CJC｜Cornerstones in Chemistry：共轭碳链螯合过渡金属构筑多个金属-碳键

Construction of Multiple M–C Bonds: Chelation with Conjugated Carbon Chains

Xiaoxi Zhou, Qingde Zhuo*

The formation of metal–carbon (M–C) bonds represents a fundamental process in organometallic chemistry. A central question arises: what is the maximum number of M–C bonds that can be formed on a single metal center? Over the past decade, Xia and co-workers have been dedicated to addressing this challenge. They developed a strategy based on chelating metal centers with conjugated carbon chains, which allows for the formation of multiple M–C bonds whose number increases with the length of the carbon chain. A landmark achievement came in 2013 with the first synthesis of metallapentalynes, a new class of metal-bridged fused-ring metallacycles with planar Craig aromaticity. These complexes are formally constructed by chelating a metal center with a seven- atom conjugated carbon ligand via three M–C σ bonds. This breakthrough established a new research area termed “carbolong chemistry”, which focuses on the interactions between transition metals and conjugated carbon ligands. Since then, the Xia group has synthesized a diverse family of carbon-based polydentate chelates involving three to five coplanar M–C σ bonds, including the first metal-centered [15]annulene, collectively known as “carbolong complexes”. Moreover, carbolong motifs have been successfully incorporated into polymer backbones, yielding a new class of materials with numerous M–C bonds, referred to as “polycarbolongs”. Both carbolong complexes and polycarbolongs exhibit not only unique structures but also remarkable properties, showing considerable potential in applications such as catalysis, biomedicine, luminescent materials, and photovoltaics. This review summarizes recent advances in the synthesis and applications of carbolong complexes and polycarbolongs.

Metal–carbon bond | Conjugated carbon chain | Carbolong chemistry | Polydentate chelate | Aromaticity | Alkynes | Cycloaddition |

Metallacycles

       金属-碳键的构筑是金属有机化学的核心。从首个过渡金属有机化合物——蔡斯盐的发现，到二茂铁引发的成键理论革命，再到获得诺贝尔化学奖的烯烃复分解反应突破，这些里程碑成果的取得都与金属-碳键构筑技术的发展紧切相关。如今，含金属‑碳键的化合物已在催化、材料科学等诸多领域发挥着重要作用。

      传统研究多集中于单齿碳配体配位的金属有机化合物，如金属烷基、金属羰基及金属卡宾化合物等。相比之下，含有多个金属‑碳键的多齿螯合物仍较为罕见。在配位化学中，氮、氧、磷、硫等杂原子长期占据配位主导地位，碳原子往往只能作为辅助配位原子。因此，发展含多个金属‑碳键的新型多齿螯合物，成为金属有机化学与配位化学共同面临的重要挑战。

      夏海平院士团队近年来在金属‑碳键构筑领域开展了系统、深入研究，原创性地发展了利用共轭碳链螯合过渡金属构筑金属‑碳键的新方法，开创了“碳龙化学”这一全新方向。团队发现，金属‑碳键的数目可随共轭碳链的增长而逐步增加。基于这一原创策略，他们成功构建了一系列结构新颖的分子骨架基元——碳龙配合物。该类配合物由一条平面共轭碳链（碳数≥7）通过至少三个碳‑金属σ键螯合过渡金属中心，形成独特的dπ‑pπ共轭体系。此外，团队还将该策略拓展至高分子合成领域，制备出具有海量金属‑碳键的新型共轭高分子——聚碳龙。碳龙配合物与聚碳龙不仅结构独特，还展现出优异的光、电性能，在均相催化、太阳能电池、生物医学等多个前沿领域显示出巨大的应用潜力。

      本综述系统阐述了碳龙化学的发展脉络，重点聚焦碳龙配合物及聚碳龙的合成策略与应用进展。本文作为Cornerstones in Chemistry发表于Chin. J. Chem. (2026, 44, 583—603. DOI: 10.1002/cjoc.70412)。该项工作得到了中国科学技术大学提供的基金资助。