DOI: 10.1002/chem.201101646 Sodium and Potassium Salts of Mono- and Dianionic a-Iminopyridines Hari Pada Nayek, [a, b] Nicholas Arleth, [a] Ina Trapp, [a] Matthias Lçble, [a] Pascual OÇa-Burgos, [a] Magdalena Kuzdrowska, [a, c] Yanhua Lan, [a] Annie K. Powell, [a] Frank Breher,* [a] and Peter W. Roesky* [a] a-Diimine (1,4-diaza-1,3-butadiene) ligands are well es- tablished in main-group, transition-metal, and lanthanide chemistry. [1–7] Beside their application as ligands for late- transition-metal complexes, which can function as active and selective catalysts for a-olefin polymerization, [8] a-diimine and related ligands are of special interest due to their ability to undergo redox chemistry. [9] They have frequently been described as “non-innocent” ligands. [10–12] For example, in lanthanide chemistry, it has been found that the formal oxi- dation state of Eu [13] and Yb [14] depends on the nature of the substituents on the a-diimine ligand and on the ligand on the metal center. Thus, in both cases, the a-diimine acts either as neutral ligand or as radical anion. Reduction of a- diimines, using either alkali metals or electrochemical meth- ods, leads in each case to the corresponding radical anions [15–18] and eventually to diamagnetic dianions, [17–24] albeit at much more negative potentials. In contrast to the well-established chemistry of a-di- imines, the related a-iminopyridines are much less investi- gated. The three different redox states of a-iminopyridines are shown in Scheme 1. The neutral system L 0 has been ex- tensively used as ligand for late transition metals. [4, 25–29] Only recently, the monoanion LC  and the doubly reduced dianion L 2 were investigated as ligands in more detail. Recent re- ports showed a series of bis(a-iminopyridine)–metal com- plexes featuring aluminum [30] and the first-row transition ions (Cr, Mn, Fe, Co, Ni, and Zn) [31, 32] with the monoanionic, and thus paramagnetic p-radical form of the ligand in coor- dination complexes. The a-iminopyridine N-2,6-diisopropyl- phenylimino-2-pyridine (IPy) has also been introduced in lanthanide chemistry. [33, 34] In this context, a potassium deriv- ative of the monoanionic form of a-iminopyridine was pre- pared in situ, but not further characterized. [34] The doubly reduced dianion has only been observed in two magnesium complexes so far. [35] In contrast, the reaction of “GaI” with a-iminopyridine leads to reductive coupling of the coordi- nated ligand to give neutral diamido-digallium complexes. [36] Based on this information, we were interested in a compre- hensive study of the properties of the alkali metal salts of the monoanionic p-radical and the doubly reduced dianion of a-iminopyridine in solution and in the solid state. We report here the synthesis, characterization and magnetic properties of sodium and potassium salts of the mono- and dianionic a-iminopyridines. N-2,6-Diisopropylphenylimino-2-pyridine (IPy) was pre- pared according to literature procedures. [37] As a first entry point, we examined the electrochemical properties of IPy using cyclic voltammetry at room temperature in THF. As can be seen from Figure 1, we detected a quasi-reversible one-electron reduction process centered at E 0 1=2 = 2.57 V (vs. the ferrocene/ferrocenium couple, Fc/Fc + ), with a peak- to-peak separation of 158 mV and i pa /i pc  1. It is reasonable to assume that this reduction process furnishes the radical anion LC  . In addition, we observed two irreversible reduc- tion processes at more negative values of E pc = 3.12 and 3.44 V, respectively. Based on these data we speculated that reactions of IPy with alkali metals should yield the radical anion LC  and eventually the dianion L 2 . Indeed, the reaction of IPy with one equivalent of metallic potassium in THF or diethyl ether resulted in the formation of dimeric, p-radical mono- anionic potassium salts [{KACHTUNGTRENNUNG(thf) 2 IPy} 2 ] (1) and [{K- ACHTUNGTRENNUNG(Et 2 O)IPy} 2 ](2), respectively (Scheme 2). As evidenced by NMR spectroscopy, an excess of potassium surprisingly does [a] Dr. H.P. Nayek, Dipl.-Chem. N. Arleth, Dipl.-Chem. I. Trapp, Dipl.-Chem. M. Lçble, Dr. P. OÇa-Burgos, M.Sc. M. Kuzdrowska, Dr. Y. Lan, Prof. Dr. A. K. Powell, Prof. Dr. F. Breher, Prof. Dr. P. W. Roesky Institut für Anorganische Chemie Karlsruhe Institute of Technology (KIT) Engesserstrasse 15, 76131 Karlsruhe (Germany) Fax: (+ 49) 721-6084-4854 E-mail : breher@kit.edu roesky@kit.edu [b] Dr. H. P. Nayek Present address: Department of Applied Chemistry Indian School of Mines, Dhanbad-826004 (India) [c] M. Sc. M. Kuzdrowska Helmholtz Research School Energy-Related Catalysis Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201101646. Scheme 1. Different redox state of a-iminopyridines. [31]  2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Eur. J. 2011, 17, 10814 – 10819 10814