The synthesis of alkali metal magnesiates MMg(NON TCHP )(HMDS) (M = K, Rb or Cs; HMDS = bis(trimethylsilyl)amide; NON TCHP = 4,5-bis(2,4,6-tricyclohexylanilido)-2,7-diethyl-9,9-dimethyl-xanthene) via coordination of Mg(NON TCHP ) with M(HMDS) is reported. Each complex is characterised using single crystal X-ray diffraction measurements and NMR spectroscopic methods. In the solid-state, each system exists as a 1D-polymer that assembles via bridging M‧‧‧π(arene) interactions to two Mg(NON TCHP )(HMDS) − units. For KMg(NON TCHP )(HMDS), polymerization occurs via coordination of each K-center to TCHP and xanthene arene rings. In contrast, for the heavier group 1 magnesiates, RbMg(NON TCHP )(HMDS) and CsMg(NON TCHP )(HMDS), the alkali metals exhibit alternating xanthene, xanthene- and TCHP, TCHP-coordination along the polymer chain. This work highlights the influence that group 1 metal cations can have on the long-range structure of bis(anilido)xanthene magnesiate complexes. • A series of heavier alkali metal salts of a xanthene bridged diamido/bis(trimethylsilyl)amido magnesium anion. • Polymeric structures of prepared complexes vary depending on the alkali metal cation (K, Cs or Rb) involved. • Alkali metal···arene interactions in the complexes are alkali metal specific.
Evans et al. (Wed,) studied this question.