Synthesis and structure of sterically overloaded tetra-coordinated yttrium and lanthanum disiloxides

The synthesis, structures and reactivity of the spirocyclic yttrium and lanthanum disiloxides {[(CH2R2SiO)2]2M}H [M = Ln, Y; R = SiMe(SiMe3)2] 3 and 4 are reported. Compounds 3 and 4 were prepared from reactions of two equivalents of [CH2(R)2SiOH]2 [R = Si(SiMe3)2Me] (1) with one equivalent of M[N(SiMe3)2]2 (M = Y, La), respectively.