Organometallic Supramolecular Mixed-Valence Cobalt(I)/Cobalt(II) Aquo Complexes Stabilized with the Water-Soluble Phosphine Ligand p-TPPTP (p-triphenylphosphine triphosphonic acid)

Reaction of the water-soluble phosphine phosphonic acid p-TPPTP(H)6 (p-triphenylphosphine triphosphonic acid) with Co2(CO)8 under biphasic conditions results in the formation of Co6(CO)3(p-TPPTP)2(H2O)24·24H2O (2) or Co4(CO)3(p-TPPTP)2(H2O)24·24H2O (3) depending on the pH of the solution. These supramolecular organometallic Co(I)/Co(II) complexes contain either six (2) or four (3) crystallographically distinct cobalt ions. The cation [Co(CO)3(p-TPPTP)2]+ from 2 was reacted with titanium tetraisopropoxide via a sol−gel method to give a titania-supported Co(I) olefin hydroformylation catalyst, which was characterized using solid-state 31P NMR, IR, and XPS.