This Perspective discusses the application of transition metal-catalyzed reactions to the formation of rings, oligomeric chains and macromolecules based on p-block and d-block elements. For example, the catalytic dehydrocoupling of Group 13–Group 15 Lewis acid–Lewis base adducts (e.g. 1° or 2° phosphine–boranes or amine–boranes) has been shown to yield high molecular weight polyphosphinoboranes, cyclic aminoborane species or borazines. The metal-catalyzed ring-opening polymerization (ROP) of silicon-bridged [1]ferrocenophanes allows molecular weight control through the use of silane capping agents, and permits the synthesis of block copolymers via the use of reactive polymer end-groups.