Selective Dialkylation of a Doubly Linked Dicyclopentadiene Ligand and the Ensuing Ruthenium Complexes

The selective alkylation (Me or tert-butyl) of a doubly linked dicyclopentadiene ligand is presented. The reaction of (C5H3(t-Bu))(2)(CMe2)(2) (4a,b), the di-tert-butyl-substituted ligand, with RuCl3 center dot 3H(2)O in MeOH at 140 degrees C for 15 min, followed by heating in CHCl3, gave the chloro-bridged complex cis-{(eta(5)-C5H2(t-Bu))(2)(CMe2)(2)}Ru-2(mu-Cl)(2)Cl-2 (5) in 28% yield. Reduction of 5 with Zn in MeCN gave the chloro-bridged tetrakis(acetonitrile) complex cis-[{(eta(5)-C5H2(t-Bu))(2)(CMe2)(2)}Ru-2(MeCN)(4)(mu-Cl)](+) (6) in 62% yield. Addition of AgOTf to 6 in MeCN removed the bridging chloro ligand and gave [cis-{(eta(5)-C5H2(t-Bu))(2)(CMe2)(2))Ru-2(MeCN)(6)[OTf](2) (7) in 38% yield. The X-ray crystal structures of 5 and 6 are reported.