The use of ball mills enabled the efficient mechanosynthesis of a variety of N-aryl,N-alkyl imidazolium salts and of corresponding NHC silver(I) complexes. Transmetalation with ruthenium via mechanochemistry allowed the rapid access (from 1.5 min to 1 h) to complexes having a similar structure to Noels-type precatalysts. Evaluation of the complexes in the ring-opening metathesis polymerization of norbornene in different solvent, including nontoxic ones, showed a high catalytic activity for one of them, comparable to that of the Noels catalyst.