C–H Bond Activation by a Ruthenium(II) β‐Diketonate Complex: A Mechanistic Study.

Ruthenium(II)‐catalysed C–H bond activation of arenes containing a functional directing group depends on the ligand coordinated to ruthenium(II). In this study, 2‐phenylpyridine C–H activation catalysed by a "piano‐stool" ruthenium(II) complex containing a fluorinated β‐diketonate ligand was examined by ESI‐MS in combination with CID experiments. [Ru(β‐diketonate)(CTPhPy)Cl]+ was identified as an active intermediate, and its collisional activation leads to C–H activation. CID analysis indicates proton transfer from the phenylpyridine to the chlorine anion, showing HCl elimination, while the β‐diketonate ligand is retained in the complex together with the activated phenylpyridine. Furthermore, DFT calculations were performed for the neutral analogue [Ru(β‐diketonate)(PhPy)Cl] to identify all ruthenium intermediates along the C–H activation reaction pathway. The results suggest that the most stable structure of [Ru(β‐diketonate)(PhPy)Cl] has pre‐activated 2‐phenylpyridine with a partly developed Ru–H bond. Further, we show that K2CO3 is not directly involved in the C–H activation step and it serves in the reaction as a base. 2‐Phenylpyridine C–H activation catalysed by a ruthenium(II) β‐diketonate complex was studied by ESI‐MS and CID. We have identified [Ru(β‐diketonate)(CTPhPy)Cl]+ as an active intermediate, and its collisional activation leads to C–H activation. DFT calculations were performed to identify all ruthenium intermediates along the C–H activation reaction pathway. [ABSTRACT FROM AUTHOR]