P-Tolyl isocyanide

Isocyanides, which are better candidates to react with dienes in a 1,4-fashion, were shown to cycloadd to 1-azadienes. Thus, the formation of isoindole derivative 15 as the major product (ca. 28% yield), upon treatment of benzoquinone 13 with two equivalents of p-tolyl isocyanide [81AG(E)982] was reported the reaction involves the insertion of the isocyanide carbon atom into the C—H bond of 13 leading to the 1-azadiene derivative 14, which in turn undergoes a [4 + 1] cycloaddition with a second isocyanide molecule (Scheme 4). 

A p-tolyl isocyanide complex of stoichiometry [Re02(PPh3)2(CNR)2]I has been reported312 but remains incompletely characterized. Other isocyanide-containing derivatives are unknown. 

Figure 8. Paramagnetic [Ir(L) (p-tolyl-isocyanide)(AsPh3)] complexes.

Two major series of carbene complexes have been investigated (a) those derived from co-ordinated p-tolyl isocyanide (Scheme 1) and (b) those derived from a trimeric complex of a a-bonded imidazole (Scheme 2). Mossabauer data for these materials are given in Table 4. 

C32H28Br3N, Re, Tribromo-tetra(p-tolyl isocyanide)rhenium, 45B, 888 C32H2sCoI2N4, Diiodotetrakis(p-tolylisocyano)cobalt(II), 40B, 1107 C32H28Fe2NOgP, M Diphenylphosphido-M (iminium-ion)-bis(tricarbonyl-iron), 44B, 722... 

Reactions of Co-ordinated Ligands. The topic of the attack of pyridine at co-ordinated ethene and co-ordinated dienes in appropriate platinum(ii) complexes has already been alluded to in an earlier section. " The reaction of c -[PtCl2(p-tolyl isocyanide) 2] with methylhydrazine in dichloromethane, which gives a carbene complex, follows a two-term rate law of this type shown in equation (1). As usual the term is assigned to a solvolytic path, but here the term is attributed to bimolecular attack of the hydrazine at the co-ordinated isocyanide. There is some discussion... 

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