Fixation of CO(2) by Zinc(II) Chelates in Alcoholic Medium. X-ray Structures of {[Zn(cyclen)](3)(&mgr;(3)-CO(3))}(ClO(4))(4) and [Zn(cyclen)EtOH](ClO(4))(2).
The fixation of CO(2) on Zn(II) chelates in alcoholic medium was studied in efforts to synthesize alkyl carbonates. In the presence of a base, such as NEt(3), the tetraazacyclododecane complex of Zn(II) in alcoholic solution binds CO(2) and forms a &mgr;(3)-carbonate complex. This complex was characterized by NMR spectroscopy and X-ray analysis. Crystal data: orthorhombic; space group Pcba; a = b = c = 21.850(5) Å; alpha = beta = gamma = 90 degrees; V = 10431.7(6) Å(3); Z = 8. The central Zn atom is coordinated to the four nitrogen donor atoms and to one oxygen of the bridging carbonate group. In an organic solvent such as DMSO, the complex exists in equilibrium with the decarboxylated Zn(II) complex. In addition, a Zn(II)(cyclen)(ethanol) complex was isolated and characterized by X-ray analysis. Crystal data: monoclinic; space group P2(1)/n; a = 12.707(5), b = 11.780(5), c = 15.642(5) Å; alpha = gamma = 90 degrees; beta = 105.250(5) degrees; V = 2259.0 (6) Å(3); Z = 4. The central Zn atom is coordinated to four nitrogen donor atoms and the oxygen of ethanol. We were not successful in converting this complex to the ethyl carbonate complex. The results of this study are discussed in reference to those published in the literature.
Schrodt
Antje
A
Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstrasse 1, 91058 Erlangen, Germany.
Neubrand
Anton
A
van Eldik
Rudi
R