ORIGINAL PAPER Crystal Structure of Cs 4 [{(C 6 H 6 )Ru} 2 Nb 6 O 19 ]Á8MeOHÁ2H 2 O. Structural Overview of Hybrid Organometallic Hexametalates of Niobium and Tantalum: Alkali Metal Coordination Behavior Pavel A. Abramov 1,2 • Tatiana P. Zemerova 1,2 • Maxim N. Sokolov 1,2,3 Received: 7 August 2016 Ó Springer Science+Business Media New York 2016 Abstract Reaction of Cs 8 [Nb 6 O 19 ]Á14H 2 O with [(C 6 H 6 )RuCl 2 ] 2 leads to the formation of trans-[{(C 6 H 6 )Ru} 2 Nb 6 O 19 ] 4- (1). Evaporation of the reaction solution and extraction into methanol (MeOH) yielded Cs 4 [{(C 6 H 6 )Ru} 2 Nb 6 O 19 ]Á8MeOHÁ2H 2 O(1a) as main product together with a small amount of Cs 4 [{(C 6 H 6 )Ru} 2 Nb 6 O 19 ]Á4MeOHÁ6H 2 O(1b), both characterized by X-ray analysis. These structures complete a set of known organometallic polyoxoniobate or polyoxotantalate complexes [{Cp*M 0 } x M 6 O 19 ] n- and [{(C 6 H 6 )Ru} x M 6 O 19 ] n- (M = Nb, Ta; M 0 = Rh, Ir; x = 1, 2; n = 6, 4; Cp* = g 5 -C 5 (CH 3 ) 5 ) and give additional information about the importance of cation–anion interac- tions in the crystal structures of such complexes. Keywords Hexaniobate Á Caesium Á Ruthenium Á Methanol Á Alkali metal coordination Á X-ray structures Introduction The chemistry of polyoxoniobates and tantalates is one of the youngest areas in a very wide field of polyoxometalates, which play significant role in modern coordination chemistry [1], catalysis [2], magnetochemistry [3], biochemistry [4] etc. The solution behavior of polyoxoniobates and tantalates is very sensitive to the nature of counter Electronic supplementary material The online version of this article (doi:10.1007/s10876-016-1116-6) contains supplementary material, which is available to authorized users. & Pavel A. Abramov abramov@niic.nsc.ru 1 Nikolaev Institute of Inorganic Chemistry SB RAS, 3 Akad. Lavrentieva Ave, 630090 Novosibirsk, Russia 2 Novosibirsk State University, ul. Pirogova 2, 630090 Novosibirsk, Russia 3 Kazan Federal University, 18 ul. Kremlyovskaya, 420008 Kazan, Russia 123 J Clust Sci DOI 10.1007/s10876-016-1116-6