Synthesis of alkaline earth metal bis(2-phosphaethynolates)

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)(3)Ca(O-CdropP)(2) shows bent Ca-O-C moieties and rather long Cdropp triple bonds of 1.575 A. 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(SiMe3)(2)](2) to (MeO)(2)CO gave a tridentate ligand which bridges two strontium atoms. The molecular structure of dimeric (dme)(2)Sr{OC[PC(O)OMe](2)) (5) showed the delocalization of the anionic charge within the O-C-P-C-P-C-O fragment.(C) 2002 Elsevier Science B.V. All rights reserved.