Reactions of Cp*₂Yb(THF)₂ with TCNQ and TCNB. A Novel Type of Reactivity of TCNQ toward Metallocenes. The First Example of the π-Dimer [TCNB₂]²⁻

The reaction of Cp*2Yb(THF)2 with an equimolar amount of 7,7,8,8-tetracyanoquinodimethane (TCNQ) affords the Yb(III) complex [Cp*2Yb(CH3CN){(μ-CN)2C(C6H4)C(CN)2(C5Me5)}]2, containing a monoanionic polycyano ligand arising from one-electron reduction of TCNQ and the coupling of its methylidene carbon with the allylic carbon atom of a Cp* fragment. Reaction of Cp*2Yb(THF)2 with 1,2,4,5-tetracyanobenzene (TCNB) in a 1:1 molar ratio results in oxidation of the ytterbium atom and the formation of the Yb(III) complex [Cp*2Yb{(μ-CN)2(C6H4)(CN)2}]2the first example of the dianionic π-dimer [TCNB2]2− participating in μ:η4 bonding with two metal centers.