Intramolecular 1,2 C‐H Addition of o‐Methyl Groups to Form Unique Ruthenium Pincer Tuck‐in Complexes

New RPNHP ligands containing 2,4-xylyl (4mXPNHP) and mesityl (MesPNHP) groups on the phosphorus atoms were synthesized. 4mXPNHP reacts with [(cymene)RuCl2]2 followed by PMe3 to produce κ3-4mXPNHPRu(PMe3)Cl2. MesPNHP reacts with [(cymene)RuCl2]2 to produce monomeric κ3-MesPNHPRuCl2 that reacts with CO forming κ3-MesPNHPRu(CO)Cl2. Surprisingly, dehydrohalogenation of these complexes results in the activation of ortho methyl groups of the pincer ligands, rather than formation of κ3-RPNPRuLCl complexes. This results from transient κ3-RPNPRuLCl formation followed by 1,2-addition of an ortho C-H bond across the Ru-amide bond. The transient amide complex of κ4-4mXPNHPRu(PMe3)Cl was trapped with CO forming κ3-4mXPNPRu(PMe3)(CO)Cl. In contrast, κ4-MesPNHPRu(CO)Cl does not react with ligands to trap the expected amide complex of reverse C-H addition. Instead, CO and PMe3 displace the chloride ligand forming cationic complexes. In both cases, hemi-lability of the pincer ligand was observed spectroscopically. The new complexes serve as precursors to moderately active catalysts for the acceptorless dehydrogenative coupling of n-butanol.