Dimeric and Cyclotrimeric Piano-Stool Vanadium(III) Dihalides with Unusual Differences in V−V Distance and Magnetochemistry. Syntheses, Structures, and Reactivities of (η-C₅Me₄R)₂V₂(μ-Br)₄and the Trivanadium Cluster (η-C₅Me₄R)₃V₃(μ-Cl)₆, New Mid-Valent Organovanadium Synthons

Reductive oligomerization of(C5Me4R)VX3 or addition of(C5Me4R)SnBu3 to VX3L3 (L = thf, tht) yields the (peralkylcyclopentadienyl)vanadium(III) halides (eta(5)-C5Me4R)(2)V-2(mu-Br)(4) and (eta(5)-C5Me4R)(3)V-3(mu-Cl)(6) (R = Me, Et), which can be halogenated to afford (C5Me4R)VX3. Paramagnetic (C5Me4Et)(2)V-2(mu-Br)4 is a four-legged piano-stool dimer in the solid state with a nominal V-V bond (2.565(1) Angstrom), while the spin-frustrated, antiferromagnetic (C5Me4Et)(3)V-3(mu-Cl)(6) is a piano-stool cyclotrimer with two mu-chlorines per nonbonded V ... V edge (3.3732[63] Angstrom).