ... 

Nickel is the only metal to react directly with carbon monoxide at room temperature at an appreciable rate, although iron does so on heating under pressure. Cobalt affords HCo(CO)4 with a mixture of hydrogen and carbon monoxide (p. 387). In general, therefore, direct reaction does not provide a route to metal carbonyls. The metal atom technique (p. 313) has been used to prepare carbonyls of other metals in the laboratory e.g. Cr(CO)g, but it offers no advantages over the reduction method discussed below. When metal vapours are cocondensed with carbon monoxide in frozen noble gas matrices at very low temperatures (4-20K) the formation of carbonyl complexes is observed. These include compounds of metals which do not form any stable isolable derivatives e.g. Ti(CO), Nb(CO) and Ta(CO)g as well as Pd(C0)4 and Pt(C0)4. Vibrational spectra of the matrix show that coordinatively unsaturated species such as Ni(CO) n = 1-3) or Cr(CO) (n = 3-5) are also formed under these conditions. 

In most of the few metal carbonyl and cyclopentadienyl derivatives without an inert gas configuration for the central metal atom, such as V(CO)g, Cr(CO)5l 87), C5H5VC7H7 88), and CsHsCrCgHe 89), the metal atom has exactly one electron less than the inert gas configuration. The only exceptions to this are the biscyclopentadienyl derivatives of vanadium, chromium, cobalt, and nickel in which the central metal atom has neither the inert gas configuration nor one electron less than this configuration. 

The first type of process can be catalyzed by derivatives of palladium, nickel and cobalt, according to basically the same scheme of the catalytic cycle, involving oxidative addition of the reduced form of the metal catalyst across the R-X bond, insertion of CO to form a a-acyl complex, which is then cleaved by the nucleophile to form the final product and regenerate the catalyst. Alternatively, the nucleophile may attack the carbonyl ligand with subsequent reductive elimination. This mechanism is also reasonably... 

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