A new thorium monoalkyl complex, Th(CH2SiMe3)(L-3) (L = MeC((NPr)-P-i)(2)) (2), undergoes insertion of chalcogen atoms resulting in a series of thorium chalcogenolate complexes, Th(ECH2SiMe3)(L-3) (E = S, SS, Se, Te; 5-8). Complex 6 represents the first alkyl disulfide thorium species and illustrates the ability of 2 to undergo controllable, stoichiometric atom insertion. All complexes have been characterized by H-1 and C-13 NMR spectroscopy, FTIR, EA, and melting point, and in the case of 1, 2, and 4-8, X-ray crystallography. Insertion was achieved by balancing the thermodynamic driving force of chalcogenolate formation versus the BDE of the pnictogen-chalcogen bond in the transfer reagent. Utilizing Me3NO as an oxygen atom transfer reagent led to C-H activation and SiMe4 extrusion rather than oxygen atom insertion, resulting in the alkoxide complex Th(OCH2NMe2)(L-3) (4).