During optimization of the ratio of BiCl 3 to TBACl ligand, an interesting reactivity pattern was observed (Figure ). In situ formed BiCl 4 -and BiCl 5 2-are competent catalysts when irradiated at 385 nm giving comparable yields of 2c, whereas at 400 nm only BiCl 5 2-is active. We followed the observation by performing UVvis titration studies. The sequential addition of one equivalent TBACl to BiCl 3 resulted in a bathochromic shift, which increased upon adding a second equivalent, and the third chloride addition led to less significant changes of absorption properties. This suggests that BiCl 5 2-is indeed the preferred coordination mode of bismuth chlorides. Consistent with this finding are Gibbs free energy calculations performed by the Hunt group. These show that Bi 3+ ions favour a square pyramidal coordination in excess of chloride over other structures. The synthetic scope of this photocatalytic bismuth mediated Giese-type coupling was explored to showcase its generality (Scheme 1). Differently substituted electron-deficient alkenes bearing nitrile, carboxyl and sulfone groups were viable coupling partners (2-8b). Nitrile group containing radical traps gave best product yields. Less steric hindrance around the radical trap seemed to be beneficial, hinting at close interactions of reaction intermediates and bismuth catalyst. The free carboxylic acid functional group of 6c and 7c are tolerated under the pH neutral conditions of this coupling. This shows that coordination of carboxylic acid to bismuth without base is unlikely to happen. The protocol was successfully upscaled to gram scale (8c) without any significant loss of efficiency at higher irradiation wavelength of 400 nm (Scheme S4). The chlorine radical-mediated HAT allows the C-H bond activation of a broad range of starting materials. The selectivity of abstraction is steered to the most hydric hydrogen atoms -an established abstraction pattern of the electrophilic chlorine radical. Compounds 12c and 18c illustrate the described selectivity. The benzylic -CH 3 group of 4-methylanisol ( ) is functionalized in the presence of -OCH 3 moiety which remains intact. In the case of more functionalized anisole derivative 18a, the electron-withdrawing ester group deactivates the benzylic position enough that HAT is happening exclusively at the previously untouched aromatic -OCH 3 group. Similarly, the αketo-CH 3 group of benzodioxol 17a is deactivated enough, that functionalisation occurs only at the dioxol motive. In general, α-to heteroatom C-H bond containing precursors are high-yielding.