Isocyanides cleavage

We present at the end of this section, several isolated examples of trinuclear cyanide-bridged complexes that do not fall within the two major classes of compounds. The first group of such complexes is based on a triangular cluster core. For example, Evans et al., (127) obtained [(Cp )2Sm CNR)( j,-CN)]3 (R = hexyl, tert-butyl) [Fig. 19(a)] from a reductive cleavage of the isocyanide CNR ligand by Cp 2Sm (thf)2. Moreover, the same group later demonstrated the preparation of such trinuclear complexes by isocyanide cleavage with Cp 3Sm ... 

Convincing evidence for the intermediacy of an isocyanide cleavage product in the N2-C3 interchange transposition was obtained by studying the photochemistry of 4-benzylisothiazole 21... 

Salicylonitrile is believed to arise by direct cleavage with subsequent hydrogen transfer, while the benzoxazoles were produced by an isocyanide intermediate (73JA919, 74HCA376). Photolysis in D2O tends to confirm this possibility and rule out an azirine intermediate (39), due to deuterium corporation into the molecule (Scheme 10) (74HCA376). 

The easy cleavage by reduction of the N—C bond in isocyanides, which was recently observed by I. Ugi and F. Bodesheim [Chem. Ber. 94, 1167 (1961)], stimulated this experiment. 

Conversion of epoxides into /3-hydroxy isocyanides—preparation of trans-2-isocyanocyclohexanol, using TMSCN to open cyclohexene oxide with trans stereochemistry, followed by KF/MeOH cleavage of the intermediate silyl ether. 

The reaction of [p-MeC6H4C(NSiMe3)2]2Ta( = CH2)CH3 with 2,6-dimethyl-phenyl isocyanide afforded an f/ -ketenimine complex (Scheme 118). Carbon-sulfur cleavage reactions produced tantalum thioformaldehyde and tantalum sulfido complexes. ... 

The hexakis(methyl isocyanide) dimers, [Pt2(CNMe)6], undergo photolytic cleavage of the Pt—Pt bond to give 15-electron radicals, Pt(CNMe)3.94 Mixtures of platinum and palladium dimers give rise to heteronuclear complexes under photolytic conditions. Mixtures of normal and deuterium-labeled methyl isocyanide complexes reveal that the metal-ligand bonds undergo thermal redistribution.94... 

The reaction of OsHCl(CO)(P Pr3)2 with HC1 gives the dichloro derivative OsCl2( n2-H2)(CO)(PIPr3)2.35 In solution, this complex is stable under argon for a matter of days. However, the dihydrogen unit is highly activated toward heterolytic cleavage, as demonstrated by deprotonation with NaH and by reactions with carbon monoxide and /ert-butyl isocyanide, which afford OsHCl(CO)L(P Pr3)2 (L = CO, r-BuNC) and HC1. 

Bis-silylation of bicyclopropylidene in the presence of the palladium-isocyanide catalyst with hexamethyldisilane and phenylpentamethyldisilane gives 1,2-addition products in good yields at 70 °C vide supra). No G-G bond cleavage takes place with the bis-silylation reaction. In contrast to this example, in which both the cyclopropane rings are... 

Silaboration of bicyclopropylidene proceeds via proximal G-G bond cleavage at 130 °C in the presence of the palladium// r/-alkyl isocyanide catalyst (Equation (88)). In contrast to the aforementioned silaboration of methylene cyclopropanes, vinylsilane products are obtained with high regioselectivity.102... 

The only carbene-like reaction reported so far is the low-temperature addition of tert-butyl isocyanide to carbenes 2d and 2u.78 From the P-hydrogenophosphonio carbene 2d, the heterocycle 89 was isolated in high yield. It is believed that the initial coupling product 87d rapidly inserts a further equivalent of isocyanide into the P-H bond, leading to the intermediate 88, which then undergoes rapid elimination of diisopropylamine. When the same reaction was performed with the P-chloro(phosphonio)car-bene 2u, a 1/1 mixture of keteneimine 90 and phosphinonitrile was obtained. This result can be explained by the cleavage of the carbene-isocyanide coupling product 87u by residual HCN, inherently present in the f-BuNC. 

Irradiation of [Re(CNC6Fl3-2,6-Me2)6] with UV light in CH2CI2 in the presence of halide ions yields complexes of the type [Re(CNCgH3-2,6-Me2)5X] (X = Cl, Br, or I). The quantum yield of this reaction is high and results in chemical yields between 30% and 40%. Products of the same composition have been obtained directly from the cleavage of the metal-metal bond in quadruply bonded rhenium complexes of various compositions in the presence of isocyanides. ... 

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