A copper(I)-mediated reductive dechlorination reaction involving an "internal" chloromethylene substrate at the pyridyl 6-position of one TMPA arm (TMPA TPA tris (2-pyridylmethyl)amine) leads to a 1:1 ratio of the starting ligand 6ClCH(2)-TMPA and a new methyl-TMPA product, 6CH(2)H -TMPA. On the basis of observed product distributions and a kinetic study, a reaction mechanism involving intramolecular oxidative insertion of Cu(I) to the C-Cl substrate is suggested. The resulting organometallic intermediate is then protonated, leading to the observed products.