CC coupling reactions are ubiquitous in synthetic chemistry, joining together fragments of larger molecules within overall synthetic schemes. Many obvious operational advantages would result from catalyzing such processes heterogeneously, however, there has been much controversy over whether metal nanoparticles (typically Pd) can be used in this role, or if catalysis in such cases occurs instead on metal ions leached into solution. In this mini-review selected examples of attempts to distinguish the homo- or hetero-geneity of such reactions, using Pd and Au nanoparticles, are highlighted. In particular, several interesting recent results are explored that demonstrate such metal nanoparticle catalyzed reactions can occur in a heterogeneous mode. Copyright (c) 2012 Society of Chemical Industry