Despite the high efficiency and broad scope of chiral iridium(N,P ligand) complexes as catalysts for asymmetric hydrogenation, the problem of catalyst recovery and recycling has so far attracted little attention. We have found that at the end of a hydrogenation reaction, iridium(N,P ligand) catalysts form dimeric Ir(III) dihydride complexes, which can be converted back to the original precatalysts by addition of COD. Based on these findings, a practically simple protocol for catalyst recovery was devised. The recovered complexes showed essentially the same reactivity and enantioselectivity as the original catalysts. Especially large‐scale applications and hydrogenations of less reactive substrates that require high catalyst loadings will benefit from this protocol that allows recovery and reuse of expensive iridium complexes.

中文翻译：

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从加氢反应中回收和回收手性铱（N，P配体）催化剂

尽管手性铱（N，P配体）配合物作为不对称氢化的催化剂具有很高的效率和广泛的应用范围，但迄今为止，催化剂的回收和再循环问题一直很少受到关注。我们发现，在氢化反应结束时，铱（N，P配体）催化剂形成二聚Ir（III）二氢化物络合物，可通过添加COD将其转化回原始的预催化剂。基于这些发现，设计了一种实际上简单的催化剂回收方案。回收的配合物显示出与原始催化剂基本相同的反应性和对映选择性。特别是大规模应用和需要高催化剂负载量的反应性较低的底物的氢化反应将受益于该协议，该协议可回收和再利用昂贵的铱配合物。