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

The selective alkylation (Me or <i>tert</i>-butyl) of a doubly linked dicyclopentadiene ligand is presented. The reaction of (C₅H₃(<i>t</i>-Bu))₂(CMe₂)₂ (<b>4a</b>,<b>b</b>), the di-<i>tert</i>-butyl-substituted ligand, with RuCl₃·3H₂O in MeOH at 140 °C for 15 min, followed by heating in CHCl₃, gave the chloro-bridged complex <i>cis</i>-{(η⁵-C₅H₂(<i>t</i>-Bu))₂(CMe₂)₂}­Ru₂(μ-Cl)₂Cl₂ (<b>5</b>) in 28% yield. Reduction of <b>5</b> with Zn in MeCN gave the chloro-bridged tetrakis­(acetonitrile) complex <i>cis</i>-[{(η⁵-C₅H₂(<i>t</i>-Bu))₂(CMe₂)₂}­Ru₂(MeCN)₄(μ-Cl)]⁺ (<b>6</b>) in 62% yield. Addition of AgOTf to <b>6</b> in MeCN removed the bridging chloro ligand and gave [<i>cis</i>-{(η⁵-C₅H₂(<i>t</i>-Bu))₂(CMe₂)₂}­Ru₂(MeCN)₆]­[OTf]₂ (<b>7</b>) in 38% yield. The X-ray crystal structures of <b>5</b> and <b>6</b> are reported