Isonitrile, structure

In valence bond terms, the isonitrile (isocyanide) group requires representation as two resonance structures (140a) and (140b), but physical properties indicate that the dipolar contribution (140a) is the major one. The isonitrile structure involves divalent carbon, a property shared only with carbon monoxide and fulminates (R—O—NC) as isolable entities. Since the latter are notoriously reactive materials, this singles out the isonitriles as the only stable family of organic compounds which are formally divalent. 

Reaction of iodoethane with CN yields a small amount of isonitrile, CH3CH2N = C, along with the nitrile CH CE C N as the major product. Write electron-dot structures for both products, assign formal charges as necessary, and propose mechanisms to account for their formation. 

Schneider, W., Sladek, A., Bauer, A., Angermaier, K. and Schmidbaur, H. (1997) Structural Investigation of Bis(isonitrile) gold(I) Complexes. Zeitschriftfur Naturforschung B. A Journal of Chemical Sciences, 52, 53-56. 

The first transition metal isonitrilate complex reported was the tetrahedral Co-1 complex [Co(C=NPh )4] where Ph = 2,6-Me2C6H3,96 characterized by a crystal structure analysis. Oxidation yields the zerovalent dimer Co2(C=NPh )8, which features two bridging isonitrile groups. 

The matter was settled in 1994 in back-to-back communications by Gould [12] and Dmitrienko [13]. Gould showed that treatment of natural prekinamycin with dirhodium tetraacetate in methanol yielded the fluorene 16 (Scheme 3.1). The vinyl proton formed in this reaction (H-l) provided a critical spectroscopic handle and allowed unambiguous determination of the carbocyclic structure, excluding the presence of an indole heterocycle. In parallel, his research group obtained a high-quality crystal structure of a kinamycin derivative. The refined data set was shown to best accommodate a diazo rather than cyanamide (or isonitrile) function. 

In the following sections, we will review the marine isonitriles by skeletal types. This permits comparison of their differences and may suggest biogenetic clues. Skeletal frameworks are generally revealed by reducing the isonitrile with lithium/ethylamine to the corresponding hydrocarbon. Where trivial names have been assigned for skeletal types and for compounds, we shall use these as reported in the literature. In some cases, when structures related to previously mentioned compounds are discussed, formula numbers will be employed. 

Fattorusso s group, which earlier had discovered 48-50 in Axinella cannabina, reported the occurrence of another spiroaxane series, 51 and 52, from Acanthella acuta. The habitat of the latter sponge is the Bay of Naples. As was the case with other metabolites reported in their recent studies, the investigators deduced the structures of isonitrile 51 and iso thiocyanate 52 chiefly by 2D NMR methods. 

Polymeric (isocyanide)gold(i) aryls ( gold oligo-phenylene-ethynylene-isonitriles ) were tested as electrical conductors at metal-molecule-metal junctions (7r-conjugated molecular wires), but the preparation, structure, and properties of the materials were not fully disclosed (Scheme 52).218... 

This transformation proceeds through coordination of the isocyanide group to the ruthenium complex (structure 172), followed by insertion of the C-bound ruthenium into the benzylic C-H bond (intermediate 173). After ruthenium-mediated addition of the benzylic carbon to the isonitrile carbon and tautomerization, the desired product was obtained via elimination of the ruthenium complex. 

In many of its reactions hydrocyanic acid behaves as the nitrile of formic add H.CN. Many facts, in particular its great chemical and pharmacological similarity to the isonitriles >C = NR suggest another constitution, namely, that of carbimide >C =NH with bivalent carbon. The addition reactions of the nitriles (see above), which reactions are also characteristic of hydrocyanic acid, can equally well be explained on the basis of this second structural formula. In the nitrile form it is at the triple bond between carbon and nitrogen that addition takes place. In the methylene form this occurs at the two free valencies of the bivalent carbon atom, e.g. ... 

The structure of rhodium(II) carboxylate-derived carbene complexes has been assessed both by quantum mechanical calculations [19,20] and by the study of rhodium(II) carboxylate isonitrile complexes [20,21]. Recent investigations [20] suggest, that also in these highly electrophilic carbene complexes there is a significant n backbonding from rhodium to carbon. 

Isonitrile complexes, having a similar electronic structure to carbonyl complexes, can also react with nucleophiles. Amino-substituted carbene complexes can be prepared in this way (Figure 2.6) [109-112]. Complexes of acceptor-substituted isonitriles can undergo 1,3-dipolar cycloaddition reactions with aldehydes, electron-poor olefins [113], isocyanates [114,115], carbon disulfide [115], etc., to yield heterocycloalkylidene complexes (Figure 2.6). 

The structural diversity of natural products with antimalarial activity from marine and freshwater sources are stunning, ranging from isonitrile-containing derivatives to depsipeptides through peroxides and alkaloids. 

Iron(ii) complexes of ethylenedithiodiacetic acid, diethylenetrithioacetic acid, and ethylenetetrathiotetra-acetic acid have all been reported. " " Isonitrile and other complexes. Refluxing [Fe(CNMe) ](HSOj2 "hh excess methylamine for 12 h in methanol gives the cation [Fe(CNMe)gNH2Me] which can be precipitated as its PF salt. " The structure of this cation has been determined by X-ray methods and is shown in (52). The location of the protons was confirmed by n.m.r. and the suggested mechanism of formation is as shown. 

As shown in Fig. 17, multiple Ugi macrocyclizations using bifunctional isonitriles (MUMBIs) are an interesting form of MiBs, offering many possibilities for macrocyclization and structural variation. 

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