Effect of L-type ligands on coordination-induced reductive elimination from a titanacyclopentadiene

C-C bond formation via reductive elimination is a fundamental step in organometallic chemistry and catalysis, yet it remains comparatively underexplored for early transition metals. Herein, we present a systematic study of ligand effects on coordination-induced, photochemical C-C reductive elimination of methylenecyclobutene from a well-defined titanacyclopentadiene supported by a bulky pyridinediamido pincer ligand. Screening of various ligands reveals a strong dependence on the coordinating donor, with pyridine and its derivatives providing the highest selectivity, in contrast to phosphines and related ligands, which do not engage with the titanium complex. Notably, pyridine coordination also induces an unusual ligand rearrangement, affording titanium imido complexes featuring a novel dianionic dipyridomethene pincer framework. Protonation of the titanium complexes bearing this ligand cleanly affords the free pro-ligands. Spectroscopic studies support an interaction between pyridine and the titanium complex in the ground state. Additionally, reactivity with isonitriles uncovers an alternative thermal pathway involving insertion into the Ti-C bond. These results highlight the critical role of ligand coordination in controlling photochemical reactivity and C-C bond formation at titanium, providing new insights into LMCT-induced reductive elimination for the formation of strained molecules.