Mono- and Bimetallic (NacNac)Ni Cyclopentadienyl Complexes^†

Complexes of the form (Nacnac)Ni(η5-L) (L = Cp (3), indenyl (4)) are readily prepared and have been protonated to generate the corresponding cationic species [(HNacNac)Ni(η5-L)][B(C6F5)4] (L = Cp (5), indenyl (6)). While the symmetric compound 3 is paramagnetic, disruption of the symmetry in 4−6 results in diamagnetism. The species [((Nacnac)Ni)2(μ-η5:η5-Cp)][B(C6F5)4] (7) was prepared in an unusual fashion from the reaction of [(NacNac)Ni]2(η6:η6-C6H5Me) (2) with [Ph3C][B(C6F5)4] and Cp2ZrMe2, while compound 3 serves as a synthon to the neutral bimetallic Ni(II)/Ni(I) species [((Nacnac)Ni)2(μ-η2:η2-Cp)] (8). Compounds 7 and 8 are readily interconverted electrochemically. Consideration of the molecular orbitals reveals that the unpaired electron in 8 prompts alteration of the nature of the bridging cyclopentadienyl ligand between the metal centers. Crystal structures of 3−5, 7, and 8 are reported.通式为(Nacnac)Ni(η⁵-L)的配合物（其中L为环戊二烯基(Cp)（化合物3）、茚基(indenyl)（化合物4））可简便制备，经质子化反应可得到对应的阳离子物种[(HNacNac)Ni(η⁵-L)][B(C₆F₅)₄]（L为Cp（化合物5）、茚基（化合物6））。对称化合物3具有顺磁性（paramagnetic），而化合物4~6因对称性被破坏，呈现反磁性（diamagnetic）。物种[((Nacnac)Ni)₂(μ-η⁵:η⁵-Cp)][B(C₆F₅)₄]（化合物7）以非常规方式合成：由[(Nacnac)Ni]₂(η⁶:η⁶-C₆H₅Me)（化合物2）与[Ph₃C][B(C₆F₅)₄]以及二甲基二茂锆(Cp₂ZrMe₂)反应制得；化合物3可作为合成子，用于制备中性双金属Ni(II)/Ni(I)物种[((Nacnac)Ni)₂(μ-η²:η²-Cp)]（化合物8）。化合物7与8可通过电化学手段实现相互转化。对分子轨道（molecular orbitals）的分析表明，化合物8中的未成对电子会使桥联环戊二烯配体在金属中心间的配位特性发生改变。本研究报道了化合物3~5、7及8的晶体结构。