Reductive C(sp 3 )-C(sp 3 ) homo-coupling of benzyl or allyl halides with H 2 using a water-soluble electron storage catalyst.

This paper reports the first example of a reductive C(sp 3 )-C(sp 3 ) homo-coupling of benzyl/allyl halides in aqueous solution by using H 2 as an electron source {turnover numbers (TONs) = 0.5-2.3 for 12 h}. This homo-coupling reaction, promoted by visible light, is catalysed by a water-soluble electron storage catalyst (ESC). The reaction mechanism, and four requirements to make it possible, are also described.