New Copper Complexes with N,O-Donor Ligands Based on Pyrazole Moieties Supported by 3-Substituted Acetylacetone Scaffolds.

The new 3-monosubstituted acetylacetone ligands, 3-(phenyl(1-pyrazol-1-yl)methyl)pentane-2,4-dione (HL) and 3-((3,5-dimethyl-1-pyrazol-1-yl)(phenyl)methyl)pentane-2,4-dione (HL), were synthesized and used as supporting ligands for new copper(II) and copper(I) phosphane complexes of the general formulae [Cu(HL)(L)] and [Cu(PPh)(HL)]PF (X = Pz (pyrazole) or PzMe (3,5-dimethylpyrazole)), respectively. In the syntheses of the Cu(I) complexes, the triphenylphosphine coligand (PPh) was used to stabilize copper in the +1 oxidation state, avoiding oxidation to Cu(II). All compounds were characterized by CHN analysis, H-NMR, C-NMR, FT-IR spectroscopy, and electrospray ionization mass spectrometry (ESI-MS). The ligands HL () and HL () and the copper complex [Cu(PPh)(HL)]PF () were also characterized by X-ray crystallography. The reactivity of these new compounds was investigated and the new compounds 4-phenyl-4-(1-pyrazol-1-yl)butan-2-one () and 4-(3,5-dimethyl-1-pyrazol-1-yl)-4-phenylbutan-2-one () were obtained in basic conditions via the retro-Claisen reaction of related 3-monosubstituted acetylacetone, providing efficient access to synthetically useful ketone compounds. Compound was also characterized by X-ray crystallography.