Silylsubstituenten an phosphinomethanidliganden: dimere Al-Heterocyclen und molekülstruktur von {Me₂Al[C(PMe₂)(SiMe₃)₂]}₂

Six membered heterocycles {Me₂Al[CX(PMe₂)(SiMe₃)]}₂ (1: X = H, 2: X = SiMe₃) are obtained from Me₂AlCl and the appropriate solvent-free lithium phosphinomethanide. On the basis of NMR measurements, an equilibrium of both bis-equatorial X-substituted chair- and twist-conformations is assigned for 1 as well as {Me₂Al[CH(PMe₂)₂]}₂ (3). Only one isomer is present for 2 in solution. Single crystal X-ray structure determination of 2 shows a twist conformation in the solid state.