text: A variety of experimental concerns exist for IMHR reactions. Although most of the common Pd(0) catalysts are commercially available (Pd(PPh), Pd(dba), and derivatives), they may also be prepared by simple, high-yielding procedures. Palladium(II) acetate is cheap and may be reduced in situ to palladium(0) with phosphine. Three equivalents of phosphine per equivalent of palladium acetate are commonly used; these conditions generate Pd(PR) as the active catalyst. Bidentate phosphine ligands are common in asymmetric reactions to enhance stereoselectivity.
  A wide variety of bases may be used, and the base is often employed in excess. Potassium carbonate is the most common base employed, and inorganic bases are generally used more often than organic bases. A number of additives have also been identified for the Heck reaction—silver salts may be used to drive the reaction down the cationic pathway, and halide salts may be used to convert aryl triflates via the neutral pathway. Alcohols have been shown to enhance catalyst stability in some cases, and acetate salts are beneficial in reactions following the anionic pathway.