Isonitrile complex

Divalent molybdenum compounds occur in mononuclear, dinuclear, and hexanuclear forms. Selected examples are shown in Figure 6. The mononuclear compounds are mostiy in the realm of organometaUic chemistry (30—32). Seven-coordinate complexes are common and include MoX2(CO)2(PR3)2, where X = Cl, Br, and I, and R = alkyl MoCl2(P(CH3)3)4, heptakis(isonitrile) complexes of the form Mo(CNR) 2 (Fig. 6d), and their chloro-substituted derivatives, eg, Mo(CNR)3CR. The latter undergo reductive coupling to form C—C bonds in the molybdenum coordination sphere (33). 

Malatesta, L., and Bonati, F., Isonitrile Complexes of Metals. Wiley, New York (1969). 

Kaharu, T., Ishii, R. and Takahashi, S. (1994) Liquid-crystalline gold—isonitrile complexes. Journal of the Chemical Society, Chemical Communications, (11), 1349-1350. 

Alejos, P., Coco, S. and Espinet, P. (1995) Liquid Crystals based on alkynylgold(I) isonitrile complexes. New Journal of Chemistry, 19, 799-805. 

Bayon, R., Coco, S., Espinet, P., Fernandez-Mayordomo, C. and Martm-Alvarez, J.M. (1997) Liquid Crystalline Mono and Dinudear Perhalophenylgold(I) Isonitrile Complexes. Inorganic Chemistry, 36, 2329-2334. 

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. 

Despite a common perception that organometallic chemistry essentially belongs in the province of catalysis rather than in vivo applications because of high reactivity of metal carbon bonds, certain organometallic species have very high kinetic stability. Indeed, this point is highlighted by the present wide application of the isonitrile complex Tc(ses-tamibi), [Tc(2-methoxyisobutylisonitrile)6]+, in myocardial imaging. Rhenium tricarbonyl and cyclopentadienyl complexes offer further ex-... 

Isomorphic monomers, 19 762 Isoniazid, 25 798 Isonicotinic hydrazide, 21 103 Isonitrile complexes, platinum, 19 656 Isonitrile-nitrile rearrangement, 21 149 Isononanoic acid, physical properties, 5 35t Isononyl alcohol, properties of commercial, 2 12t... 

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). 

Fig. 2.6. Preparation of aminocarbene complexes from isonitrile complexes (Z electron withdrawing group X=Y dipolarophile).

Multicomponent condensations have also been described in these an isonitrile, a carbonyl compound and a suitable transition metal complex are combined in one step to afford heterocycloalkylidene complexes. Examples of the use of isolated or intermediate isonitrile complexes for the preparation of aminocarbene complexes are given in Table 2.4. 

Table 2.4. Heteroatom-substituted carbene complexes prepared from isonitrile complexes.

Besides the addition of non-carbon nucleophiles to carbonyl and isonitrile complexes (Tables 2.2, 2.4), heteroatom-disubstituted carbene complexes can be prepared by direct addition of stable or latent carbenes to suitable complexes. The synthetic routes sketched in Figure 2.12 are those commonly used for preparing imidazoline-2-ylidene or imidazolidine-2-ylidene complexes. 

Isomer shift data, Fe,S4 clusters, 38 20, 50 Isomorphic substitution, 39 179, 186 p-Isonicotinamide complexes, osmium, 37 307 p-lsonicotinamidepoly(proline) complexes, osmium, 37 307 Isonitrile complexes osmium, 37 245 technetium(I), 41 13-14 technetium(II), 41 31 technetium(IIl), 41 45 Isopolymolybdates, 19 239ff 19 265-280 crystallization from aqueous solution, 19 265-269... 

Reactions of a Silylene-Isonitrile Complex as a Masked Silylene. 689... 

As mentioned above, there have been no examples of stable diarylsilylene although dialkyl- or diamino-substituted silylenes are now available as stable crystalline compounds. However, Tokitoh et al. found that the overcrowded diarylsilylene-isonitrile complexes 139 act as a free silylene 138 in solution even at room temperature. Since there is a severe limitation in a study concerning the reactivities of silylenes under the conventional generating conditions, the reactivity of silylene-isonitrile complexes 139 as a masked silylene is of great interest. 

Consequently, the reactivity of silylene-isonitrile complexes 139 as a masked silylene may provide us with not only a new and useful synthetic building block for a variety of organosUicon compounds but also a new research field in silylene chemistry. 

The product of Equation 41 is generally of the form RNC—AgX. A recent review of isonitrile complexes (53) reveals that all the entries in Table I form such species, and that all those not circled may be prepared by direct alkylation... 

Table I. Elements Forming Isonitrile Complexes by Direct Alkylation (53)...

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