This choice is due to inefficiencies in the catalyst reduction and formation of catalytically active Ni(0) species. At the same time, in situ formation of Ni(0)-NHC complexes has disadvantages of instability of Ni(0) precatalysts and NHC ligands, inhibitory effects of cyclooctadiene in some classes of catalytic processes, especially C-H activation processes involving LLHT activation mechanisms, and the precise control of metal-ligand stoichiometry, especially on the small scales required for high throughput experimentation. Ni(0) catalysts that are stabilized by simple alkenes have proven effective across many reaction classes, with more electron-deficient alkenes typically providing more stable but less active catalysts compared with the most commonly employed precursors such as Ni(COD)2. Catalyst 1, initially reported by Cavell, includes IMes as the NHC ligand and dimethyl fumarate as the stabilizing p-acid and serves as a prototypical example of the increased stability and diminished reactivity imparted by the electrondeficient alkene additives. Recent work from our lab built upon this template and examined acrylate, fumarate, and methacrylate p-acids to refine the stability-reactivity balance. While catalyst 1 possesses exceptional stability in air and performs effectively in the oxidation of secondary alcohols, we found that C-C bond-forming processes including aldehyde-alkyne reductive couplings and Buchwald Hartwig aminations were not effective due to deactivation of the catalyst by the fumarate. Systematic variation of the NHC and stabilizing p-acid led to the identification of a number of catalysts that participate effectively with these reaction classes and rapidly initiate without a discernable induction period. Our initial observations found that the optimal p-acid depends on the NHC ligand, and the stability-reactivity continuum can be optimized according to the precise catalytic properties and stability desired. Complexes 2-4 were found to display excellent catalytic properties in aldehyde-alkyne reductive couplings (catalysts 2 and 3) and Buchwald-Hartwig aminations (catalyst 4) and are now sold by commercial vendors (Figure ).