CROWN ETHER MEDIATED CADMIUM HALIDE DIMERS AND POLYMERS

摘要

The reactions of cadmium halides with the 15-membered macrocyclic crown ethers, 15-crown-5 and benzo-15-crown-5, have been carried out and six new complexes have been isolated and structurally characterized. Metal to ligand stoichiometries of 1:1, 2:1, 3:1 and 3:2 have been observed with a variety of different formulations. Examples of charge separated ion pairs ([(NH4)(benzo-15-crown-5)(2)](2)[Cd2I6]), halogen bridged monomers, dimers or polymers ([Cd(15-crown-5)(OHMe)(mu-Br)CdBr3],[Cd(15-crown-5)(mu-Br)(2)CdBr(mu-Br)]( 2)(isolated from the same reaction mixture) and [(CdCl2)(2)CdCl2(15-crown-5)](n)), and hydrogen bonded finite chains or polymers ([Cd(OH2)(2)(15-crown-5)][CdI3(OH2)](2) . 2(15-crown-5). 2CH(3)CN and [CdI2(OH2)(2)(THF)]. benzo-15-crown-5) have been isolated. Three different types of 15-crown-5 coordination modes have been observed in these complexes. In-cavity coordination resulting in pentagonal bipyramidal geometries about Cd2+ was observed in [(CdCl2)(2)CdCl2(15-crown-5)](n), [Cd(15-crown-5)(OHMe)(mu-Br)CdBr3], and [Cd(OH2)2(15-crown-5)][CdI3(OH2)](2) . 2(15-crown-5). 2CH(3)CN. [Cd(15-crown-5)(mu-Br)(2)CdBr(mu-Br)](2) displays out-of-cavity coordination with one etheric donor distorted into an axial position of a distorted pentagonal bipyramid. The third coordination mode is secondary sphere coordination via hydrogen bonding which is observed for [Cd(OH2)(2)(15-crown-5)][CdI3(OH2)](2) . 2(15-crown-5). 2CH(3)CN. The good fit of Cd2+ within the cavity of 15-crown-5 results in shorter bonding contacts and a more narrow distribution in Cd-O values (2.273(7)-2.344(6)A) than observed for cadmium halide complexes of 18-crown-6 (Cd-O=2.69(1)-2.81(1)Angstrom). [References: 31]