Reactions of α-Diimine-Stabilized Zn–Zn-Bonded Compounds with Phenylacetylene

Treatment of the Zn–Zn-bonded compounds [L2–Zn–ZnL2–]·[M­(THF)2]2 (1a, M = Na; 1b, M
= K; L = [(2,6-iPr2C6H3)­NC­(Me)]2), which contain doubly reduced α-diimine
ligands, with 15-crown-5
and 18-crown-6 led to the ion-separated compounds [L2–Zn–ZnL2–]·[Na­(15-crown-5)­(THF)2]2 (2a), [L2–Zn–ZnL2–]·[K­(15-crown-5)2]2·4THF
(2b), and [L2–Zn–ZnL2–]·[K­(18-crown-6)­(THF)2]2·2THF (2c). In the products, the alkali metal ions originally bound
by the ligands have been captured by the crown ethers. The Zn–Zn
bond distances in 2a, 2b, and 2c are longer than those in the corresponding parent compounds 1a and 1b and in an analogous compound, [L–Zn–ZnL–] (3),
bearing the monoanionic α-diimine ligands. Theoretical computations
suggested that the Zn–Zn bonds in 2a–c are less stable than those in 1a and 1b. Reactions of [L–Zn–ZnL–] (3) with different amounts of PhCCH afforded
the dimeric product [L–Zn­(μ-CCPh)]2 (4) and the monomeric [L0Zn­(CCPh)2]·2THF (5), respectively, while the reaction
of the crown ether-containing compound 2b with PhCCH
gave a homoleptic zinc alkynide, [Zn­(CCPh)4]·[K­(15-crown-5)2]2·THF (6).

将含有双还原型α-二亚胺配体（α-diimine）的Zn-Zn键合化合物[L₂–Zn–ZnL₂⁻]·[M­(四氢呋喃(THF))₂]₂（1a，M = Na；1b，M = K；L = [(2,6-ⁱPr₂C₆H₃)­NC­(Me)]₂）分别与15-冠-5和18-冠-6反应，得到离子分离型化合物[L₂–Zn–ZnL₂⁻]·[Na­(15-冠-5)­(THF)₂]₂（2a）、[L₂–Zn–ZnL₂⁻]·[K­(15-冠-5)₂]₂·4THF（2b）与[L₂–Zn–ZnL₂⁻]·[K­(18-冠-6)­(THF)₂]₂·2THF（2c）。在上述产物中，原本与配体配位的碱金属离子被冠醚（crown ether）所捕获。2a、2b与2c中的Zn-Zn键长均长于对应母体化合物1a、1b，以及带有单阴离子型α-二亚胺配体的类似化合物[L–Zn–ZnL⁻]（3）中的Zn-Zn键长。理论计算表明，2a~2c中的Zn-Zn键稳定性弱于1a与1b中的Zn-Zn键。[L–Zn–ZnL⁻]（3）与不同当量的苯乙炔分别反应，得到二聚产物[L–Zn­(μ-C≡CPh)]₂（4）与单体产物[L⁰Zn­(C≡CPh)₂]·2THF（5）；而含冠醚的化合物2b与苯乙炔反应，则得到均配型炔锌配合物（homoleptic zinc alkynide）[Zn­(C≡CPh)₄]·[K­(15-冠-5)₂]₂·THF（6）。