Abstract: Contemplated subject matter disclosed herein relates generally to organometallic olefin metathesis catalysts, and more particularly to longer-lived olefin metathesis catalysts supported by hemi-labile carbene ligands that bear an arm with one or more donor ligands, as well as the use of such catalysts in metathesis reactions of olefins and olefin compounds. The contemplated subject matter has utility in the fields of catalysis, organic synthesis, polymer chemistry, and industrial and fine chemicals chemistry. This contemplated subject matter serves to reduce the cost of olefin metathesis (OM) processes including in olefin metathesis polymerizations, conversion of vegetable oils into chemicals, and processes in the petrochemical industry. This contemplated subject matter reduces the cost of OM processes by providing OM catalysts that are longer-lived and lead to higher turnover numbers, hence requiring less catalyst to convert a given amount of substrate(s).