N₂ Provides Insight into the Mechanism of H−C(sp³) Bond Cleavage

Exchange of deuterium in d6-benzene with all C−H sites in (PNP)Ru(OTf), where PNP is N(SiMe2CH2PtBu2)2 and OTf is OSO2CF3, is rapid at 22 °C. Although intact planar triplet (PNP)Ru(OTf) binds N2 only very weakly, these reagents are observed to react rapidly to give a diamagnetic 1:1 adduct whose structure has one tBu C−H bond cleaved: the carbon binds to Ru but the hydrogen is on the PNP nitrogen, creating a secondary amine ligand bound to RuII. It is suggested that the benzene C−D cleavage and the N2 product of tBu C−H bond heterolysis both derive from a common intermediate, [HN(SiMe2CH2PtBu2)(SiMe2CH2PtBuCMe2CH2)] Ru(OTf); the formation energy and structure of this species are discussed on the basis of DFT results.