Neutral Organometallic Palladium(II) Aquo Complexes

The reactions of chlorobridged cyclometalated complexes [Pd(C−N)(μ-Cl)] 2 (C−N = orthometalated N,N -dimethylbenzylamine, dmba; 2-( para -tolyl)pyridine, p -tolpy; azobenzene, azb; N,N -dimethyl-1-naphthylamine, dmna; and 2-benzylpyridine, bzpy) with Li(Fmes) (Fmes = 2,4,6-tris(trifluoromethyl)phenyl or nonafluoromesityl) give, after hydrolysis, neutral aquo complexes [Pd(C−N)(Fmes)(OH 2 )], where the ipso carbon atoms of the Fmes and the cyclometalated ligand are coordinated cis, as shown by an X-ray diffraction study of [Pd(dmba)(Fmes)(OH 2 )]. The aquo ligand is readily displaced by other ligands, giving complexes [Pd(C−N)(Fmes)L] (L = PPh 3, 2,6-lutidine, NH 3, CN t Bu, CO) when monodentate ligands are employed or [Pd(dmba- C )(Fmes)(2,2‘-bipy)], which contains a chelating 2,2‘-bipyridyl and a monodentate C-bonded dmba. Different processes in solution are detected for the complexes containing the bulkier ligands: ligand rotation in the complex with PPh 3; inversion of the bipy ligand in [Pd(dmba- C )(Fmes)(2,2‘-bipy)]; and equilibria with residual water in the solutions of [Pd(C−N)(Fmes)(lut)] and [Pd(dmba- C )(Fmes)(2,2‘-bipy)].