A Synthetic Route to a New Surface-Active Phosphine Ligand: 12-DPDP (12-Diphenylphosphinododecylphosphonate)

A water-soluble phosphonate-functionalized phosphine ligand Na2[Ph2P(CH2)12PO3] (8), was prepared in eight steps from cyclododecanone. Phosphine 8 reacts with [Rh(COD)Cl]2 in methanol to give the new complex Na2[Rh(COD)(Ph2P(CH2)12PO3)Cl] (9). Complex 9 is inactive in the catalytic hydrogenation of 1-hexene and cyclohexene due to the decomposition of 9 to rhodium metal in the presence of hydrogen gas. Hydrogenation of decene using [Rh(COD)2]BF4 and 3 equiv. of 8 in an aqueous emulsion was achieved using 1 atm H2. 31P NMR studies on 8 suggest a lack of well-defined aggregation in water, which has been ascribed to the steric bulk of the diphenylphosphino group.