Functionalization of Carbon Monoxide and tert-Butyl Nitrile by Intramolecular Proton Transfer in a Bis(Phosphido) Thorium Complex.

We report intramolecular proton transfer reactions to functionalize carbon monoxide and tert-butyl nitrile from a bis(phosphido) thorium complex. The reaction of (C5 Me5 )2 Th[PH(Mes)]2 , Mes=2,4,6-Me3 C6 H2 , with 1 atm of CO yields (C5 Me5 )2 Th(κ2 -(O,O)-OCH2 PMes-C(O)PMes), in which one CO molecule is inserted into each thorium-phosphorus bond. Concomitant transfer of two protons, formerly coordinated to phosphorus, are now bound to one of the carbon atoms from one of the inserted CO molecules. DFT calculations were employed to determine the lowest energy pathway. With tert-butyl nitrile, t BuCN, only one nitrile inserts into a thorium-phosphorus bond, but the proton is transferred to nitrogen with one phosphido remaining unperturbed affording (C5 Me5 )2 Th[PH(Mes)][κ2 -(P,N)-N(H)C(CMe3 )P(Mes)]. Surprisingly, reaction of this compound with KN(SiMe3 )2 removes the proton bound to nitrogen, not phosphorus.