Preparation of an Isocyano-β-diketone via its Metal Complexes, by Use of Metal Ions as Protecting Groups

A ligand containing isocyanide and beta-diketone functional groups, 3-(4-isocyanophenyl)-2,4-pentanedione (HacphNC), and several of its metal complexes have been prepared. The free isocyano-beta-diketone could not be prepared by dehydration of the analogous formamide, HacphNHCHO, because of the reactivity of its beta-diketone moiety. Instead, the metal complexes Al(acphNC)(3), Fe(acphNC)(3), Cu(acphNC)(2), and Zn(acphNC)(2) were synthesized by dehydration of the. formamido-beta-diketonate complexes Al(acphNHCHO)(3), Fe(acphNHCHO)(3), Cu-(acphNHCHO)(2), and Zn(acphNHCHO)(2). The free isocyano-beta-diketone, HacphNC, can be liberated from its Al and Fe complexes by treatment with oxalate (C2O42-) and HC2O4. In addition to these O-bound complexes, C(N)-bound complexes can be prepared by the reaction of either Al(acphNC)(3) or HacphNC with Au(I). X-ray analyses of HacphNC, Al(acphNC)(3), (HacphNC)AuCl, Cu(acphNHCHO)(2), trans-Zn(acphNHCHO)(2)(H2O)(2), and two other intermediates are also reported.