N<sub>2</sub> Provides Insight into the Mechanism of H−C(sp<sup>3</sup>) Bond Cleavage

Exchange of deuterium in <i>d</i><sub>6</sub>-benzene with all C−H sites in (PNP)Ru(OTf), where PNP is N(SiMe<sub>2</sub>CH<sub>2</sub>P<sup>t</sup>Bu<sub>2</sub>)<sub>2</sub> and OTf is OSO<sub>2</sub>CF<sub>3</sub>, is rapid at 22 °C. Although intact planar triplet (PNP)Ru(OTf) binds N<sub>2</sub> only very weakly, these reagents are observed to react rapidly to give a diamagnetic 1:1 adduct whose structure has one <sup>t</sup>Bu C−H bond cleaved:  the carbon binds to Ru but the hydrogen is on the PNP nitrogen, creating a secondary amine ligand bound to Ru<sup>II</sup>. It is suggested that the benzene C−D cleavage and the N<sub>2</sub> product of <sup>t</sup>Bu C−H bond heterolysis both derive from a common intermediate, [HN(SiMe<sub>2</sub>CH<sub>2</sub>P<sup>t</sup>Bu<sub>2</sub>)(SiMe<sub>2</sub>CH<sub>2</sub>P<sup>t</sup>BuCMe<sub>2</sub>CH<sub>2</sub>)] Ru(OTf); the formation energy and structure of this species are discussed on the basis of DFT results.