Molecular rare earth metal alumosilicates

Abstract

The synthesis and stabilization of molecular four-coordinated lanthanide alumosilicates was achieved by the use of a highly encumbered alumosilicate ligand LAl(OH·thf)(μ-O)Si(OH)(OtBu)₂ (1, L = HC{C(Me)N(2,6-iPr₂C₆H₃)}₂). Reactions between 1 and tris-cyclopentadienyl lanthanides (LnCp₃; Ln = Ce, Nd, Sm, Gd, Tb, Dy, Y, Er) derived in the isolation of eight compounds (2–9) where the ligand is observed in three different bonding modes: adducts (2, 3), spirocyclic (4) or cyclic (5–9) coordination compounds. The observed reactivity can be related to the ionic radius of the lanthanide atom and the nature of the oxygen donor-atom from the hydroxide (Al–OH) or hydroxyl (Si–OH) moieties in 1. Compounds 2–9 present general O–Al–O–Si–O–Ln connectivities with different degrees of substitution over the –OH groups in 1 and structural features with only slight variations over the alumosilicate moiety (O–Al–O–Si–O) upon the lanthanide coordination. The spirocyclic samarium derivative presents two tetra-coordinated samarium atoms with a tetrahedral and distorted square planar geometries, respectively, as a result of a highly strained polycyclic architecture.