Siloxane-linked tungsten complexes form a flexible metal–organic framework: 1-D channel structure and gas adsorption property

Abstract

Siloxane-linked tungsten complexes were synthesised by reacting a spiro-siloxane with tungsten(methyl) complexes, and they feature covalent W–Si/WSi bonds coordinated by pyridine derivatives. Among these, [Cp*(OC)₂(Ph)WSi(dmap)]₂(spiro) (4) (dmap = 4-dimethylaminopyridine, spiro = spiro-siloxane) formed a porous framework with a 1-D channel structure in the crystalline state through CH–π interactions, as evaluated by single-crystal X-ray diffraction (SC-XRD) analysis. Powder X-ray diffraction (PXRD) analysis revealed that the structure of 4 reversibly changes upon the release and uptake of solvent molecules. Notably, the micro-ED measurement of the desolvated framework demonstrated a change in the space group and up to 14% contraction of its b axis, supporting the transformation of its geometrical features. Furthermore, gas adsorption measurements revealed that this framework exhibited gate-opening behavior toward gaseous molecules (5 and 4 mol mol⁻¹ for CH₄ and O₂, respectively), highlighting the flexibility of the framework.