Visible-Light-Induced Olefin Activation Using 3D Aromatic Boron-Rich Cluster Photooxidants

We report a discovery that perfunction-alized icosahedral dodecaborate dusters of the, type B-12(OCH2Ar)(12) (Ar = Ph or C6F5) can undergo photoexcitation with visible light, leading to a new class of metal free photooxidants. Excitation in these species occurs as a result of the charge transfer between low-lying orbitals located on the-benzyl substituents and an unoccupied orbital delocalized throughout the boron cluster core. Here we show how these species, photo-excited with a benchtop blue LED source, can exhibit excited-state reduction potentials as high as 3 V,and can participate in electron transfer processes with a broad range of styrene monomers, initiating their polymerization. Initiation is observed in cases of both electron-rich and electron deficient styrene monomers at cluster loadings as low as 0.005 mol%. Furthermore, photo-excitation of B-12(OCH2-C6F5)(12) in the presence of a less activated olefin such as isobutylene result's in the production of highly branched poly(isobutylene). This work introduces a new class of air stable, metal-free photo-redox: reagents capable of mediating chemical transformations.