Copper(II) Complexes of 3,4,5‐Trisubstituted Pyrazolates: In Situ Formation of Pyrazole Rings from Different Carbon Centers |
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| Authors: | Oindrila Das Tanmay Malakar Arghya Mandal Dr Ankan Paul Dr Tapan Kanti Paine |
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| Institution: | 1. Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2?A and 2?B Raja S. C. Mullick Road, Jadavpur, Kolkata‐700032 (India);2. Raman Center for Atomic Molecular and Optical Sciences, Indian Association for the Cultivation of Science, 2?A and 2?B Raja S. C. Mullick Road, Jadavpur, Kolkata‐700032 (India), Fax: (+91)?33‐2473‐2805 |
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| Abstract: | The synthesis and characterization of two pyrazolate‐bridged dicopper(II) complexes, Cu2(L1)2(H2O)2](ClO4)2 ( 1 , HL1=3,5‐dipyridyl‐4‐(2‐keto‐pyridyl)pyrazole) and Cu2(L2)2(H2O)2](ClO4)2 ( 2 , HL2=3,5‐dipyridyl‐4‐benzoylpyrazole), are discussed. These copper(II) complexes are formed from the reactions between pyridine‐2‐aldehyde, 2‐acetylpyridine (for compound 1 ) or acetophenone (for compound 2 ), and hydrazine hydrate with copper(II) perchlorate hydrate under ambient conditions. The single‐crystal X‐ray structure of compound 1? 2 H2O establishes the formation of a pyrazole ring from three different carbon centers through C? C bond‐forming reactions, mediated by copper(II) ions. The free pyrazoles (HL1 and HL2) are isolated from their corresponding copper(II) complexes and are characterized by using various analytical and spectroscopic techniques. A mechanism for the pyrazole‐ring synthesis that proceeds through C? C bond‐forming reactions is proposed and supported by theoretical calculations. |
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| Keywords: | copper density functional calculations pyrazole solid‐state structures synthetic methods |
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