X-ray photoelectron spectra of metal complexes of substituted 2,4-pentanediones

The X-ray photoelectron spectra of 14 complexes of Al³⁺, Cr ³⁺, Fe³⁺, Co³⁺ and Cu²⁺ with 3-X-2,4-pentanedione (X = H, Cl, Br) were determined to analyse the nature of metal-ligand bonding in these complexes. The trend in the position of np photoelectron lines of X-group with a change of metal ion was decided by the relative contribution of metal-toligand and ligand-to-metal charge transfer. The analysis of the satellites in the M(2p_3/2) and M(2p_1/2) spectra suggested that the metal-ligand bond in the chromium(III) complex had higher covalent character than that in the iron(III) complex. The satellite separations in the O(1s) spectra of M(3-Xptdn)₃ were in the range 4.0-4.8 eV: these satellites were assigned to a shake-up transition of Lπ → Lπ^* character. The O(1s) spectra of Fe(3-Xptdn)₃ and A1(3-Xptdn)₃ displayed an additional strong peak to higher energy than that of the main peak (δE = 2.1–3.1 eV) when the samples of complexes were bombarded with argon ions for a longer time.