Isocyanides complexes

L. Malatesta and I-. Bonatt, Isocyanide Complexes of Metals, Wiley. London, 1969, 199 pp. 

Isocyanide complexes [68] can readily be prepared using excess isocyanide as the reducing agent ... 

Hydride complexes NMR spectra Hydroxide Infrared spectra Isocyanide complexes Isomerism in complexes... 

Isocyanide complexes of metals. L. Malatesta, Prog. Inorg. Chem., 1959,1, 283-379 (117). 

Recent advances in the chemistry of isocyanide complexes. F. Bonati and G. Minghetti, Inorg. Chim. Acta, 1974, 9, 95-112 (238). 

The isocyanide ligand, CNR, is formally isolobal with a carbene ligand. Several studies have investigated iron(Ill) porphyrin isocyanide complexes which have the general formula [FeCPorKCNR) ]. However, these studies have mostly been concerned with spin state and spectroscopic properties rather than chemical transformations and will not be discussed in detail here. Crystallographic details are given for two of the complexes. " ... 

B. Nucleophilic Reactions with Metal Isocyanide Complexes... 

While on the subject of reviews, attention should also be directed to a very recent collection of articles on isocyanide chemistry edited by Ugi 156). This volume is oriented somewhat toward the organic chemistry of isocyanides, but not with the complete exclusion of metal complexes of these species one is directed in particular to the chapters by Vogler (Chapter 10) on coordinated isocyanides and by Saegusa and Ito (Chapter 4) on a-additions to isocyanides. These latter reactions are often catalyzed by copper(I) compounds and occasionally by other metal complexes as well, and it is believed that this catalysis is accomplished by intermediate formation of metal isocyanide complexes. 

There is a 1968 review of metal isocyanide complexes in Japanese (122) this is not generally accessible, however. 

The subjects of structure and bonding in metal isocyanide complexes have been discussed before 90, 156) and will not be treated extensively here. A brief discussion of this subject is presented in Section II of course, special emphasis is given to the more recent information which has appeared. Several areas of current study in the field of transition metal-isocyanide complexes have become particularly important and are discussed in this review in Section III. These include the additions of protonic compounds to coordinated isocyanides, probably the subject most actively being studied at this time insertion reactions into metal-carbon bonded species nucleophilic reactions with metal isocyanide complexes and the metal-catalyzed a-addition reactions. Concurrent with these new developments, there has been a general expansion of descriptive chemistry of isocyanide-metal complexes, and further study of the physical properties of selected species. These developments are summarized in Section IV. 

Incidentally, isocyanides are polar (for CNC H, the dipole moment is 3.44 D) and they are good bases (vs. BRj, H+), whereas CO is a poor base hence isocyanides can function as ligands in metal complexes where carbon monoxide does not. The scarcity of low-valent isocyanide complexes is less easily explained, however. Arguments involving 77-acceptor capacity are quite inappropriate. More data on low-valent species, and evaluations of stabilities, modes of decomposition, and reactions are desirable. 

The reactions of nucleophilic reagents with cationic and uncharged metal carbonyl complexes have received much attention in the past, and it is not surprising that these studies have now been extended to isocyanide metal complexes. Different products in these reactions can arise by three general routes these include ligand substitution, reactions involving attack at a ligand, and reduction of the metal complex. All have been observed in reactions with metal isocyanide complexes. 

The susceptibility of a metal complex to nucleophilic attack is enhanced by a positive charge on the complex. This fact, and the fact that most metal isocyanide complexes are cationic, probably explains why no nucleophilic reactions of uncharged isocyanide complexes have yet been reported. It is... 

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