Attempts to prepare palladium(II) complexes with the O,C,O pincer aryl ligand C-6(NO2)(2)-2,6-(OMe)(3)-3,4,5

The complex [HgR2] (R =C-6(NO2)(2)-2,6-(OMe)(3)-3,4,5-C-1 (2)), obtained by thermal decomposition of [Hg(O2CR)(2)] (1), reacts with Q(2)[Pd2Cl4(mu-Cl) (2)] to give [Hg(R)Cl] (3) and Q(2)[Pd(R)Cl(mu-Cl)](2) (Q = (PhCH2)Ph3P (4a ), Me4N (4b)), which react (i) with Tl(acac) (1:2, acac = acetylacetonate) to give Q[Pd(R)Cl(O,O-acac)] (Q = (PhCH2)Ph3P (5a), Me4N (5b)) or (ii) with AgClO4 (1:2) to give [Pd(kappa(3)-R)Cl] (kappa(3)-R = kappa(3)-C-6(NO2)(2) -2,6-(OMe)(3)-3,4,5-C-1, O,O' (6)), which can also be obtained by reacting 5a with HBF4. Complex 6 reacts with p-toluidine (1:1, L) to give [Pd(R)(mu- Cl)L](2) (7). Complex 5b decomposes in a mixture of acetone/water to give [ Pd(kappa(2)-R)(O,O-acac)] (kappa(2)-R = kappa(2)-C-6(NO2)(2)-2,6-(OMe)(3)-3 ,4,5-C-1,O (8)), which reads (i) with neutral monodentate ligands to give [ Pd(R)(O,O-acac)L] (L = PPh3 (9), pyridine (py) (10), tetrahydrothiophene (1 1)), (ii) with bis(diphenylphosphino)methane (dppm) to give a complex that readily oxidizes to give [Pd(R)(O,O-acac)(dppmO)] (dppmO = monoxide of bis( diphenylphosphino)methane (12)), (iii) with 1,10-phenanthroline (phen) to g ive [Pd(R)(C-acac)(phen)] (13), and (iv) with protonated ligands (HL)ClO4 t o give 10 (L = py) or cis-[Pd(R)(H2O)(2)(PPh3)]. H2O (L = PPh3 (14)). Trifl uoromethanesulfonic acid (HOSO2CF3) reacts with 9 and PPh3 or with 13 to gi ve trans-[Pd(R)(OSO2CF3)(PPh3)(2)] (15) or [Pd(R)(OSO2CF3)(phen)] (16), res pectively. The X-ray crystal structures of 7 . 2CH(2)Cl(2), 8, 10, and 14 . H2O have been determined.