title: Coulomb repulsion versus cycloaddition: formation of anionic four-membered rings from sodium phosphaethynolate, Na(OCP).
abstract: Carbon dioxide and two equivalents of Na(OCP) form, in an equilibrium reaction, a CO2 adduct of the composition Na2(P2C3O4). The anion of this salt, [O2C-P(CO)2P](2-), is built up by a four-membered 1,3-diphosphetane-2,4-dione ring and a carboxylate unit attached to one of the phosphorus atoms. A remarkable π-delocalization was observed within the OCPCO moiety. The stepwise reaction mechanism leading to Na2(P2C3O4) was investigated with quantum chemical calculations. Accompanied by the release of CO2, Na2(P2C3O4) reacts with both 2-iodopropane and 4,4',4''-trimethoxytriphenylmethyl chloride to form four-membered cyclic anions. For comparison the analogous reactions were performed with Na(OCP) instead of Na2(P2C3O4) and the results are discussed in detail.
authors.affiliation: Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland. hgruetzmacher@ethz.ch benkoe@inorg.chem.ethz.ch.
authors.forename: Dominikus
authors.initials: D
authors.lastname: Heift
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Benkő
authors.forename: Hansjörg
authors.initials: H
authors.lastname: Grützmacher