Synthesis of alkaline earth metal bis(2-phosphaethynolates)

• Published in: Journal of organometallic chemistry Vol. 643; pp. 189 - 193
• Main Authors: Westerhausen, Matthias, Schneiderbauer, Stefan, Piotrowski, Holger, Suter, Max, Nöth, Heinrich
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2002
• Subjects: Alkaline earth metal bis(2-phosphaethynolates); Delocalization; Phosphaalkynes; Triple bonds; Alkaline earth metal bis(2-phosphaethynolates); Triple bonds; Delocalization; Phosphaalkynes
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(01)01267-0

The reaction of dimethylcarbonate with magnesium bis(triisopropylsilyl phosphanide) or the alkaline earth metal bis[bis(trimethylsilyl)phosphanide] in 1,2-dimethoxyethane yields the corresponding bis(2-phosphaethynolate) of magnesium ( 1), calcium ( 2), strontium ( 3) and barium ( 4). These compounds decompose upon isolation and have to be stored in an etheral solution at low temperatures. The structure of (dme) 3Ca(OCP) 2 shows bent CaOC moieties and rather long CP triple bonds of 1.575 Å. In order to ensure a quantitative reaction an excess of dimethylcarbonate has to be used. For the strontium derivative a side reaction of a 1:3 stoichiometry of M[P(SiMe 3) 2] 2 to (MeO) 2CO gave a tridentate ligand which bridges two strontium atoms. The molecular structure of dimeric (dme) 2Sr{OC[PC(O)OMe] 2} ( 5) showed the delocalization of the anionic charge within the OCPCPCO fragment. The reaction of alkaline earth metal bis[bis(trimethylsilyl)phosphanides] with dimethylcarbonate yields quantitatively the corresponding phosphaethynolates of calcium, strontium and barium. A side reaction with another equivalent of dimethylcarbonate gives the new anion 2,6-bis(methoxy)-3,5-diphospha-1,7-dioxaheptatrienide-4-olate as shown in the pictogram.