The reactions of cadmium halides with the 15-membered macrocyclic crow
n ethers, 15-crown-5 and benzo-15-crown-5, have been carried out and s
ix new complexes have been isolated and structurally characterized. Me
tal to ligand stoichiometries of 1:1, 2:1, 3:1 and 3:2 have been obser
ved with a variety of different formulations. Examples of charge separ
ated ion pairs ([(NH4)(benzo-15-crown-5)(2)](2)[Cd2I6]), halogen bridg
ed monomers, dimers or polymers ,[Cd(15-crown-5)(mu-Br)(2)CdBr(mu-Br)]
(2)(isolated from the same reaction mixture) and [(CdCl2)(2)CdCl2(15-c
rown-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 complexe
s. In-cavity coordination resulting in pentagonal bipyramidal geometri
es 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) d
isplays out-of-cavity coordination with one etheric donor distorted in
to an axial position of a distorted pentagonal bipyramid. The third co
ordination mode is secondary sphere coordination via hydrogen bonding
which is observed for [Cd(OH2)(2)(15-crown-5)][CdI3(OH2)](2) . 2(15-cr
own-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 com
plexes of 18-crown-6 (Cd-O=2.69(1)-2.81(1)Angstrom).