Efficient ruthenium metathesis catalysts containing carborane ligands

A first generation Hoveyda–Grubbs ruthenium complex with a closo-1,2-C2B10H11 tag has been prepared. This new catalyst was tested in ring-closing metathesis (RCM) reactions and proved to be quite efficient. In addition, the recovery and reuse of a previously reported second generation Hoveyda–Grubbs ruthenium carbene complex bearing an ionic [nido-7,8-C2B9H10]− tag was further studied. When used in an ionic liquid, the catalyst can be conveniently recycled and reused with only a very slight loss of activity for the RCM of oxygen-containing and N-protected substrates with di- or trisubstituted double bonds.