Heterobinuclear cryptates; cooperative binding generates two different coordination sites within a symmetrical cryptand

On binding a stereochemically demanding cation a symmetrical cryptand host generates a second non-identical site thereby offering a reliable route to certain types of heterobinuclear cryptates. Specifically, mononuclear complexes [(CoL)-L-II](BF4)(2) (1) and [(CuL)-L-II](BF4)(2) (2), of the symmetrical cryptand L [formed by the 3+2 condensation of 3,6-diformylpyridazine with tris(2-aminoethyl)amine (tren)], were reacted with 1 equiv. of Cu(MeCN)(4)BF4 to yield [(CoCuL)-Cu-II-L-I](BF4)(3) (3) and [(CuCuL)-Cu-II-L-I](B3F4)(3) 4, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.