The activation of C-H bonds by transition metal complexes can proceed by multiple pathways, including the 1,2-addition of C-H bonds across early transition metal imido bonds. [1][2][3][4] Such transformations are potentially useful since subsequent N-C reductive elimination (RE) would produce a free amine; however, RE is often a high-energy reaction for early transition metals. In contrast, REs of N-C and O-C bonds form the foundation of routes to aryl amines and ethers using late transition metal catalysts. 5,6 Thus, it is anticipated that accessing the net addition of C-H bonds (regardless of the specific mechanism) across late transition metal M-X bonds (X ) anionic N or O-based ligand) could ultimately lead to the development of routes for hydrocarbon functionalization. Late transition metal oxo and related systems are known to initiate hydrogen atom abstraction; 7 however, these transformations do not involve direct interaction of the metal center with the external C-H substrate. In addition, Ru-amido complexes have been demonstrated to deprotonate "acidic" C-H bonds. 8 The previously reported complex TpRu(PMe 3 ) 2 (OTf) (OTf ) trifluoromethanesulfonate) reacts with CsOH‚H 2 O in refluxing toluene to produce TpRu(PMe 3 ) 2 (OH) (1). A solid-state X-ray diffraction study of 1 has confirmed its structure as a monomeric Ru ( Kinetic studies reveal that H/D exchange at the hydroxide ligand of 1 in C 6 D 6 is first-order with k obs ) 8.0(2) × 10 -5 s -1 (80°C, t 1/2 ≈ 2.4 h). This rate of H/D exchange suggests a more active catalyst for H/D scrambling between H 2 O and C 6 D 6 than has been observed; however, the poor solubility of H 2 O in benzene likely slows the rate of catalysis. The addition of 10 mol % of TpRu(PMe 3 ) 2 (OTf) (precursor to 1) to a solution of 1 and C 6 D 6 does not increase the rate of H/D exchange at the hydroxide ligand of 1. The presence of coordinating ligands suppresses the rate of H/D exchange at the hydroxide ligand as well as the rate of catalysis, which is consistent with a metal-mediated process. For example, heating a solution of complex 1 in C 6 D 6 in the presence of 0.1 equiv (based on 1) of PMe 3 results in no observable H/D exchange at the hydroxide ligand after 168 h at 80°C. The addition of the "non-coordinating" base 2,6-lutidine does not increase the rate of H/D exchange at the hydroxide ligand.In order for the proposed pathway to be viable, complex 1 must access a five-coordinate species on a time scale that is consistent with the observed H/D exchange at the hydroxide ligand. Monitoring the rate of exchange of PMe 3 upon combination of complex 1 with PMe 3 -d 9 at 80°C reveals that k obs ) 1.7(1) × 10 -4 s -1 (t 1/2 ≈ 68 min). Thus, the rate of PMe 3 exchange is greater than the rate of H/D exchange and indicates that external substrates (e.g., C 6 D 6 ) † North Carolina State University. ‡ University of North Texas. § West Virginia University.

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