Synthesis, NMR spectroscopic characterization and structure of bis(1,2-dimethoxyethane-O,O')barium bis[1,3-bis(trimethylsilyl)-2-phenyl-1-aza-3-phosphapropenide]

Barium-bis[bis(trimethylsilyl)phosphanide] 1 reacts with two equivalents of benzonitrile to give barium bis[1,3-bis(trimethylsilyl)-2-phenyl-1-aza-3-phosphapropenide]; the choice of the solvent determines whether a tris(tetrahydrofuran)- or a bis(1,2-dimethoxyethane)-complex 2 can be isolated. 2 crystallizes from DME as red cuboids (monoclinic, C2/c, a = 1627.0(3), b = 1836.6(3), c = 1602.5(2) pm; beta = 96.071(12)degrees; V = 4761.7(12); Z = 4; wR(2) = 0.0851). The phosphorus atom displays a pyramidal surrounding in contrast to the planar coordination sphere of the nitrogen atom. In addition a twist within the P-C-N skeleton of the heteroallyl anion is observed.