Polymetalated aromatic compounds. 1. Synthesis of mono-, di-, and tripalladated mesitylene derivatives

The reaction of 1,3,5-triiodomesitylene (C6Me3I3) with a mixture of [Pd(dba )(2)] and PR3 leads to the mononuclear complexes trans- [Pd(C6Me3I2)I(PR3)( 2)] (R = Ph (1), R-3 = Me2Ph (2)) or the dinuclear complex [{trans-PdI(PMe2 Ph)(2)}(2)(mu (2)-C6Me3I)I (3), depending on the nature of the phosphine, t he temperature, and the molar ratio of the reagents. AE attempts to prepare trinuclear complexes, using this method of synthesis, were unsuccessful. H owever, addition of C6Me3I3 to a mixture of [Pd(dba)(2)] and L-2 gives at r oom temperature [(PdIL2)(3)-(mu (3)-C6Me3)] (L-2 = 2,2'-bipyridine (bpy) (4 ), 4,4'-di-tert-butyl-2,2'-bipiridine (tbbpy) (5)), even if substoichiometr ic amounts of Pd were used. Complex 5 does not react with PPh3 or PMe2-Ph, but it does react with PMe3 to give [trans-{PdI(PMe3)(2)}(3)(mu (3)-C6Me3)] . (6). The crystal structures of 1, 2, and 5 have been determined by X-ray diffraction studies.