Amido PNP pincer complexes of palladium(II) and platinum(II): Synthesis, structure, and reactivity

The synthesis of a series of divalent palladium and platinum complexes containing amido PNP pincer ligands of the type [N(o-C6H4PR2)(2)](-) (R = Ph (1a), iPr (1b)) is reported. Metathetical reactions of [1a-b]PdCl or [1a-b]PtCl with a variety of alkyl Grignard reagents or LiHBEt3 in ethereal or arene solutions generate their corresponding alkyl or hydride complexes [1a]PdR1 (R-1 = Me, Et, nBu), [1b]PdR1 (R-1 = Me, Et, H), [1a]PtR1 (R-1 = Me, Et, nBu, nHexyl, H), and [1b]PtR1 (R-1 = Me, H). Although these organometallic complexes are all thermally stable, including those containing beta-hydrogen atoms even at elevated temperatures, compounds [1a]PdH and [1b]PtR1 (R-1 = Et, nBu, nHexyl) are not isolable due to facile decomposition. The stability and reactivity of these complexes are discussed. The chloro [1a]PdCl is a superior catalyst precursor to [1b]PdCl, [1a]PtCl, and [1b]PtCl in Kumada couplings, affording, for instance, n-butyl arenes nearly quantitatively. The X-ray structures of [1b]PtCl, [1b]PtMe, [1b]PdEt, [1a]PtnBu, [1b]PdH, and [1b]PtH are presented.