1. Irida-β-ketoimines Derived from Hydrazines To Afford Metallapyrazoles or N-N Bond Cleavage: A Missing Metallacycle Disclosed by a Theoretical and Experimental Study
- Author
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Eider San Sebastian, María A. Garralda, Antonio Rodríguez-Diéguez, Itxaso Bustos, Itziar Zumeta, José M. Seco, Claudio Mendicute-Fierro, and Miguel A. Huertos
- Subjects
Proton ,010405 organic chemistry ,Chemistry ,Stereochemistry ,Electron delocalization ,Metallacycle ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Medicinal chemistry ,Tautomer ,0104 chemical sciences ,Inorganic Chemistry ,Molecule ,Physical and Theoretical Chemistry ,Bond cleavage - Abstract
Unprecedented metallapyrazoles [IrH2{Ph2P(o-C6H4)CNNHC(o-C6H4)PPh2}] (3) and [IrHCl{Ph2P(o-C6H4)CNNHC(o-C6H4)PPh2}] (4) were obtained by the reaction of the irida-β-ketoimine [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNNH2))H}] (2) in MeOH heated at reflux in the presence and absence of KOH, respectively. In solution, iridapyrazole 3 undergoes a dynamic process due to prototropic tautomerism with an experimental barrier for the exchange of ΔGcoal⧧ = 53.7 kJ mol–1. DFT calculations agreed with an intrapyrazole proton transfer process assisted by two water molecules (ΔG = 63.1 kJ mol–1). An X-ray diffraction study on 4 indicated electron delocalization in the iridapyrazole ring. The reaction of the irida-β-diketone [IrHCl{(PPh2(o-C6H4CO))2H}] (1) with H2NNRR′ in aprotic solvents gave irida-β-ketoimines [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNNRR′))H}] (R = R′ = Me (5); R = H, R′ = Ph (8)), which can undergo N–N bond cleavage to afford the acyl–amide complex [IrHCl(PPh2(o-C6H4CO))(PPh2(o-C6H4C(O)N(CH3)2))-κP,κO] (6) o...
- Published
- 2016