Formation of ring-expanded products from certain combinations of tetraphenyldisiloxanediolates [(Ph2SiOM′)2O](M′= Li or Na) and group 4 metal chlorides MCl4

Abstract

Experimental conditions and combinations of reagents have been varied in reactions between [(Ph₂SiOM′)₂O](M′= Li or Na) and Group 4 metal halides MCl₄, with the broad aim of assessing their affects on the formation of ring-expanded products. Lithium-7 NMR spectroscopy was used to monitor the reaction between [(Ph₂SiOLi)₂O] and MgCl₂·2thf in thf (tetrahydrofuran) which gives a ring-expanded product. The reaction between [(Ph₂SiONa)₂O], prepared in situ from sodium metal and (Ph₂SiOH)₂O, and TiCl₄ in a 3 : 1 molar ratio gave the sodium-bridged compound [Ti{O(SiPh₂O)₂}₃{Na(py)}₂]·py, py = pyridine, the first example of a six-membered titanasiloxane ring. Further reaction with LiI gave the lithium-bridged analogue. The analogous reaction with HfCl₄ gave the ring-expanded compound [Hf{Ph₂Si(OSiPh₂O)₂}₂(py)₂]·2C₆H₅Me, the first examples of eight-membered hafnasiloxane rings. Results of ⁷Li, ²⁹Si, and ²³Na NMR, IR, and single-crystal X-ray diffraction studies are reported.