Structure, Magnetism, and Multi-electron Reduction Reactivity of the Inverse Sandwich Reduced Arene La²⁺ Complex [{[C₅H₃(SiMe₃)₂]₂La}₂(μ‑η⁶:η⁶‑C₆H₆)]^1–

The magnetic properties and multi-electron reductive reactivity of the bimetallic inverse sandwich La2+ complex salt, [K­(18-crown-6)­(THF)2]­[(Cp″2La)2­(μ-η6:η6-C6H6)]·THF, 1 (Cp′′ = C5H3­(SiMe3)2), originally described by Lappert et al., have been examined. The compound was prepared by reduction of Cp″3La with potassium metal in benzene and crystallographically characterized. Compound 1 can be described as containing two 5d1 La­(II) ions bridged by a planar (C6H6)1– benzenide bridged radical monoanion, with fits to its variable-temperature magnetic susceptibility data revealing strong antiferromagnetic exchange coupling, with JLa–C6H6 > |−400 cm–1|. The multi-electron reduction reactivity of 1 was explored in reactions with anthracene, naphthalene, and cyclooctatetraene. Compound 1 reduces anthracene to give Cp″2La­(μ-η6:​η6-C14H10)­K­(18-crown-6), 2, which contains a nonplanar anthracenide dianion with an end ring interacting with La­(III) and the central ring interacting with potassium. The reaction of 1 with naphthalene forms [K­(18-crown-6)­(THF)2]­[Cp″2La­(η4-C10H8)], 3, which has a naphthalenide dianion with one planar ring and one ring bent such that four carbons atoms have 2.663(4)–2.743(4) Å La–C distances. 1,3,5,7-Cyclooctatetraene is reduced by 1 to give the bridged cyclooctatetraenyl complex salt [K­(18-crown-6)]­[(μ-η8:η2-C8H8)­LaCp″­(μ-η8:η8-C8H8)­LaCp″2], 4