Preparation of an isocyano-beta-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 (C(2)O(4)(2-)) and HC(2)O(4)(-). 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)(H(2)O)(2), and two other intermediates are also reported.