Big Ligands for Stabilization of Small Functionalities in Calcium Chemistry

Reaction of (DIPP-nacnac)CaN(SiMe3)2·THF (DIPP-nacnac = CH{(CMe)(2,6-iPr2C6H3N)}2) with NH3 gave the heteroleptic complex (DIPP-nacnac)CaNH2·(NH3)2 which crystallized as a dimer with bridging NH2- ions. In contrast to other heteroleptic (DIPP-nacnac)calcium amides, (DIPP-nacnac)CaNH2·(NH3)2 is remarkably stable toward ligand exchange. Reaction of (DIPP-nacnac)CaH·THF with Me3SiCN gave the heteroleptic complex (DIPP-nacnac)CaCN·THF that crystallized as a trimer. The CN- ions bridge in a linear fashion between the Ca2+ ions. In a new synthetic route (DIPP-nacnac)CaN(SiMe3)2·THF reacted with Et3NH+Cl- to give (DIPP-nacnac)CaCl·THF, which crystallized as a dimer with bridging Cl- ions. The exceptional stability of these aggregates toward ligand-exchange reactions, which would give insoluble homoleptic Ca(NH2)2, Ca(CN)2, or CaCl2, is remarkable and likely due to their multinuclear nature.