A RIGID TRANS-SPANNING DINITRILE LIGAND

A rigid dinitrile ligand was synthesized from two xanthene units conde nsed to a naphthalene-1,4,5,8-diimide spacer. The rigidity acid C shap e of the ligand gave exclusively trans complexes with Pd(II), Ag(I), a nd Au(I). Evidence for complexation, coordination geometry, and stoich iometry was provided by a combination of H-1 NMR, F-19 NMR, and IR spe ctroscopy. The AuBF4 and PdCl2 complexes were shown to have a 1:1 (met al-to-ligand) stoichiometry and the AgBF4 complex was shown to have a 1:2 stoichiometry in solution. The preorganization of the dinitrile li gand resulted in complexes much more stable than their monodentate cou nterparts.