We also found that irradiation of T-shaped complexes in the presence of a less oxidizing radical trap facilitates accumulation of the Pd(I) product during irradiation. The irradiation of 1b in the presence of (Ad3P)Pd(p-C6H4F)Br (7) Methyl radical generation from these monophosphine-ligated T-shaped complexes might be expected to occur with lower photochemical efficiency due to the lack of typical low-lying ligand-based acceptor orbitals (e.g., π*) commonly associated with MLCT in transition metal photochemistry. Quantum yields for Pd(II)-C photocleavage were determined using photo-NMR actinometry (see ESI for full experimental details) according to the method reported by Ji and coworkers. Reactions were performed using either of two in the presence of TEMPO (7 equiv) were consistent with zeroth-order dependence on [Pd] and consequently occurs within a photon-limited kinetic regime inside this concentration range. The quantum yield (Φ) for 1a under these conditions was calculated to be 0.67 (Table , entry 1). Analogous experiments conducted in C6D6 or MeCN-d3 indicated a weak dependence of quantum yield on solvent identity (see ESI, page S86). The related Ad3P-ligated complex 2 gave Φ = 0.36 for formation of TEMPO-CH3 in CDCl3 (Table , entry 3). Importantly, the quantum yields for both T-shaped complexes are higher compared to the reference complex 3 (Φ = 0.11) under otherwise identical conditions (Table , entry 5). Note that repetition of these measurements in the absence of TEMPO, which absorbs light in the visible region and might interfere with quantum yield measurements, apparently gave only a modest increase for T-shaped 1a (Φ = 0.67-0.73) or αdiimine complex 3 (Φ = 0.11-0.16) as shown in Table , entries 1 vs 2 or 4 vs 5. We conducted several additional experiments and computations to understand the origin of the counterintuitive trend of greater quantum efficiency for the Tshaped complexes compared to the diimine-ligated complex. Conditions: a solution of Pd complex (60 mM for 1a; 30 mM for 3) and TEMPO (7 equiv.) in CDCl3 were irradiated at room temperature using photo-NMR (440 nm LED). The initial rate was taken from each reaction and used to calculate Φ. See ESI, page S111 for full details.