New co-ordination compounds derived from barium(II) and the anionic 4-tert-butylacetyl-3-methyl-1-phenylpyrazol-5-onate ligand (Q–). Crystal and molecular structure of [Ba2Q4(H2O)4], [Ba2Q4(Him)4], [BaQ2(tetraglyme)] (tetraglyme = 2,5,8,11,14-pentaoxapentadecane) and [BaQ2(phen)2]
Abstract
By reaction of 4-tert-butylacetyl-3-methyl-1-phenylpyrazol-5-one (HQ) with metallic Ba in MeOH the dinuclear derivative [{BaQ2(H2O)2}2] 1 has been synthesized. It contains two barium atoms each eight-co-ordinated by a terminal bidentate Q ligand, two bridging double chelating Q ligands and two molecules of water. When the reaction of HQ with Ba was carried out in the presence of mono-, bi- or poly-dentate O- or N-donor ligands, derivatives of formula BaQ2Ln(H2O)m have been obtained, depending on the nature of the ancillary ligand and reaction conditions employed [L = 2,5,8,11,14-pentaoxapentadecane (tetraglyme), 2,5,8,11-tetraoxadodecane (triglyme), 2,5,8-trioxanonane (diglyme), 2,2′∶6′,2″-terpyridine (terpy), 2,3-bis(2-pyridyl)pyrazine (Pypy), n = 1, m = 0 or 1; L = imidazole (Him), 1-methylimidazole (1-MeIm), 2-methylimidazole (2-MeImH), 1,10-phenanthroline (phen), 2,2′-bipyridyl (bipy), 2,9-dimethyl-1,10-phenanthroline (Cupr) and triphenylphosphine oxide (PPh3O), n = 2, m = 0 or 1]. In the nine-co-ordinated [BaQ2(tetraglyme)] the Ba atom is co-ordinated by all the five oxygen atoms of tetraglyme and by four oxygen atoms of two bidentate Q whereas the co-ordination number of barium in [BaQ2(phen)2] is eight due to four oxygen atoms of the two Q ligands and four nitrogen atoms of the two 1,10-phenanthrolines. The derivative [{BaQ2(Him)2}2] is dinuclear with the Ba atoms linked by two double chelating Q ligands. The imidazoles complete the co-ordination number of Ba to 8. The compound [(BaQ2)n] has been obtained by heating derivative 1 in vacuo at 100 °C, whereas the 1∶1 adduct [BaQ2(phen)] was obtained only when [(BaQ2)n] was treated in diethyl ether with an equimolar solution of phen. When a methanol solution of [BaQ2(Pypy)] reacts with an equimolar methanol solution of CdCl2 scrambling of the ligand occurs and derivatives 1 and [(CdCl2)2(Pypy)] are obtained. All the compounds obtained have been characterised by IR and far-IR data, conductivity and vaporimetric molecular weight measurements, 1H NMR and in some cases also variable temperature 1H NMR spectra. Comparison was made with structural and spectroscopic data reported for related barium(II) compounds.