FORMATION OF RING-EXPANDED PRODUCTS FROM CERTAIN COMBINATIONS OF TETRAPHENYLDISILOXANEDIOLATES [(PH(2)SIOM')(2)O] (M'=LI OR NA) AND GROUP-4METAL CHLORIDES MCL(4)

Experimental conditions and combinations of reagents have been varied in reactions between [(Ph(2)SiOM')(2)O] (M' = Li or Na) and Group 4 me tal halides MCl(4), with the broad aim of assessing their affects on t he formation of ring-expanded products; Lithium-7 NMR spectroscopy was used to monitor the reaction between: [(Ph(2)SiOLi)(2)O] and MgCl2 . 2thf in thf (tetrahydrofuran) which gives a ring-expanded product. The reaction between [(Ph(2)SiONa)(2)O], prepared in situ from sodium met al and (Ph(2)SiOH)(2)O, and TiCl4 in a 3:1 molar ratio gave the sodium -bridged compound [Ti{O(SiPh(2)O)(2)}(3){Na(py)}(2)]. py, py = pyridin e, the first example of a six-membered titanasiloxane ring. Further re action with LiI gave the lithium-bridged analogue. The analogous react ion with HfCl4 gave the ring-expanded compound [Hf{Ph(2)Si(OSiPh(2)O)( 2)}(2)(py)(2)]. 2C(6)H(5)Me, the first examples of eight-membered hafn asiloxane rings. Results of Li-7, Si-29, and Na-23 NMR, IR, and single -crystal X-ray diffraction studies are reported.