A Bisphosphine Usable for Metal-free Hydrogenations

1,8-Bis(diphenylphosphino)naphthalene (1) has two diphenylphosphino groups and acts as a bulky Lewis base. The bulkiness of 1 is also effective for forming unquenched Lewis acid-base pairs, “frustrated Lewis pairs (FLPs)”, by treatment with a Lewis acid like tris(pentafluorophenyl)borane (2). Erker et al. have applied them to activate a molecular hydrogen and the subsequent metal-free hydrogenations of silyl enol ethers. In this reaction, molecular hydrogens seem to be activated by the FLP-induced acid-base cooperation.