ELECTROCHEMISTRY OF OCTAMETHYL[3]RUTHENOCENOPHANE - SYNTHESIS AND STRUCTURE OF THE FIRST DICATIONIC DERIVATIVE OF RUTHENOCENE, TA(5)-C(5)ME(4)(CH2)(3)C(5)ME(4))RU(NCME)](PF6)(2)

The octamethyl[3]ruthenocenophane {eta(5):eta(5)-C(5)Me(4)(CH2)(3)C(5) Me(4)}RU (1) was synthesized by the reaction of RuCl3 . 3H(2)O with HC (5)Me(4)(CH2)(3)C(5)Me(4)H in triethylene glycol at 200 degrees C. Oth er sterically congested ruthenocene derivatives, (eta(5)-C(5)Me(5))(2) Ru (2) and (eta(5)-C(5)Me(4)H)(2)RU (3), were also prepared in high yi elds by this simple method. The cyclic voltammogram of 1 in CH2-Cl-2 s hows a reversible le oxidation wave at E(1/2) = +0.36 V vs SCE, while that in CH3CN exhibits a 2e oxidation wave at +0.30 V vs SCE and a sma ller 2e reduction wave at -0.04 V vs SCE. The bulk electrolysis of 1 a t +0.30 V vs SCE in 0.1 M NH4PF6/CH3CN gave the dication salt containi ng CH3CN as an additional ligand, a(5)-C(5)Me(4)(CH2)(3)C(5)Me(4)}RU-( NCMe)](PF6)(2) (4), almost quantitatively. The ECE mechanism including the CH3CN coordination/dissociation process was suggested for the red ox reaction between 1 and its dication [1 . NCCH3](2+) based on the cy clic voltammograms of 1-4 as well as the crystal structure analysis of 1 and 4. Crystal data for 1: C21H30Ru, space group P2(1)/a, a = 15.27 2(2) Angstrom, b = 11.090(1) Angstrom, c = 10.991(2) Angstrom, beta = 101.07(2)degrees, V = 1826.8(4) Angstrom(3), Z = 4, R = 0.052, and R(w ) = 0.084 based on 4435 reflections with [\F-0\ > 3 sigma(F-0)]. Cryst al data for 4: C23H33F12-NP2Ru, space group Pmnm, a = 11.031(1) Angstr om, b = 14.883(1) Angstrom, c = 8.973(1) Angstrom, V = 1473.1(2)Angstr om(3), Z = 2, R = 0.059, and R(w) = 0.085 based on 2528 reflections wi th [\F-0\ > 3 sigma(F-0)].