Substitution Carbon Monoxide Replacement

While the replacement of carbon monoxide by a tertiary phosphine ligand represents one of the most fundamental substitution reactions in metal carbonyl chemistry, it was not until 1975, some 16 years after the... 

The dominant photochemical reaction of metal carbonyl compounds is loss of carbon monoxide, which is usually followed by substitution of another ligand to replace the expelled carbon monoxide. 

During the last few years, the PKR has been developed as a straightforward and practicable method for the synthesis of highly substituted cyclopentenones. But for many synthetic chemists, the employment of poisonous CO still represents a disadvantage. Hence, different strategies focused on the replacement of carbon monoxide within the reaction sequence. Recent successful examples are based on results from the early 1960s, which dealt with the transition metal catalyzed decarbonylation of organic oxo compounds [67]. 

The structure of the triphenylphosphine substitution product is known (29). The square pyramidal Ru6C core is retained, and the phosphine replaces one carbon monoxide from a basal Ru(CO)3 group in 10. The carbide carbon atom is situated 0.19 A below the square face of the pyramid (cf. 0.11 A in 10). 

Alkanes are fuels they burn in air if ignited. Complete combustion gives carbon dioxide and water less complete combustion gives carbon monoxide or other less oxidized forms of carbon. Alkanes react with halogens (chlorine or bromine) in a reaction initiated by heat or light. One or more hydrogens can be replaced by halogens. This substitution reaction occurs by a free-radical chain mechanism. 

The replacement of ligands of a metal carbonyl cation, either carbon monoxide or another ligand, serves as a valuable route to substituted cationic metal carbonyls. 

When nitrides are treated with carbon monoxide at moderate temperatures, two reactions occur. The first may be termed a completion reaction in which carbon enters the interstitial phase until C + N increases to about 0.5. This reaction is more rapid than the second, the substitution reaction in which carbon replaces nitrogen. Similar reactions are observed when carbides of iron (Hagg carbide or cementite) are... 

Spectroscopic studies were performed on Ni- and Co-substituted Rds and Dx [50] while Fe replacement was done for Mossbauer analysis [35]. The Dx derivatives containing Zn and " Cd in the protein s metal site have been analy2ed by 2D-NMR spectroscopy and the solution structures have been determined [38, 39]. NMR studies were also done with the Zn, Cd and " Hg derivatives for Rd [9, 22, 51, 52]. The Ni-containing derivative is of particular interest, as Ni-substituted Rd and Dx were shown to mimic the reactivity pattern of Ni-containing hydro-genases with respect to hydrogen production, deuterium-proton and inhibition by carbon monoxide [53]. However, there is no three-dimensional structure yet available for either the Rd or the Dx Ni-substituted proteins. 

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