Palladium(II) complexes with the cyclometalated C-Y-N(sp2)-Pd-C(sp2) ring (Y = N, C) and (R)-(+)- hydroxymethylenecamphor

The reactions between the cyclopalladated chloro-dimers [Pd(Ln)(μ-Cl)2] (HL1 = 2,6-dimethylazobenzene, HL2 = 4,4′-dimethoxyazobenzene, HL3 = 4-ethoxy-4′-heptanoylazobenzene, HL4 = 5-(1-hexyl)-2-[4′-(1-undecyloxy)phenyl]pyrimidine) and the optically pure K[(R)-(+)-MC] salt ((R)-(+)-MC =(R)-(+)-bicyclo[2,2,1]-heptan-2-onate-3-(hydroxymethylene)-1,7,7′-trimethyl) give the corresponding mononuclear Pd(Ln)[(R)-(+)-MC] complexes 1-4. NMR and circular dichroism data account for diastereoisomeric mixtures which consist of two complexes differing in the 7,7′ dimethyl bridge being above or below the palladium coordination plane. The relative abundance of diastereoisomers has been estimated by NMR spectroscopy.