1781 ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2007, Vol. 52, No. 11, pp. 1781–1785. © Pleiades Publishing, Inc., 2007. Original Russian Text © T.M. Ivanova, A.V. Naumkin, A.A. Sidorov, M.A. Kiskin, V.M. Novotortsev, I.L. Eremenko, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 11, pp. 1892–1896. Polynuclear transition metal carboxylate complexes with amines have different structures and a wide spec- trum of chemical and physical (first of all, magnetic) properties [1]. The diversity of the structures of these complexes is determined by the structures of ligands and the properties of their donor atoms, as well as by the specific features of the electronic structure of metal ions. Due to this diversity, it is possible to obtain the entire set of coordination environments comprising oxygen and nitrogen atoms. Semidiamine and ami- doamine complexes exemplify a pure nitrogen environ- ment. High-spin transition metal carboxylate com- plexes are of interest to researchers because of the pos- sibility of varying their magnetic properties as a function of their molecular structure and because of their unique chemical and physical properties, which make them suitable candidates for use in catalysis, enzymology, and magnetochemistry, as well as for preparation of drugs [2]. X-ray photoelectron spectroscopy (XPS) is used for studying the physical properties of complexes and their electronic structure. XPS data on the electron density redistribution in molecules upon structural changes can shed light on the relationship between the structure and the physical, chemical, and autocatalytic properties of compounds [3–5]. XPS has provided valuable informa- tion on the stereostructure of transition metal com- plexes [6–8]. However, until very recently, this method was virtually unused for studying the electronic struc- ture of polynuclear transition metal carboxylate com- plexes. The first XPS studies dealt with polynuclear cobalt complexes [9, 10]. The present work is aimed at studying by XPS the electronic structure of nickel tri- methylacetate complexes with different mono- and bidentately coordinated amines. EXPERIMENTAL The X-ray photoelectron spectra of compounds were recorded on a Thermo VG Scientific Sigma Prober spectrometer. An aluminum anode (AlK α radia- tion, 1486.6 eV) was used as the excitation source. Each spectral line was approximated with a Gaussian profile or their sum, and the background caused by sec- ondary electrons and photoelectrons that lose energy was approximated by a straight line. Measurements were repeated at least twice at a pressure of ~10 –9 Torr. The spectra were recorded at room temperature. The spectra were calibrated using the ë1s peak, assuming the binding energy (E b ) of the component correspond- ing to C–(C,H) bonds to be 285.0 eV. To do this, the spectra were decomposed into components according to the structural formulas, which were obtained by X-ray crystallography. The basic binding energies of the functional groups contained in the samples were taken from [11]. As in the case of cobalt complexes [10], reliable determination of the binding energies of the levels under consideration presents a serious prob- lem since compensation for surface charging caused by X-ray radiation is required. For higher reliability of X-ray Photoelectron Spectra and Structure of Polynuclear Nickel Complexes T. M. Ivanova a , A. V. Naumkin b , A. A. Sidorov a , M. A. Kiskin a , V. M. Novotortsev a , and I. L. Eremenko a a Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991 Russia b Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ul. Vavilova 28, Moscow, 119991 Russia Received March 22, 2007 Abstract—Mono- and binuclear nickel complexes of different stoichiometry have been studied by X-ray pho- toelectron spectroscopy (XPS). The Ni2p, Ni3p, and N1s X-ray photoelectron spectra have been examined, and the role of a ligand in their formation has been determined. As distinct from a low-spin Ni(II) complex, the Ni2 spectra of high-spin Ni(II) compounds show strong satellite lines. For high-spin Ni(II) complexes, which have unpaired 3d electrons, the Ni2 1/2 –Ni2 3/2 spin–orbit splitting is larger than that for a low-spin Ni(II) com- pound. The presence or absence of the satellite structure has made it possible to classify these complexes with regard to their magnetic properties. The difference between the Ni2 3/2 and N1s binding energies has made it possible to estimate the covalence of the metal–ligand bond. The XPS results are consistent with X-ray crystal- lography data. DOI: 10.1134/S003602360711023X PHYSICAL METHODS OF INVESTIGATION