Palladium complexes of pincer-structured organosulfur ligands: coordination features, reactivity, and applications

This review provides a focused and critical assessment of organosulfur ligand-supported palladium pincer complexes, with particular emphasis on ligand and framework design, synthetic strategies, coordination chemistry, and structure-reactivity relationships. The underlying principles governing ligand architecture, metal-ligand interactions, and the resulting structural and electronic properties of Pd-S pincer systems are examined to establish their influence on reactivity and function. Particular attention is devoted to their catalytic applications in sustainable organic transformations, including cross-coupling, C-H activation, annulation, C-N and C-B bond formation, organoboron-mediated reactions, allylation, hydrogen-borrowing processes, and small-molecule activation. Their utility in CO 2 valorisation and in the total synthesis of complex natural products, including Crisamicin-A, is also highlighted. Beyond these transformations, Pd-S pincer complexes have demonstrated considerable versatility in polymerisation and other functional-group transformations, such as aldol condensation, tandem double Michael additions, and the synthesis of imidazoline frameworks through condensation of sulfonimines with isocyanoacetates. Particular emphasis is placed on the active and potentially non-innocent role of organosulfur ligands, highlighting their ability to modulate metal-centred reactivity and participate directly in catalytic processes. The review further surveys the structural diversity, biological relevance, and other emerging functional applications of these complexes. Collectively, the analysis establishes the distinctive role of organosulfur ligands in controlling the structure and reactivity of palladium pincer systems and highlights their considerable potential for advancing coordination chemistry and sustainable catalysis.