A functional model for lanthanide doped silicate materials: synthesis of an apically substituted samarium silsesquioxane complex

Abstract

Steric protection of a trisilanol silsesquioxane (also referred to as a silasesquioxane) by one TBDMS group (SiMe₂Bu^t) generated a new siloxanolate ligand, (c-C₅H₉)₇Si₇O₉(OH)₂(OTBDMS) 1, that allows only restricted access to a co-ordinated metal. Lithiation afforded the stable complex (c-C₅H₉)₇Si₇O₉(OLi)₂(OTBDMS), which has allowed the generation of a samarium adduct [Sm(OC₆H₃Bu^t ₂-2,6){(c-C₅H₉)₇Si₇O₉(O)(OLi)(OTBDMS)}₂]. A structural study of this samarium adduct revealed two unusual features: an absence of stabilising M–O interactions with the siloxane core, and retention of one apical aryloxide group at the trivalent metal, through which the chemistry of a silica-functionalised Ln³⁺ ion might be modelled. X-Ray crystallography also revealed the dimeric hydrogen bonded structure of the disilanol ligands. The disilanol ligand 1 may also readily be converted into a dithallium salt, providing a potential precursor for further f-element derivatives of this disilanolate moiety.