<p>Monocyclic π-aromatic compounds are ubiquitous throughout almost all fields of natural sciences—as synthons in industrial processes, as ligands of metal complexes for catalysis or sensing and as bioactive molecules. Planar organocycles stand out through their specific way of overcoming electron deficiency by a non-localizable set of (4<i>n</i> + 2)π electrons. By contrast, all-metal aromatic monocycles are still rare, as metal atoms prefer to form clusters with multiply bonded atoms instead. This limits the knowledge and potential of corresponding compounds in chemical syntheses or for innovative materials. Here we report the successful generation of Bi<sub>5</sub><sup>−</sup>, the heaviest analogue of (C<sub>5</sub>H<sub>5</sub>)<sup>−</sup>. Its use as a ligand in [{IMesCo}<sub>2</sub>(µ,η<sup>5</sup>:η<sup>5</sup>-Bi<sub>5</sub>)] (1) was realized by reacting (TlBi<sub>3</sub>)<sup>2−</sup> with [(IMes)<sub>2</sub>CoCl] (where IMes is bis(1,3-(2,4,6-trimethylphenyl))imidazol-2-ylidene) in <i>ortho-</i>difluorobenzene. Compound 1 is mixed-valence Co<sup>0</sup>/Co<sup>I</sup> as verified by µ-SQUID measurements and density functional theory, and embeds the planar Bi<sub>5</sub><sup>−</sup> cycle in an inverse-sandwich-type manner. Capturing Bi<sub>5</sub><sup>−</sup> represents a landmark in the chemistry of all-metal aromatic molecules and defines a new era for aromatic compounds.</p><p></p>

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Isolation of a planar π-aromatic Bi5 ring in a cobalt-based inverse-sandwich-type complex

  • Julia Rienmüller,
  • Benjamin Peerless,
  • Sagar Paul,
  • Florian Bruder,
  • Wolfgang Wernsdorfer,
  • Florian Weigend,
  • Stefanie Dehnen

摘要

Monocyclic π-aromatic compounds are ubiquitous throughout almost all fields of natural sciences—as synthons in industrial processes, as ligands of metal complexes for catalysis or sensing and as bioactive molecules. Planar organocycles stand out through their specific way of overcoming electron deficiency by a non-localizable set of (4n + 2)π electrons. By contrast, all-metal aromatic monocycles are still rare, as metal atoms prefer to form clusters with multiply bonded atoms instead. This limits the knowledge and potential of corresponding compounds in chemical syntheses or for innovative materials. Here we report the successful generation of Bi5, the heaviest analogue of (C5H5). Its use as a ligand in [{IMesCo}2(µ,η55-Bi5)] (1) was realized by reacting (TlBi3)2− with [(IMes)2CoCl] (where IMes is bis(1,3-(2,4,6-trimethylphenyl))imidazol-2-ylidene) in ortho-difluorobenzene. Compound 1 is mixed-valence Co0/CoI as verified by µ-SQUID measurements and density functional theory, and embeds the planar Bi5 cycle in an inverse-sandwich-type manner. Capturing Bi5 represents a landmark in the chemistry of all-metal aromatic molecules and defines a new era for aromatic compounds.