This work has been digitalized and published in 2013 by Verlag Zeitschrift für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namensnennung 4.0 Lizenz. Structure of a Cs(18-crown-6)N(CN)2*H20 Complex: Assembly of the Dimeric 2:2 Anion Paired Encapsulate by Means of jz2-Bridging Water Molecules Julia A. Rusanova3 *, Philip J. Squattritob, Konstantin V. Domasevitcha, VolodimirN. Kokozaya a Department of Inorganic Chemistry, Kiev University, Volodimirskaya St. 64, Kiev 252033, Ukraine b Department of Chemistry, Central Michigan University, Mt. Pleasant, MI 48859, USA Z. Naturforsch. 54 b, 389-393 (1999); received October 23, 1998 18-Crown-6, Caesium Macrocyclic Complexes, Dicyanamide, Crystal Structure The new macrocyclic complex of composition Cs(18-crown-6)N(CN)2-H20 has been pre pared and characterized by X-ray crystallography (monoclinic, space group P2 1In, with a = 11.218(3), b = 8.563(7), c = 21.704(2) Ä; ß = 92.66(1)°, V = 2083(2) Ä3, Z = 4; final R = 0.034 and Rw = 0.038 for 2529 independent reflections with I > 3cr(I)). The complex adopts a molecular dimeric array [Cs(18c6)(^r-H20){N(CN)2}]2(2:2 anion-paired encapsulate). The dimerization of Cs(18c6)+ moieties takes place surprisingly not via the nitrilic nitrogen atoms, but via the water molecules (Cs-0 3.139(5), 3.334(5) A), which is an unprecedented example in the chemistry of M(18c6)+ complexes. The caesium atom adopts nine-fold coordination (Cs-0 (ether) 3.099(5) - 3.280(5) A). One cyano group of the counter anion completes the coordina tion environment of the caesium atom (Cs-N 3.420(8) A), while the second one is involved in hydrogen bonding. Introduction The ability of macrocyclic polyethers (crown ethers), in particular 18-crown-6 (18c6), to form sta ble complexes with alkali metal ions is well known and the M+-18-crown-6 systems have been exam ined in solution as well as in the solid state [ 1 ]. X-ray studies have shown a remarkable variety of structures of different stoichiometry M+-18c6, in cluding 1:1 encapsu- lates [MUScö^-'sandwiches [M(18c6)2]+ [1], club sandwiches [M2(18c6)3]+[2], bimetallic compounds [M2(18c6)]2+, and more complex derivatives [1]. In spite of the fact that the formation of dimeric 2:2 anion-paired encap sulates is a characteristic feature of assembly in the system M(L)+ - X- (M = Rb, Cs; L = crown ether of the 18c6-cavity size), see Scheme 1. The chemistry of such complexes is relatively poorly developed and actually all of the early compounds of this type include NCS~ as a counter anion [1]. Perhaps surprisingly, the recently reported struc ture of the molecular complex [Cs( 1 8 c 6 )l 3 ]2 shows the “classic” example of a dimeric 2:2 anion-paired * Reprint requests to J. A. Rusanova; Fax: +380 44 296 2467, E-mail: kokozay@chem.kiev.ua. encapsulate with central four-membered M 2 X2 ring [3]. Judging by the common charge and linear structure of the NCS“ and I3 - anions, this anal ogy should not be considered so unusual. More over, it serves to underscore the important influence of the nature of the counter anion (shape, size and charge) on the assembly in the system M+-18c6 - anion [1,4]. Another important analogy in SCN- Cs2-NCS and I-I-I-Cs2 -I-I-I linkages are the Lewis base softness and the very weak nucleophilic prop erties of the “tail” sulfur and iodine atoms, which thus, probably, cannot sense electrophilic effects (coordination or hydrogen bonding) leading to com plications in the structure. It is evident therefore, that even a close structural analog of NCS~, the well known representative of the pseudohalide fam ily dicyanamide N(CN)2~ [5] will form a different 0932-0776/99/0300-0389 $ 06.00 © 1999 Verlag der Zeitschrift für Naturforschung, Tübingen • www.znaturforsch.com K