1.4.8.11- tetraazacyclotetradecane synthesis

H. Stephan, A. Rohrich, S. Noll, J. Steinbach, R. Kirchner, and J. Seidel, Carbohydratation of 1,4,8,11-tetraazacyclotetradecane (cyclam) Synthesis and binding properties toward concanavalin A, Tetrahedron Lett., 48 (2007) 8834-8838. 

Mercury has the electronic configuration (Xe)4/145d106s2. The first three ionization potentials are 10.43, 18.65 and 34.4 eV, therefore under chemically significant conditions no more than two electrons are removed from the mercury atom. Only one complex of mercury (III), with d9 configuration and a half-life of 5 s at -78 °C, has been synthesized. The synthesis involved electrochemical oxidation of Hg(l,4,8,ll-tetraazacyclotetradecane)(BF4)2 in propiononitrile solution.11 In contrast to most other metals mercury forms polycations, e.g. Hgf+, Hgf+ or Hg3+. 

Cyclam, or 1,4,8,11-tetraazacyclotetradecane, was first synthesised, inadvertently, by van Alphen in 1937 through the reaction of 1,3 bis (2 aminoethyl)-aminopropane with 1,3 dibromopropane. The first major studies of the ligand by Bosnich et al. used X-ray crystallography to elucidate different conformations of the metal complexes of the macrocycle.27 Their synthesis was similar to van Alphen s procedure, but did not involve a template method and as a result yields were unimpressive. They showed that five out of the possible ten different metal-complex conformers exist in the solid-state (Figure 3.51). 

Lang DR, Davies JA, Lopes LGF, et al. A controlled NO-releasing compound synthesis, molecular structure, spectroscopy, electrochemistry, and chemical reactivity of R,R,5 )5 -fra s-[RuCl(NO)(cyclam)]5+ (1,4,8,11-tetraazacyclotetradecane). Inorg Chem. 2000 39 2294. 

The first example shows the synthesis of a C-C-bridged bis-macrocycle (Figure 2) [7]. The preparation of 1 is a condensation of a polyamine with a malonic ester derivative, in analogy to the procedure developed by Tabushi et al [8]. The tetraamide 1 is so insoluble that it precipitates and can be obtained practically pure from the reaction mixture. Its reduction to the octaamine takes place if the reaction with is done in diglyme (bis-(2-methoxyethyl)ether), in which 1 is partially soluble. The product 2 is an ideal ditopic ligand,since it has all the typical properties of 1,4,8,11-tetraazacyclotetradecane (cyclam), i. e. the thermodynamic and kinetical stability of its complexes and the C-C linkage between the two macrocyclic subunits does not reduce the coordination tendency of the amine nitrogens. 

---