PNNL

Abstract

Two 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 ?3-4mXPNHPRu(PMe3)Cl2. MesPNHP reacts with [(cymene)RuCl2]2 to produce a monomeric species ?3-MesPNHPRuCl2 that reacts with CO forming ?3-MesPNHPRu(CO)Cl2. Dehydrohalogenation of these complexes results in the surprising formation of new Ru-C bonds with one of the ortho methyl groups of the pincer ligands, rather than the expected formation of ?3-RPNPRuLCl complexes. This is the result of transient ?3-RPNPRuLCl formation followed by a 1,2 addition of an ortho C-H bond. In the case of ?4-4mXPNHPRu(PMe3)Cl, the transient amide complex was trapped with CO. However, ?4-MesPNHPRu(CO)Cl does not react with CO or PMe3 to trap the expected amide complex of the reverse C-H addition. Instead, the CO and PMe3 displace the chloride forming cationic complexes. In both cases hemi-lability of the pincer ligand was observed spectroscopically.