Metal containing new inorganic ring systems based on siloxane and phosphazane frameworks

Abstract

High-field ³¹P NMR spectroscopy and single crystal X-ray diffraction studies have been used to study the ring opening and nucleophilic substitution reactions of the Λ ³-cyclotriphosphazane [EtNPCl]3. The synthesis of the ring opened silicophosphonate [RSi(OH){OP(O)(H)(OH)}]₂O (R = (2,6-iPr₂C₆H₃)NSiMe₃) (1) represents the first ever molecular silicophosphonate to be isolated bearing free reactive hydroxyl groups. The structure and conformation of the bulky aryloxide substituted Λ ³-cyclotriphosphazane derivative [EtNP(OAr)]₃ (Ar = 2,6-iPr₂C₆H₃) (2) has also been investigated. Interaction of 2 with transition metal precursor complexes leads to the isolation of phosphazane metal complexes with different mode of co-ordination of 2. Further, the reaction of Cp Ti(OAr)Cl2 (Ar = 2,6-(CH₃)₂C₆H₃OH) with O{SiPh₂(OH)}₂ gave the eight-membered trititanosiloxane [Cp Ti(Cl) (O(SiPh₂O)₂SiPh₂O) (3). Siloxane chain expansion effects, presumed to be a consequence of ring strain, have been observed in the product. The presence of reactive Ti-Cl bond in 3 offers opportunities for its reaction chemistry to be explored.