Irida-β-ketoimines Derived from Hydrazines To Afford Metallapyrazoles or N-N Bond Cleavage: A Missing Metallacycle Disclosed by a Theoretical and Experimental Study.
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) or [IrHCl(PPh2(o-C6H4CO))(PPh2(o-C6H4CN)-κP)(NH2NHPh-κNH2)] (9) containing o-(diphenylphosphine)benzonitrile and phenylhydrazine, respectively. From a CH2Cl2/CH3OH solution of 9 kept at -18 °C, single crystals of [IrHCl(PPh2(o-C6H4CO))(PPh2(o-C6H4CN)-κP))(HN═NPh-κNH)] (10) containing o-(diphenylphosphine)benzonitrile and phenyldiazene were formed, as shown by X-ray diffraction. The reaction of 1 with methylhydrazine in methanol gave the hydrazine complex [IrCl(PPh2(o-C6H4CO))2(NH2NH(CH3)-κNH2)] (7). Single-crystal X-ray diffraction analysis was performed on 6 and 7.
Facultad de Química de San Sebastián, Universidad del País Vasco (UPV/EHU) , Apdo. 1072, 20080 San Sebastián, Spain.
Itziar
I
Zumeta
Facultad de Química de San Sebastián, Universidad del País Vasco (UPV/EHU) , Apdo. 1072, 20080 San Sebastián, Spain.
Claudio
C
Mendicute-Fierro
Facultad de Química de San Sebastián, Universidad del País Vasco (UPV/EHU) , Apdo. 1072, 20080 San Sebastián, Spain.
Itxaso
I
Bustos
Facultad de Química de San Sebastián, Universidad del País Vasco (UPV/EHU) , Apdo. 1072, 20080 San Sebastián, Spain.|Ikerbasque, Basque Foundation for Science , 48013 Bilbao, Spain.
Miguel A
MA
Huertos
Facultad de Ciencias, Universidad de Granada , Avda. Fuenteventura s/n, 18071 Granada, Spain.
Antonio
A
Rodríguez-Diéguez
Facultad de Química de San Sebastián, Universidad del País Vasco (UPV/EHU) , Apdo. 1072, 20080 San Sebastián, Spain.
José M
JM
Seco
Facultad de Química de San Sebastián, Universidad del País Vasco (UPV/EHU) , Apdo. 1072, 20080 San Sebastián, Spain.
Eider
E
San Sebastian
Facultad de Química de San Sebastián, Universidad del País Vasco (UPV/EHU) , Apdo. 1072, 20080 San Sebastián, Spain.
María A
MA
Garralda