Synthesis and Structures of Ruthenium and Iron Complexes Bearing an Unsymmetrical Pincer‐type Ligand with Protic Pyrazole and Tertiary Aminoalkyl Arms

Abstract

AbstractA protic pyrazole‐armed NNN‐type pincer ligand 2‐(5‐tert‐butylpyrazol‐3‐yl)‐6‐(diethylaminomethyl)pyridine (LH) with a tertiary aminomethyl tether was synthesized as a new template for metal‐ligand bifunctional catalysts furnished with proton‐responsive pyrazole and hemilabile amine as the cooperating units. Treatment of LH with trans‐[RuCl2(Me2SO)4] and anhydrous FeCl2 led to the formation of the pincer‐type ruthenium complex [RuCl2(Me2SO‐S)(LH)] (2) and iron complex [FeCl2(LH)] (3), respectively. Detailed structures of 2·CH2Cl2 and 3 were determined by X‐ray crystallography. The Brønsted acidic pyrazole NH group proved to be engaged in intra‐ or intermolecular hydrogen bonding. Catalytic hydrogenation of acetophenone with the protic pincer‐type complexes 2 and 3 was also investigated.