Barium acylpyrazolonate derivatives stabilized by O- and N-donor ligands: synthesis, spectral and structural characterization

New Ba acylpyrazolonate derivatives of formula [Ba(Q)2(tetraglyme)] (HQ = HQtbu = 1-Ph-3-Me-4-C(double bond; length as m-dashO)CH2But-5-pyrazolone; tetraglyme = 2,5,8,11,14-pentaoxapentadecane), [Ba(Q)2(tmeda)2] (HQ = HQtbu or HQpiv, where HQpiv = 1-Ph-3-Me-4-C(double bond; length as m-dashO)But-5-pyrazolone; tmeda = N,N,N′,N′-tetramethylethylenediamine), [Ba(Q)2(pmdien)(H2O)] (HQ = HQtbu or HQpiv; pmdien = N,N,N′,N″,N″-pentamethyldiethylenetriamine) and [Ba(Q)2(pmdien)(Meim)] (HQ = HQtbu or HQpiv; Meim = 1-methylimidazole) have been synthesized and analytically and spectroscopically characterized. They are mononuclear air and solution stable compounds containing an eight-coordinated barium atom. The X-ray crystal structures of the hydrates [Ba(Qtbu)2(pmdien)(H2O)] and [Ba(Qpiv)2(pmdien)(H2O)] show the water molecule directly bonded to Ba and involved in intermolecular H-bonding network. In the X-ray crystal structure of [Ba(Qpiv)2(pmdien)(Meim)], the Meim ligand substitutes the water of previous derivatives and decreases the strength of intermolecular interactions, lowering the melting point. The derivative [Ba(Qtbu)2(pmdien)(NEt3)] has been prepared from interaction of [Ba(Qtbu)2(pmdien)(H2O)] with excess triethylamine in acetonitrile.