Formation of a Bridging Phosphinidene Thorium Complex

The synthesis and structural determination of the first thorium phosphinidene complex are reported. The reaction of 2 equiv of (C5Me5)(2)Th(CH3)(2) with H2P(2,4,6-(Pr3C6H2)-Pr-i) at 95 C produces [(C5Me5)(2)Th](2)(mu(2)-P[(2,6-CH2CHCH3)2-4-(PrC6H2)-Pr-i] as well as 4 equiv of methane, 2 equiv from deprotonation of the phosphine and 2 equiv from C-H bond activation of one methyl group of each of the isopropyl groups at the 2- and 6-positions. Transition state calculations indicate that the steps in the mechanism are P-H, C-H, C-H, and then PH bond activation to form the phosphinidene.