Cyclic (alkyl)(amino)carbenes (cAACs) are the merely known ligand set being capable of stabilizing two-coordinate cobalt(0) complexes. While two complexes of the type [(R₂-cAAC)₂Co] [R₂-cAAC = 5,5-dialkyl-3,3-dimethyl-2-(2′,6′-diisopropylphenyl)pyrrolidine-1-ylidene, R = Me, Et] have been reported for years, little is known regarding their reactivity. In this Article, we present the investigation on the reactivity of [(Me₂-cAAC)₂Co] (2). Complex 2 can be synthesized in a high yield from the reaction of [(Me₂-cAAC)₂CoCl] (1) with MeLi. The interaction of 2 with 1 equiv of ArBr (Ar = phenyl, mesityl) or n-C₈H₁₇X (X = Br, Cl) in THF affords the corresponding cobalt(I) complex [(Me₂-cAAC)₂CoX] (X = Cl, 1; Br, 3). The formation of ArH and n-C₈H₁₈ in these reactions and the relatively high half-wave potential of [(Me₂-cAAC)₂Co]^0/1+ over that of [ArBr]^0/1+ indicate an inner-sphere electron-transfer character of the C–X bond cleavage reactions mediated by 2. The two-coordinate cobalt(I) complex [(Me₂-cAAC)₂Co][BAr^F₄] (4) has been synthesized from the reaction of 2 with [Cp₂Fe][BAr^F₄]. Complex 2 reacts with the diazo compounds (p-tolyl)₂CN₂ and DmpCHN₂ (Dmp = 2,6-dimesitylphenyl) to form [(Me₂-cAAC)Co((η⁶-p-tolyl)(p-tolyl)CNN(Me₂-cAAC))] (5) and [(Me₂-cAAC)₂Co(σ-NNCHDmp)] (6), respectively. The formation of the azine ligand in 5 indicates the reactivity of the Co–C(carbene) bond in 2. In addition, the reaction of 2 with 4 equiv of 2,6-dimethylphenyl isocyanide (XylNC) gives the ligand-substitution product [(Me₂-cAAC)Co(CNXyl)₃] (7) and a ketenimine Me₂-cAACCNXyl (8) in good yields, and the interaction of 2 with 3-hexyne yields a three-coordinate cobalt(0) complex bearing η²-alkyne ligand [(Me₂-cAAC)₂Co(η²-EtCCEt)] (9). The diversified reactivity of 2 arises from the coordination–unsaturation and electron-rich (d⁹) nature of the cobalt center and demonstrates the promising synthetic utility of cobalt(0) cAAC complexes.

中文翻译：

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二坐标钴（0）环状（烷基）（氨基）卡宾配合物的反应性

环状（烷基）（氨基）卡宾（cAAC）是唯一已知的能够稳定两坐标钴（0）配合物的配体。而[[R ₂ -cAAC）₂ Co]型的两个络合物[R ₂ -cAAC = 5,5-二烷基-3,3-二甲基-2-（2'，6'-二异丙基苯基）吡咯烷-1-亚烷基[R = Me，Et]已有多年报道，对其反应性知之甚少。在本文中，我们对[（Me ₂ -cAAC）₂ Co]（2）的反应性进行了研究。[[Me ₂ -cAAC）₂ CoCl]（1）与MeLi的反应可以高产率地合成配合物2。互动2在THF中含有1当量的ArBr（Ar =苯基，异丁烯基）或n -C ₈ H ₁₇ X（X = Br，Cl）可得到相应的钴（I）络合物[（Me ₂ -cAAC）₂ CoX]（X = Cl，1； Br，3）。这些反应中ArH和n -C ₈ H ₁₈的形成以及[（Me ₂ -cAAC）₂ Co] ^{0/1 +}相对于[ArBr] ^{0/1 +}相对较高的半波电势表明内部2介导的C–X键断裂反应的非球形电子传递特性。二坐标钴（I）络合物[（Me₂ -cAAC）₂ CO] [巴^˚F ₄ ]（4）已经从反应合成2用的[Cp ₂的Fe] [巴^˚F ₄ ]。复杂2种发生反应与重氮化合物（p -甲苯基）₂ CN ₂和DmpCHN ₂（DMP = 2,6- dimesitylphenyl），以形成[（ME ₂ -cAAC）钴（（η ⁶ - p -甲苯基）（p -甲苯基）CNN（Me ₂ -cAAC））]（5）和[（Me ₂ -cAAC）₂ Co（σ-NNCHDmp）]（6）， 分别。在吖嗪配体的形成5表示在CO-C（碳烯）键的反应性2。此外，2与4当量的2,6-二甲基苯基异氰化物（XylNC）的反应生成配体取代产物[（Me ₂ -cAAC）Co（CNXyl）₃ ]（7）和一个烯酮胺Me ₂ -cAACCNXyl（8）以良好的收率，和的相互作用2与3-己炔产生三维坐标钴（0）络合物轴承η ² -alkyne配体[（ME ₂ -cAAC）₂的Co（η ² -EtCCEt）]（9）。的多样化反应2产生于协调不饱和度和富电子（d ⁹的钴中心）性质和演示钴（0）配合物CAAC的有前途的合成工具。