The known T-shaped complex ( t Bu3P)Pd(CH3)Cl (1a) and a congener (Ad3P)Pd(CH3)Cl (2) prepared in this work are both bench stable solids under ambient light. They are also indefinitely stable in solution (CDCl3) in the dark. However, we found that irradiation of CDCl3 solution of 1a with blue LED light in the presence of 1,4-cyclohexadiene as an H-atom donor led to the formation of CH4 (33%) and CH3D (43%) over 12 h at RT as determined by 1 H NMR versus cyclohexane as internal standard (Scheme 3). Formation of CH4 still occurred when the reaction was repeated in the absence of 1,4-cyclohexadiene, which indicates the coordinated phosphine and/or the internal standard may also undergo H-atom abstraction. It is proposed that methyl radical is liberated from a photoexcited state of 1a, and the free radical is subsequently quenched by reaction with solvent or an H atom donor present in solution.