Formation of Phosphino-Substituted Isocyanate by Reaction of CO2 with Group 2 Complexes Based on the (Me3Si)(i-Pr2P)NH Ligand

The group 2 complexes [(Me3Si)(i-Pr2P)-N](2)M(THF)(x) (M = Mg, x = 1; M = Ca/Sr, x = 2) as well as an unusual dimagnesium complex {[(Me3Si)(i-Pr2P)-N](3)Mg}Mg(n-C4H9) have been prepared and characterized by multinuclear NMR spectroscopy and single crystal X-ray diffraction. Each complex was shown to react with CO2 under extremely mild conditions (15 min, 1 atm, room temperature) to give the isocyanate (i-Pr)(2)P-N=C=O. The independent syntheses of (i-Pr)(2)P N=C=O and the carbodiimide dimer [(i-Pr)(2)PNCNP(i-Pr)(2)](2) are also reported.