STRUCTURE OF THE DOUBLE SALT [CO-II(CL)L(3)]CL-[CO-III(CO3)L3]CL[L(3),5,8,11-TETRAETHYL-1,4,7,10-TETRAAZACYCLODODECANE) AND RELATED SPECIES

The hydrochloride of the chiral cyclen ligand L(3) ,5,8,11-tetraethyl- 1,4,7,10-tetraazacyclododecane] reacted with Na-3[Co-III(CO3)(3)] in a cidic and alcoholic aqueous solution to give two crystalline complexes , [Co-II(Cl)L(3)]Cl-[Co-III(CO2)L(3)]Cl and [Co-II(Cl)L(3)]Cl-2 the cr ystal structures of which have been determined. The former contains an equimolar mixture of two markedly different crystallographically inde pendent molecules in the unit cell, which have been crystallised indep endently as two salts variously hydrated. These differ from one anothe r in the oxidation state of the metal, the co-ordination number, and t he configurations of asymmetric nitrogens. The molecule [Co-II(CI)L(3) ]Cl is distorted square pyramidal with the Cl- ion at the apex and RRR R configurations of the four asymmetric N atoms; the carbonate cobalt( III) complex is six-co-ordinated and the N atoms have RSRS configurati ons. The corresponding mixed-valence compound with bromide did not sep arate, although the analogue of the monomeric carbonate was isolated. The structure determinations of the carbonate and [Co-II(CI)L(3)]Cl sh ow that the molecular geometries are essentially the same as those fou nd in the double salt. The formation and stabilisation of the cobalt(I I) species is probably due to the steric requirements of the macrocycl e.