Cross-coupling partner

In cross-coupling reactions, the component reagents are called cross-coupling partners or simply coupling partners. These reagents can be further classified according to their nucleophilic vs electrophilic character:
 * R-X +  R'-Y  →   R-R'  +  XY

Typically the electrophilic coupling partner (R-X) is an aryl halide, but triflates are also used. Nucleophilic coupling (R'-Y) partners are more diverse. In the Suzuki reaction, boronic esters and boronic acids serve as nucleophilic coupling partners. Expanding the scope of coupling partners is a focus methods development in organic synthesis.