Synthesis, crystal structures, and redox behavior of some pentamethylcyclopentadienyl arene ruthenium salts

Hexafluorophosphates of (eta(5)-pentamethylcyclopentadienyl)(eta(6)-arene) ruthenium cations (arene 1,3,5-triethylbenzene, 1,3,5-tris(trimethylsilylmethyl) benzene, and pentamethylbenzene) have been obtained from the reaction of [Ru(eta(5) C5Me5)NCCH3)(3)]+PF6- with the appropriate arene; their X-ray single-crystal structures have been determined and compared to those of related compounds. The electrochemistry of these cations is compared to that of other [Ru(eta(5)-C5Me5)(eta(6)-arene)](+) and [Fe(eta(C5Me5)-C-5)( eta(6)-arene)](+) species; the 1,3,5-C6H3(CH2SiMe3)(3) derivative is reduced at the most cathodic potential (E-pc = -2.96 V vs. ferrocenium/ferrocene). Reduction with sodium amalgam gives a dimer, [Ru(eta(5)-C5Me5)](2)[mu-eta(5): eta(5)-(arene)(2)], in the case of arene 1,3,5-C6H3Et3, analogous to what has been previously reported for the mesitylene complex, and a mixture of products when arene C6HMe5. The 1,3,5-C6H3( CH2SiMe3)(3) derivative is comparatively unreactive to sodium amalgam, although long reaction times lead to desilylation and formation of [Ru(eta(5)-C5Me5)](2)[mu-eta(5): eta(5)-C6H3Me3C6H3Me3]. Use of sodium -potassium alloy, on the other hand, leads to formation of a 18-electron anionic Ru-0 complex: K+[Ru(eta(5)-C5Me5){ eta(4)-1,3,5-C6H3(CH2SiMe3)(3)}](-). (C) 2013 Elsevier B. V. All rights reserved.