Palladacycles as Efficient Precatalysts for Suzuki-Miyaura Cross-Coupling Reactions

Abstract Palladacycles are a paramount class of organometallic compounds which, over recent years, have arisen as valuable devices in the preparation of organometallic substances, especially in cross-coupling processes leading to the formation of carbon-carbon bonds, namely the Suzuki-Miyaura reaction. Palladacycles constitute the precatalysts that provide the necessary palladium itself in an oxidation state dependant on the proposed catalytic cycle, i.e., Pd(0)/Pd(II)//Pd(II)/Pd(IV), or alternatively, where palladium intercedes in the course of the reaction, more often than not palladacycles emerge as intermediates. Well known reasons for their ample use in such performances are, among others, that they are fairly stable and that with few exceptions may be readily prepared in reasonably good yields. After the pioneering work by Herman et al. involving phosphine palladacycles, countless amounts of new palladacycles have been tested for this purpose