ISSN 1063-7745, Crystallography Reports, 2011, Vol. 56, No. 5, pp. 842–847. © Pleiades Publishing, Inc., 2011. Original Russian Text © I.E. Evstifeev, M.A. Kiskin, A.S. Bogomyakov, A.A. Sidorov, V.M. Novotortsev, I.L. Eremenko, 2011, published in Kristallografiya, 2011, Vol. 56, No. 5, pp. 900–905. 842 INTRODUCTION Coordination polymers are specific coordination compounds that consist of repetitive metal-containing fragments connected by organic polyfunctional ligands into one-, two-, or three-dimensional archi- tectures [1–8]. Such polymeric systems attract the attention of researchers due to their unusual physical and chemical properties [3, 9–12]. One of the main problems encountered when working with these com- pounds is their synthesis [13]. Nowadays, high- dimensional architectures are usually obtained by the self-assembly of simple components, i.e., salts of met- als and organic polyfunctional ligands [14–18]. The solubility and purity of compounds thus obtained are often far from desired. In some cases the use of deriv- atives of carboxylic acids containing bulky substituents as one of the components of self-assembly noticeably improves the solubility of the resulting coordination polymers in organic solvents. This allows one to solve the problem of purification by means of recrystalliza- tion, although such attempts are not necessarily suc- cessful. The derivatives of the pivalic acid that are used in our works allow us to synthesize polynuclear struc- tures, isolate them in the crystal form, and study their chemical transformations in organic solutions. These studies are of importance because they make it possi- ble to directionally affect the starting architecture of coordination polymers and to form the desired metal skeletons of molecules. In this work two types of starting coordination polymers containing high-spin Co(II) atoms (S = 3/2)— {[Co 5 (OH 2 )(OH)( Piv) 9 ( L 1 ) 4 ] · 0.5HPiv · L 1 } n (I) and {[Co 2 (OH 2 )(Piv) 4 (L 2 ) 2 ] · MeCN} n (II), where Piv – is the pivalate anion, L 1 is pyrazine, and L 2 is pyrimidine [19]—were treated with lithium pivalate with the aim of obtaining magneti- cally diluted polymeric structures, including cobalt(II) and lithium atoms. EXPERIMENTAL Starting complexes {[Co 5 (OH 2 )(OH)( Piv ) 9 ( L 1 ) 4 ] · 0.5HPiv · L 1 } n ( I ) and {[Co 2 (OH 2 )(Piv) 4 (L 2 ) 2 ] · MeCN} n (II) were obtained by the procedures in [19]. Lithium pivalate was synthesized by a reaction of equimolar aqueous solutions of LiOH (reagent grade) and HPiv (Alfa Aesar). The resulting solution was dried, and the solid phase was washed with hexane. The MeCN that was used in the synthesis of new complexes was not purified additionally. The microprobe analysis of the compounds was performed on a Carlo Erba analyzer. Synthesis of {[Li 2 Co 2 (Piv) 6 (L 1 ) 2 ] · 2MeCN} n (III) LiPiv(0.07 g, 0.64 mmol) was added to a solution of I (0.2 g, 0.12 mmol) in MeCN (30 ml). The reaction mixture was stirred upon heating (80°С) for 40 min. The blue solution was separated from unreacted LiPiv by filtration and allowed to stand at room temperature for 24 h. As a result, pink crystals of X-ray quality pre- cipitated. They were isolated from the solution by decantation, washed with cold MeCN, and dried in air. The yield of III was 75% (0.22 g). For C 42 H 68 Co 2 Li 2 N 6 O 12 anal. calcd. (%): C, 51.43; H, 6.99; N, 8.57. STRUCTURE OF ORGANIC COMPOUNDS Structure and Magnetic Properties of Heterometallic Coordination Carboxylate Polymers with Cobalt and Lithium Atoms I. E. Evstifeev a , M. A. Kiskin a , A. S. Bogomyakov b , A. A. Sidorov 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 e-mail: mkiskin@igic.ras.ru b International Tomography Center, Siberian Branch, Russian Academy of Sciences, ul. Institutskaya 3a, Novosibirsk, 630090 Russia Received March 22, 2011 Abstract—Reactions between lithium pivalate and cobalt coordination polymers [Co 5 (OH 2 )(OH)(Piv) 9 )L 1 ) 4 ] n (I) and [Co 2 (OH 2 )(Piv) 4 (L 2 ) 2 ] n (II), where Piv—is the pivalate anion, L 1 is pyrazine, and L 2 is pyrimidine, result in new heterometallic polymers {[Li 2 Co 2 (Piv) 6 (L 1 ) 2 ] 2 MeCN} n (III), {[Li 2 Co 2 (Piv) 6 (L 2 )] 0.5 MeCN} n (IV), and [Li 2 Co 2 (Piv) 6 (L 2 ) 2 ] n (V). The resulting compounds contain tetra- nuclear {Li 2 Co 2 (Piv) 6 } fragments connected by neutral bridging ligands (pyrazine or pyrimidine) into layer structures. Crystal structures III–V are determined, and the magnetic properties of III and IV are studied. DOI: 10.1134/S1063774511050087