Isonitrile complexes ligands

The syntheses of iron isonitrile complexes and the reactions of these complexes are reviewed. Nucleophilic reagents polymerize iron isonitrile complexes, displace the isonitrile ligand from the complex, or are alkylated by the complexes. Nitration, sulfonation, alkylation, and bromina-tion of the aromatic rings in a benzyl isonitrile complex are very rapid and the substituent is introduced mainly in the para position. The cyano group in cyanopentakis(benzyl isonitrile)-iron(ll) bromide exhibits a weak "trans" effect-With formaldehyde in sulfuric acid, benzyl isonitrile complexes yield polymeric compositions. One such composition contains an ethane linkage, suggesting dimerization of the transitory benzyl radicals. Measurements of the conductivities of benzyl isonitrile iron complexes indicate a wide range of A f (1.26 e.v.) and o-o (1023 ohm-1 cm.—1) but no definite relationship between the reactivities of these complexes and their conductivities. 

The problem of to what extent and how the reactivity of the isonitrile ligand is altered by coordination to a metal has an important bearing on the function of transition metals as homogeneous catalysts. It is also of interest from the standpoint of energy transfer in vivo, to determine whether or not there is any correlation between the reactivities of isonitrile complexes and their conductivities. In this paper we summarize some recent work on the syntheses and reactions of iron isonitrile complexes. 

A general method for the preparation of iron isonitrile complexes is the addition of the isonitrile ligand to iron (II) perchlorate (33) ... 

In connection with our studies of the reactions of coordinated ligands, we have investigated several additional syntheses of iron isonitrile complexes. 

Influence of the cis and trans Ligands in Octahedral Isonitrile Complex on the... 

Structurally characterised molecules with seven identical ligands are restricted mainly to some fluoro complexes [MF7]-, aquo complexes [M(H20)7]2+, isonitrile complexes [M(CNR)7]2+ and cyanide complexes [M(CN)7]. The stereochemistries are distributed along the long valley connecting the capped trigonal prism and the pentagonal bipyramid. 

Spectroscopic data show that the olefin monocyanocarbonylferrates and -ruthenates and their derived isonitrile complexes occur as two isomeric forms, in which the CN or isonitrile ligand occupies either an apical or basal position in a square-pyramidal structure. 

Fig. 31. A comparison of the 1H chemical shifts for the E11 valine 72-CH3 protons of the various isonitrile complexes of isolated a chains (o) and p chains (A) of Hb A, the o ( ) and p ( ) chains as identified within an intact Hb A molecule, and sperm whale myoglobin ( ). Ligands CO, carbon monoxide M, methyl isocyanide E, ethyl isocyanide P, n-propyl isocyanide B, n-butyl isocyanide iP, isopropyl isocyanide and tB, tert-butyl isocyanide. [From Mims et al. (1983a)].

Isonitrile complexes are formed by ligand-exchange reactions " M—L + RNC---------------------------- M—CNR -I- L... 

Ligand-exchange reactions of complexes having 7c-bonded hydrocarbon ligands are employed to prepare isonitrile complexes. Among these, 1,5-cyclooctadiene (COD) is... 

The second case involves attack of R-Y-H on the electron-deficient carbon of the isonitrile ligand, followed by proton transfer. It is adjustable with regard to nucleophile since amines (Y = N), unhindered alcohols (Y = O), and thiols (Y = S) add to the isonitrile carbon to form the corresponding diamino, aminoalkoxy, and aminothio carbenes. Isonitrile complexes of several different metals undergo this reaction, although Pd and Pt complexes have been the most thoroughly investigated.25... 

The [Rh ri -TMPP)2] [TMPP = tris(2,4,6-trimethoxyphenyl)phosphine] complex reacts reversibly with CO and isonitriles to form stable square-planar diamagnetic carbonyl and isonitrile complexes (13, 14). In the octahedral [Rh ri -TMPP)2] complex, the two TMPP ligands are coordinated to rhodium(II) with the two P donors in mutual cis positions. Four methoxy... 

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