Mendeleev Commun., 2013, 23, 135–136 – 135 – © 2013 Mendeleev Communications. All rights reserved. Mendeleev Communications The discovery of new types of materials with practically important properties is one of key strategic trends in the development of chemical science and technology. From this point of view the metal-organic frameworks, or coordination polymers, formed by mono- and polynuclear coordination compounds have become important in various research areas. 1–8 Currently, these com- pounds are of great interest due to their potential practical applications, mainly as gas-storage 9–12 and magnetically active 13 materials, and frameworks for catalytic reactions. 14–16 Some zinc(II) 17 and magnesium(II) 18 complexes with azo ligands can be regarded as potential building blocks for photogalvanic elements and optical electronic devices. 19–21 Normally, the structural unit is represented as metal centres connected by organic linkers. Dinuclear complexes of nickel(II), zinc(II), cobalt(II) and man- ganese(II) were found to be important intermediates in biological systems which catalyze hydrolysis of peptide and phosphate ester bonds via formation of O–P–O bridged metal intermediates. 22 These species play a central role in biological processes of oxidative phosphorylation, 23,24 oxidative decarboxylation 25 and energy transduction. 26–28 For example, a 60-fold increase in the rate of hydrolysis of adenosine-5'-triphosphate (ATP) is observed in the presence of Cu II ions, dimeric [Cu 2 (ATP) 2 (OH) 2 ] 6– having been found as an intermediate of the overall process. 29 Further- more, a 10 5 -fold acceleration of hydrolysis of pyrophosphates to orthophosphates occurs at pH 7 in the presence of [Co(DAP) 2- (OH)(H 2 O)] 2+ (DAP = 1,3-diaminopropane) complexes which are converted into dinuclear species. 30 However, a very restricted number of dinuclear metal com- plexes formed by bridging phosphinate {m-O 2 P(H)R} – ligands bearing P–H moiety are currently known. To the best of our know- ledge only aluminum, 31 zinc 32 and nickel 33 dinuclear complexes formed by bridging {m-O 2 P(H)R} – ligands have been synthesized and characterized. The presence of P–H bond in the complex mole- cule can play a central role in its catalytic activity in hydrogena- tion and proton transfer. 34 Moreover, this creates possibility of direct modification of the obtained polymer at phosphorus centre. Herein we describe the synthesis and X-ray crystal structure of new dinuclear cobalt complex {Co 2 [m-O 2 P(H)Mes] 2 (bpy) 4 }Br 2 1 (Mes = 2,4,6-trimethylphenyl, bpy = 2,2'-bipyridine), representing the first example of dinuclear cobalt complex formed by bridg- ing mesitylphosphinate ligands. Complex 1 was prepared from 2,4,6-trimethylphenylphosphinic acid, 33,35,36 cobalt dibromide hexahydrate and 2,2'-bipyridine in DMF (Scheme 1). The reactants were dissolved in DMF for 2 h, then the auto- clave temperature was raised to 120 °C within 5 h, and the process was run at this temperature for 25 h. After slow (20 h) cooling of the autoclave to room temperature the crystals of 1 suitable for X-ray analysis were obtained in 68% yield. † Note that pro- cessing at room temperature does not give complex 1 cleanly. According to single-crystal X-ray diffraction, ‡ cobalt complex 1 forms centrosymmetric dimer in which the two Co atoms are Synthesis, X-ray crystal structure and quantum-chemical study of new dinuclear cobalt complex {Co 2 [ m-O 2 P(H)Mes] 2 (bpy) 4 }Br 2 Ekaterina A. Trofimova, a Alexey B. Dobrynin, a Tatiana P. Gerasimova, a Sergey A. Katsyuba, a Oleg G. Sinyashin a and Dmitry G. Yakhvarov* a,b a A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, 420088 Kazan, Russian Federation. Fax: +7 843 273 2253; e-mail: yakhvar@iopc.ru b A. M. Butlerov Institute of Chemistry, Kazan (Volga Region) Federal University, 420008 Kazan, Russian Federation. Fax: +7 843 238 7901 05.004 DOI: 10.1016/j.mencom.2013. The reaction of cobalt dibromide hexahydrate with 2,2'-bipyridine (bpy) and mesitylphosphinic acid MesP(O)(OH)H (Mes = = 2,4,6-trimethylphenyl) under solvothermal synthesis conditions leads to a new dinuclear cobalt(II) complex {Co 2 [m-O 2 P(H)Mes] 2 - (bpy) 4 }Br 2 formed by two bridging {m-O 2 P(H)Mes} – ligands. X-ray crystal structure analysis of the complex displayed that cobalt ions have distorted octahedral coordination and are doubly bridged by two mesitylphosphinato ligands. † For detailed procedure and characteristics of complex 1, see Online Supplementary Materials. ‡ Crystal data for 1: brown-yellow crystals, C 58 H 56 Co 2 N 8 O 4 P 2 ·Br 2 (M = = 1268.73), monoclinic, space group P2 1 /c, at 150(2) K: a = 11.938(2), b = 15.037(3) and c = 17.045(3) Å, b = 109.478(2)°, V = 2884.9(8) Å 3 , Z = 2, d calc = 1.461 g cm –3 , m = 2.068 mm –1 , R int = 0.033, q max = 27.0°. Bruker Smart Apex II CCD diffractometer, 24 046 reflections collected, 5382 observed reflections with I > 2s (I), final R = 0.0271, wR 2 = 0.0658, 6287 independent reflections with F 2 ³ 2s (I), S = 1.03. CCDC 930228 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. For details, see ‘Notice to Authors’, Mendeleev Commun., Issue 1, 2013. 2 CoBr 2 + 4 bpy + 2 MesP(O)(OH)H 1 – 2 HBr N N N N Co O P H O O P O H N N N N Co 2+ Me Me Me Me Me Me 2 Br Scheme 1