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

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.