Adducts of Bis(hexafluoroacetylacetonato)metal(II) with Uni-and Bidentate Nitrogenous Bases

Abstract Base adducts of the types: M(hfa)2(py)2, M(hfa)2phen, and M(hfa)2bpy [M=Co(II), Ni(II), Cu(II), and Zn(II); Hhfa=hexafluoroacetylacetone; py=pyridine; phen=1,10-phenanthroline; bpy=2,2′-bipyridine] were prepared, and their infrared spectra were examined in detail. These adducts have a cis-octahedral configuration except for Ni(hfa)2(py)2. The metal-oxygen stretching frequencies of the adducts in the 405–370 cm−1 region decrease along the series: nickel(II)>cobalt(II)>copper(II)>zinc(II). Adduct formation leads to the marked weakening of Cu–O bonds in the copper(II) adducts, which is ascribable to the equatorial ligation of the neutral bases. The mass spectral studies of M(hfa)2phen and M(hfa)2bpy revealed that the addition of a neutral ligand affects the fragmentation of the complex remarkably. The exceptional behavior of Cu(hfa)2phen under electron impact is explained in terms of the tendency of copper(II) ion to undergo valency change.