Tetrakis([5]trovacenyl)tin: Synthesis, structure, and intramolecular communication

In order to study intermetallic interactions in a tetranuclear complex with tetrahedral disposition of paramagnetic central metal atoms, the organometallic tetraradical [(eta(7)-C7H7)V(eta(5)-C5H4)](4)Sn (3(4 center dot)), tetra([5]trovacenyl)tin, was prepared, characterized by X-ray diffraction, and subjected to EPR spectroscopy, magnetic susceptometry, and cyclic voltammetry. The binuclear complex [(eta(7)-C7H7)V(eta(5)-C5H4)](2)Ph2Sn (4(2 center dot)) was also obtained to serve as a reference molecule. The EPR hyperfine pattern attests to exchange coupling which approaches the fast exchange limit, i.e., J(EPR) (3(4 center dot)) > a(V-51) = 0.0067 cm(-1). For the dinuclear complex simulation afforded the value parallel to J(4(2 center dot))parallel to = 1.4 cm(-1); magnetic susceptometry yielded the exchange coupling constant J(chi)(4(2 center dot)) = -1.78 cm(-1). No quantitative data could be derived for the tetranuclear complex; however, the gradation J(3(4 center dot)) < J(4(2 center dot)) applies. This may be a result of competing interactions of opposite sign or of spin frustration, as has been discussed previously for tetrahedral spin clusters of the Werner type. Redox splittings for tetrakis([5]trovacenyl)tin are smaller than those for tetrakis(ferrocenyl)silicon.