The equilibrium between aluminum alkoxides and 1-(diphenylphosphinoyl)-2-(diphenylphosphino)ethane

The reaction of Ph2P(O)CH2CH2PPh2 with several aluminum alkoxides was studied. No reaction was detected with [Al(OEt)3]n or [Al(OPri)3]4. In contrast, [Al(OBut)3]2 or [Al(OBus)3]n in methylene chloride are in equilibrium with (RO)3AlOPPh2CH2CH2PPh2. In the case of [Al(OBus)3]n equilibrium constants have been obtained and are consistent with: 1/2[Al(OBus)3]2+Ph2P(O)CH2CH2PPh2⇌(BusO)3AlOPPh2CH2CH2PPh2. Plots of −RT ln Keq versus 1/T between −20 and 35 °C yield ΔH=10.5±0.5 kJ mol−1 and ΔS=38±2 J K−1 mol−1.