Tris(trimethylsilyl)siloxides of gadolinium and lanthanum: synthesis, structure and some properties

A series of gadolinium and lanthanum siloxide complexes of empirical formul a [(Me3Si)(3)SiO](3)Ln(L-n) {Ln = Gd, L-n = (THF)(2) (1), (MeCN)(2) (2), [N (C2H4)(3)N](2) (3), (4,4'-dipyridyl)(2) (4), (4,4'-dipyridyl)(1) (5); Ln = La, L-n = (THF)(4) (6)) have been prepared by the reaction of [(Me3Si)(2)N] (3)Ln (Ln = Gd, La) with (Me3Si)(3)SiOH or LnCl(3) (Ln = Gd) with (Me3Si)(3 )SiONa in various solvents. Both [(Me3Si)(3)SiO](3)Gd(THF)(2) (1) and [(Me3 Si)(3)SiO](3)Gd[N(C2H4)(3)N](2) (3) have been characterized by X-ray crysta llography. The Gd in both 1 and 3 has a trigonal-bipyramidal environment wi th three O atoms in equatorial and two B atoms (B = O in 1 and N in 3) in a xial positions. The symmetries of molecules of 1 and 3 are C-3i and C-3h, r espectively. The Gd-O-Si angles and the Gd-O distances are 161.2(3)degrees, 2.142(7) Angstrom in 1 and 165.4(2)degrees, 2.161(4) Angstrom in 3. The Gd -O(THF) distances in 1 are 2.448(9), 2.314(18) and the Gd-N distance in 3 i s 2.520(6) Angstrom. Gadolinium complex (1) and the lanthanum complex (6) r eadily absorb one and three moles of CO2, respectively to form the correspo nding carbonates. Compounds 1 and 6 sublime at 205 degrees C in vacuo to fo rm homoleptic siloxides. A subsequent rise in temperature results in their decomposition to give polylanthanosiloxanes, and (Me3Si)(3)SiOH as the only volatile product up to 300 degrees C. (C) 1999 Elsevier Science S.A. All r ights reserved.