19-ELECTRON ARENECYCLOPENTADIENYL COMPLEXES OF RUTHENIUM

A series of arenecyclopentadienyl complexes, i.e., [Ru(eta(5)-C(5)R(5) )(eta(6)-arene)](+) (1, R = H, arene = C6H6; 2, R = Me, arene = C6H6; 3, R = H, arene = C(6)H(3)Me(3); 4, R = Me, arene = C(6)H(3)Me(3); 5, R = H, arene = C(6)Me(6); 6, R = Me, arene = C(6)Me(6)) was studied by cyclic voltammetry. These compounds are capable of both oxidation and reduction. The reduction potential values depend on the number of met hyl groups in the complex. Reduction of benzene complexes 1 and 2 by s odium amalgam in THF leads to the formation of decomplexation products , the addition of hydrogen to benzene, and dimerization of the benzene ligands. Both chemical and electrochemical reductions of mesitylene c omplexes 3 and 4 result in dimeric products [(eta(5)-C(5)R(5))Ru(mu-et a 5:eta 5-Me(3)H(3)C(6)C(6)H(3)Me(3))Ru(eta(5)-C(5)R(5))] (14, R = H; 15, R = Me). The action of sodium amalgam on compound 5 gives products of hydrogen addition to both hexamethylbenzene (17) and cyclopentadie nyl (18) ligands along with the major product, the dimer -eta(5):eta(5 )-Me(6)C(6)C(6)Me(6))Ru(eta(5)-C5H5)] (16). In contrast to 5, its perm ethylated analog 6 is only capable of adding hydrogen to the hexamethy lbenzene ligand.