Six and seven membered N-heterocyclic iminato ligands (L) are introduced allowing access a new class of Th(iv) complexes of the type Cp∗2Th(L)(CH3). These complexes were studied in the Tishchenko reaction. Stoichiometric reactions together with kinetic and thermodynamic studies permit us to propose a plausible mechanism. © 2017 The Royal Society of Chemistry.