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.

将(DIPP-nacnac)（定义为CH{(CMe)(2,6-iPr₂C₆H₃N)}₂，即CH{(C(CH₃))(2,6-二异丙基苯胺基)}₂）配位的双(三甲基硅基（SiMe3）)氨基钙配合物溶剂合物(DIPP-nacnac)Ca[N(SiMe₃)₂]·四氢呋喃（THF）与氨气（NH₃）反应，得到杂配体配合物(DIPP-nacnac)CaNH₂·(NH₃)₂。该配合物以二聚体形式结晶，氨基阴离子（NH₂⁻）作为桥联配体。与其他(DIPP-nacnac)配位的钙酰胺杂配体配合物相比，(DIPP-nacnac)CaNH₂·(NH₃)₂对配体交换反应具有显著的稳定性。
将溶剂化于四氢呋喃（THF）的(DIPP-nacnac)氢化钙配合物(DIPP-nacnac)CaH·THF与三甲基硅基氰（Me₃SiCN）反应，得到杂配体配合物(DIPP-nacnac)CaCN·THF。该配合物以三聚体形式结晶，氰根阴离子（CN⁻）以线性方式桥联钙离子（Ca²+）。
采用新型合成路径，(DIPP-nacnac)Ca[N(SiMe₃)₂]·THF与三乙基氯化铵（Et₃NH⁺Cl⁻）反应，得到(DIPP-nacnac)CaCl·THF。该配合物以二聚体形式结晶，氯离子（Cl⁻）作为桥联配体。
这类聚集体对配体交换反应具有极高的稳定性——配体交换反应会生成不溶性的同配体配合物Ca(NH₂)₂、Ca(CN)₂或CaCl₂，这一特性十分引人注目，其原因大概率在于它们的多核结构特征。