Ferrocenes are versatile ligand scaffolds, complexes of which have found numerous applications in catalysis. Structurally similar but of higher redox stabilites are sandwich complexes of the [Re(η6-arene)2]+ type. We report herein routes for conjugating potential ligands to a single or to both arenes in this scaffold. Since the arene rings can freely rotate, the [Re(η6-arene)2]+ has a high degree of structural flexibility. Polypyridyl ligands were successfully introduced. The coordination of Co(ii) to such a model tetrapyridyl-Re(i)-bis-benzene complex produced a bimetallic Re(i)-Co(ii) complex. To show the stability of the resulting architecture, a selected complex was subjected to photocatalytic reactions. It showed good activity in proton reduction over a long time and did not decompose, corroborating its extraordinary stability even under light irradiation. Its activity compares well with the parent catalyst in turn over numbers and frequencies. The supply of electrons limits catalytic turnover frequency at concentrations below ∼10 μM. We also show that other ligands can be introduced along these strategies. The great diversity offered by [Re(η6-arene)2]+ sandwich complexes from a synthetic point allows this concept to be extended to other catalytic processes, comparable to ferrocenes.

中文翻译：

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[Re（η6-芳烃）2] +作为配体和络合物的高度稳定的二茂铁状骨架。

二茂铁是通用的配体支架，其配合物在催化中已发现许多应用。结构相似但具有较高氧化还原稳定性的是[Re（η6-芳烃）2] +型夹心复合物。我们在此报告了在该支架中将潜在配体缀合至单个或两个芳烃的途径。由于芳烃环可以自由旋转，因此[Re（η6-芳烃）2] +具有高度的结构柔性。聚吡啶基配体已成功引入。Co（ii）与这种模型的四吡啶基-Re（i）-双苯配合物的配位产生了双金属Re（i）-Co（ii）配合物。为了显示所得体系结构的稳定性，将选择的配合物进行光催化反应。长期以来显示出良好的质子还原活性，并且没有分解，甚至在光照射下也证实了其非凡的稳定性。在数量和频率上，其活性与母体催化剂相当。电子的供应在浓度低于约10μM时限制了催化转换频率。我们还表明可以沿着这些策略引入其他配体。从合成的角度来看，[Re（η6-芳烃）2] +夹心复合物具有极大的多样性，使得该概念可以扩展到与二茂铁相当的其他催化过程。