New Binding Modes of 1‐Acetyl‐ and 1‐Benzoyl‐5‐hydroxypyrazolines – Synthesis and Characterization of O,O′‐Pyrazoline‐ and N,O‐Pyrazoline‐Zinc Complexes

Abstract

The 1-acetyl-and 1-benzoyl-5-hydroxypyrazolines 1a [3, , 1-C(=O)CH 3 ], 1b [3, , 1-C(=O)CH 3 ] and 1c [3, , 1-C(=O)C 6 H 5 ] have been synthesized in good yields and characterized by X-ray crystallography. The 1-acetyl-and 1-benzoyl-5-hydroxypyrazoline ligands were treated with dimethylzinc in a 1:1 molar ratio to form complexes 8 with a RO-Zn-Me motif. These complexes are accessible by simple Brønsted acid-base reactions generating methane as a side product. Characterization of complexes 8a and 8c by X-ray crystallography revealed a dimeric structure in the solid state. The two subunits generate a Zn 2 O 2 square. The acetyl and benzoyl functionality of the ligands coordinate to the metal to span a six-membered ring. Moreover, the coordination mode of the ligand can be easily influenced by the ad-

Reductive Cleavage of Amides to Alcohols and Amines Catalyzed by Well‐Defined Bimetallic Molybdenum Complexes

“…[10] In accordance with a previously established protocol, we were able to synthesize disubstituted complexes [{Mo(1-H)-A C H T U N G T R E N N U N G (OtBu) 2 } 2 ] (4) and [{Mo(2-H)A C H T U N G T R E N N U N G (OtBu) 2 } 2 ] (5) in 48-75 % yield by direct protolysis of 3 (Scheme 1). [8,11] 1 H, 19 F, and 13 C NMR investigations of these diamagnetic complexes confirmed the desired double substitution and successful coordination to the triple bond (see Supporting Information).…”

Application of Nickel Complexes Modified by Tridentate O,N,O′‐Ligands as Precatalysts in Nickel‐Catalyzed C(sp2)–C(sp3) Bond Formations

“…We have recently investigated the potential of 1‐acetyl‐ and 1‐benzoyl‐5‐hydroxypyrazoline ligands in coordination chemistry (Figure 1). 8 Depending on the metal precursor and the reaction conditions, different coordination modes were feasible. In the case of nickel, 5‐hydroxypyrazoline ligands were coordinated in a tridentate O , N , O′ ‐coordination mode as reported by Joshi and co‐workers (Figure 1; 4 ) 9,11.…”

Nickel complexes with a O,N,O′-ligand and a phosphane co-ligand – Monometallic versus bimetallic complexes

“…For instance, the flexibility of the ligand precursor 1 was shown in the reaction with ZnMe 2 . On the one hand, an O,O 0 -coordination after deprotonation was observed, while the addition of base revealed a second deprotonation and a O,N-coordination [5,6]. A similar O,O 0 -motif was observed for coordination to molybdenum, resulting in attractive precatalysts for the reduction of organic amides to amines [7].…”