Disiloxanediolate complexes

Quite in contrast to the alkoxides and simple silox-ides, related disiloxanediolate complexes of cerium(rv) form spontaneously upon treatment of cerium(III) precursors with... 

Sc(acac)3] crystallizes in the orthorhombic space group Pbca (Andersen et al., 1973). The stmcture consists of discrete Sc(acac)3 molecules. The scandium(III) ion is six-coordinate, and the coordination polyhedron can be described as a slightly distorted octahedron (fig. 7). The site symmetry is close to D3. Another example of a six-coordinate scandium(III) )3-diketonate complex is [Sc(dbm)3] (Zaitseva et al., 1990). Two different crystal structures are described, one with a triclinic and one with a monochnic cell. So far, no scandium(lll) )3-diketonates with coordination number higher than six have been described. Because of the small ion size of Sc +, coordination number six is the general rule fortius rare-earth ion. Also in the trinuclear scandium(III) disiloxanediolate complex [(Ph2Si0)20]2Sc3(acac)5], the coordination number of Sc + is six as well (Lorenz et al., 2001) (fig. 8). 

Fig. 8. Molecular structure of the trinuclear scandium(ni) disiloxanediolate complex [(Ph2Si0)20]2Sc3(acac)5]. The atomic coordinates are taken from Lorenz et al. (2001). No hydrogen atoms are shown.

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