Reactions of a Cationic Geminal Zr⁺/P Pair with Small Molecules

The metallocene cation complex [Cp*2ZrCH3]+[B­(C6F5)4]− inserts the phosphino-substituted alkyne Ph–CC–PPh2 into the [Zr]-CH3 bond to form the internally phosphane-stabilized cation [Cp*2Zr–C­(CMePh)­PPh2]+ (10). Complex 10 adds alkyl isocyanides as well as pivalonitrile at a lateral site at the bent metallocene wedge with retention of the Zr–P bond. Complex 10 acts as a reactive frustrated Lewis pair toward heterocumulenes, undergoing Zr+/P addition reactions to the carbonyl groups of an alkyl isocyanate and of carbon dioxide to form the respective five-membered metallaheterocyclic adducts 13 and 14. With mesityl azide complex 10 undergoes a Zr+/P FLP N,N-addition reaction at the terminal azide nitrogen atom to form the four-membered FLP cycloadduct 15. The Zr+/P FLP is a reactive hydrogen activator. In a stoichiometric reaction it generates a hydridozirconocene cation that subsequently serves as a hydrogenation catalyst for various olefinic or acetylenic substrates. The Zr+/P pair 10 undergoes selective 1,4-addition reactions to conjugated enones and to a conjugated ynone to give the corresponding seven-membered metallacyclic Zr+/P FLP addition products. Many compounds of this study were characterized by X-ray diffraction.茂金属阳离子配合物[Cp*2ZrCH3]+[B(C6F5)4]−将膦取代炔烃Ph–C≡C–PPh2插入至[Zr]-CH3键中，得到内部膦稳定化阳离子[Cp*2Zr–C(=CMePh)PPh2]+（标记为10）。配合物10可在弯曲型茂金属楔状结构的侧向位点结合烷基异氰与特戊腈，且反应过程中保留Zr–P键。配合物10可作为活性受阻路易斯对（frustrated Lewis pair, FLP）与杂累积烯烃反应：其Zr+/P位点可分别与烷基异氰酸酯及二氧化碳的羰基发生加成反应，生成对应的五元金属杂环加合物13与14。在与均三甲苯基叠氮的反应中，配合物10通过Zr+/P FLP的N,N-加成反应作用于叠氮末端氮原子，得到四元FLP环加合物15。该Zr+/P FLP是活性氢活化剂，在计量反应中可生成氢化茂锆阳离子，该阳离子随后可作为氢化催化剂用于各类烯烃或炔烃底物的氢化反应。配合物10可与共轭烯酮及共轭炔酮发生选择性1,4-加成反应，得到对应的七元金属环Zr+/P FLP加成产物。本研究中的多数化合物均通过X射线衍射完成结构表征。