Formation and Subsequent Reactivity of a N₂‑Stabilized Cobalt–Hydride Complex

The reduced heterobimetallic Co/Zr complex N2Co­(iPr2PNMes)3Zr­(THF) (1) has been previously reported to react with the CO bonds of CO2 and benzophenone to generate Zr/Co μ-oxo complexes OC-Co­(iPr2PNMes)2(μ-O)­Zr­(iPr2PNMes) (1-CO2) and Ph2CCo­(iPr2PNMes)2(μ-O)­Zr­(iPr2PNMes) (1-Ph2CO), respectively. Herein, we report a similar reaction of 1 with pyridine-N-oxide to form an analogous complex (pyridine)­Co­(iPr2PNMes)2(μ-O)­Zr­(iPr2PNMes) (2) with a more labile ligand bound to cobalt. Much like 1-CO2 and 1-Ph2CO, compound 2 reacts with Ph3SiH via formation of a Si–O linkage to form (N2)­(H)­Co­(iPr2PNMes)3ZrOSiPh3 (5). The dinitrogen ligand in 5 is weakly bound and can be readily removed in vacuo or displaced by other L-type ligands. This allows complex 5 to undergo insertion reactions with unsaturated substrates, including diphenyldiazomethane, CO2, benzonitrile, and phenylacetylene to give hydrazonato (Ph2CNNH)­Co­(iPr2PNMes)3ZrOSiPh3 (7), formate (OC­(H)­O)­Co­(iPr2PNMes)3ZrOSiPh3 (8), ketimide (PhHCN)­Co­(iPr2PNMes)3ZrOSiPh3 (9), and ylide Co­(PhHCCHPiPr2NMes)­(iPr2PNMes)2ZrOSiPh3 (10) products, respectively. Compound 5 was also found to catalyze the isomerization of 1-hexene to internal isomers.此前已有报道称，还原型异双金属钴/锆（Co/Zr）配合物N₂Co(iPr₂PNMes)₃Zr(THF)（记为1）可与二氧化碳（CO₂）和二苯甲酮的碳氧双键（C=O）发生反应，分别生成锆/钴型μ-氧桥配合物OC-Co(iPr₂PNMes)₂(μ-O)Zr(iPr₂PNMes)（1-CO₂）以及Ph₂C=Co(iPr₂PNMes)₂(μ-O)Zr(iPr₂PNMes)（1-Ph₂CO）。本文中，我们报道了配合物1与吡啶-N-氧化物的类似反应，该反应可生成结构相似的配合物(pyridine)Co(iPr₂PNMes)₂(μ-O)Zr(iPr₂PNMes)（记为2），其钴中心结合的配体更易解离。与1-CO₂和1-Ph₂CO类似，化合物2可与三苯基硅烷（Ph₃SiH）发生反应，通过形成硅氧键（Si-O）生成配合物(N₂)(H)Co(iPr₂PNMes)₃ZrOSiPh₃（记为5）。配合物5中的二氮配体结合较弱，可在真空条件下轻易脱除，或被其他L型配体（L-type ligands）取代。这使得配合物5可与多种不饱和底物发生插入反应，包括二苯基重氮甲烷、二氧化碳（CO₂）、苯甲腈以及苯乙炔，分别得到腙基配体型（hydrazonato）产物(Ph₂C=NNH)Co(iPr₂PNMes)₃ZrOSiPh₃（记为7）、甲酸根配体型（formate）产物(OC(H)O)Co(iPr₂PNMes)₃ZrOSiPh₃（记为8）、酮亚胺基配体型（ketimide）产物(PhHC=N)Co(iPr₂PNMes)₃ZrOSiPh₃（记为9）以及叶立德型（ylide）产物Co(PhHC=CHPiPr₂NMes)(iPr₂PNMes)₂ZrOSiPh₃（记为10）。此外，我们还发现配合物5可催化1-己烯异构为内部烯烃异构体。