Heteroleptic copper(I) complexes [Cu(dmp)(N^P)]BF 4 for photoinduced atom-transfer radical addition reactions.

Earth-abundant copper(I) coordination complexes of an imine-phosphine and a diimine have been developed as visible-light photocatalysts. Reaction of [Cu(MeCN) 4 ]BF 4 with hetero-bidentate phosphinopyrazole (phpz) ligand R 1 R 2 C 3 HN 2 PPh 3 (R 1 = R 2 = H (1a); R 1 = H, R 2 = Me (1b); R 1 = H, R 2 = Ph (1c); R 1 = R 2 = Me (1d)) and 2,9-dimethyl-1,10-phenanthroline (dmp) gave four heteroleptic bis-chelate Cu(I) complexes [Cu(dmp)(R 1 R 2 C 3 HN 2 PPh 3 )]BF 4 (R 1 = R 2 = H (2a); R 1 = H, R 2 = Me (2b); R 1 = H, R 2 = Ph (2c); R 1 = R 2 = Me (2d)) with distorted tetrahedral geometries. Complexes 2a-2d exhibited broad absorption in the visible spectrum and could facilitate photochemical intermolecular atom-transfer radical addition reactions of CBr 4 , or CCl 3 Br, CHI 3 to styrenes in yields up to 91% and with a broad substrate scope. The absorption, emission, redox potential and photocatalytic activity were dependent on the substituents on the phpz ligand. Mechanistic studies supported an atom-transfer radical addition (ATRA) mechanism.