Iron complexes alkyl cyanides

The well-known alkylation of ferrocyanide ion to form isocyanide iron complexes (48) can be explained by an insertion mechanism if the metal is alkylated initially, and then metal alkyl adds across a cyanide group. This mechanism also explains how external radioactive cyanide ion can enter the isocyanide ligands (48). 

Complex 376 can be prepared from enantiomerically pure rhenium precursor 381. The former can be deprotonated at low temperatures initiating the [2,3]-sigmatropic rearrangement to diastereomerically pure homoallylic sulfide complex 377. After S-alkylation, cyanide treatment releases the S ligand as product 379. As an extension of this work the authors showed that iron and ruthenium complexes can be used, too [219]. 

Yamazaki s complex (Structure 5) contains two alkyne molecules linked together to form a five-membered metallacycle. Arene-solvated cobalt atoms, obtained by reacting cobalt vapor and arenes, have been used by Italian workers to promote the conversion of a,w-dialkynes and nitriles giving alkynyl-substituted pyridines [20]. -Tolueneiron(0) complexes have also been utilized for the co-cyclotrimerization of acetylene and alkyl cyanides or benzonitrile giving a-substituted pyridine derivatives. However, the catalytic transformation to the industrially important 2-vinylpyridine fails in this case acrylonitrile cannot be co-cyclotrimerized with acetylene at the iron catalyst [17]. 

Nucleophilic attack on ( -alkene)Fp+ cations may be effected by heteroatom nucleophiles including amines, azide ion, cyanate ion (through N), alcohols, and thiols (Scheme 39). Carbon-based nucleophiles, such as the anions of active methylene compounds (malonic esters, /3-keto esters, cyanoac-etate), enamines, cyanide, cuprates, Grignard reagents, and ( l -allyl)Fe(Cp)(CO)2 complexes react similarly. In addition, several hydride sources, most notably NaBHsCN, deliver hydride ion to Fp(jj -alkene)+ complexes. Subjecting complexes of type (79) to Nal or NaBr in acetone, however, does not give nncleophilic attack, but instead results rehably in the displacement of the alkene from the iron residue. Cyclohexanone enolates or silyl enol ethers also may be added, and the iron alkyl complexes thus produced can give Robinson annulation-type products (Scheme 40). Vinyl ether-cationic Fp complexes as the electrophiles are nseful as vinyl cation equivalents. ... 

The recently confirmed inhibition of cytochrome P-450 by Isoniazid and hydralazine does not result from heme alkylation but rather from the formation of a transient complex with an absorption maximum at 449 nm.41-44 xjjg complex and its inhibitory effect are dissipated by ferrl-cyanide. The Inhibition by isoniazid thus resembles that mediated by 1,1-disubstituted hydrazines, which also form reversible cytochrome P-450 complexes absorbing at 449 nm. 5 studies with metalloporphyrins indicate that 1,1-dialkyIhydrazines are oxidized to amlnonitrenes that coordinate to the iron atom. The coordination of diazene metabolites with the heme of cytochrome P-450 also yields complexes with an absorbance maximum at 446 nm. ... 

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