[5-5]Bitrovacene, (μ-η5:η5-Fulvalenediyl)bis[(η7-cycloheptatrienyl)vanadium]: Synthesis, Structure, and Intermetallic Communication1

Lithiation of trovacene, (η 7 -C 7 H 7 )V(η 5 -C 5 H 5 ), Li/I exchange, and Pd(dppf)Cl 2 -catalyzed homocoupling affords [5-5]bitrovacene 5 2 • . Intermetallic communication manifests itself in typical biradical features of the EPR spectrum and in the resolution of redox splittings of 147 mV for the two subsequent oxidations and 224 mV for the reductions, respectively. 5 2 • adopts a trans conformation in the single crystal (X-ray diffraction) as well as in rigid solution (EPR spectroscopy). A magnetic susceptibility study of 5 2 • reveals weak antiferromagnetic coupling ( J = −2.78 cm - 1 ) of the two V(d 5 ) centers.