The ubiquity of N-heterocyclic carbenes (NHCs) in diverse areas of chemical research typically arises from their potent stabilising capabilities and role as innocent spectators to stabilise otherwise non-bottleable compounds and complexes. This has, until now, been particularly true for NHC-stabilised stannylenes, with no exceptions reported thus far. Herein, we demonstrate that the combination of heteroleptic terphenyl-/amido-based stannylenes and tetra-alkyl substituted NHCs renders the corresponding NHC-ligated stannylenes highly reactive, yet isolable. In solution, this induces sterically controlled inter- and intramolecular C(sp3)-H bond scissions, resulting in the selective formation of stannylene metallocycles that depend on both the NHC source and the meta-terphenyl ligand coordinated to tin.