Strong Exchange Coupling in a Trimetallic Radical‐Bridged Cobalt(II)‐Hexaazatrinaphthylene Complex

Reducing hexaazatrinaphthylene (HAN) with potassium in the presence of 18‐c‐6 produces [{K(18‐c‐6)}HAN], which contains the S=1/2 radical [HAN](.−). The [HAN](.−) radical can be transferred to the cobalt(II) amide [Co{N(SiMe(3))(2)}(2)], forming [K(18‐c‐6)][(HAN){Co(N′′)(2)}(3)]; magnetic measurements on this compound reveal an S=4 spin system with strong cobalt–ligand antiferromagnetic exchange and J≈−290 cm(−1) (−2 J formalism). In contrast, the Co(II) centres in the unreduced analogue [(HAN){Co(N′′)(2)}(3)] are weakly coupled (J≈−4.4 cm(−1)). The finding that [HAN](.−) can be synthesized as a stable salt and transferred to cobalt introduces potential new routes to magnetic materials based on strongly coupled, triangular HAN building blocks.