Reactions of cyclopalladated compounds. Part 24. Reactivity of the Pd–C bond of cyclopalladated compounds towards isocyanides and carbon monoxide. Role of the donor group

The Pd–C bond of a series of Cyclopalladated compounds of general formula [P[graphic omitted]Me)2(µ-Cl)2], obtained through direct palladation of thioether ligands, is remarkably reactive towards insertion of one isocyanide as compared to the corresponding compounds in which the SMe unit has been replaced by a NMe2 moiety. The most reactive compound of the series is that derived from orthopalladation of benzyl methyl thioether, which leads either to chloride-bridged dimers with benzyl- or phenyl-isocyanide or to imino-bridged dimers with t-butyl isocyanide. With the other cyclopalladated compounds, insertion of the isocyanides also takes place in the presence of 2 equivalents of isocyanides per palladium atom though less readily as in the previous case, affording new imino units σ-bonded to palladium via their imino carbon atom. Carbon monoxide is readily inserted into the Pd-C bond of most of these cyclopalladated compounds to afford new palladated acyl groups, this reaction being reversible.