The coordination chemistry of the C1-symmetric bis(silyl)methyl ligand [CH(SiMe3){SiMe(OMe)2}]- revisited: Li/M- (M = Zn, Tl, Ce), Li4- or Ce2-methoxy-bridged alkyls

The following crystalline oligonuclear metal alkyls have been synthesised under mild conditions and structurally characterised: (THF)Li(mu-A)(mu-Cl)(mu3-OMe)Zn]2, Li(mu-A)2Tl]2(4 and 4'), Li4(mu-A)3(micro3-OMe)]5, (mu-A)Li2(mu-A)2(mu3-OMe)Ce(A)](6) and Ce(A)(mu2-OMe){mu2-OS(O)(CF3)O}]2(11)= CH(SiMe3){SiMe(OMe)2}]. Compounds 2-6 were obtained from Li(mu-A)]infinity(1) and ZnCl2(3), TlCl (4 and 4' and 5) and CeCl3(6), and 11 was isolated from K(A)(prepared from 1 + KOBu(t)) and cerium(III) triflate Ce(OTf)3. The principal novel features are (i) and (ii) as follows. As for (i), the diversity of ligand-to-metal bonding is noteworthy, the ligand being (a)C,O-bridging in 3{as in the known compounds 1 and in Li2Mg5(mu3-OMe)6(mu2-OMe)2(mu2-A)4](2)}; (b)C,O,O'-bridging and O,O'-chelating in 4 and 4'; (c)C,O,O'-bridging in 5; (d)C,O,O'-bridging and C,O-chelating in 6; and (e)C,O-chelating in 11. Regarding (ii), it is interesting that the ligand A]- is surprisingly ready to undergo fragmentation by Si-OMe cleavage and thereby present bridging methoxy ligands (mu2-OMe)2 to a pair of Ce3+ ions in 11, or mu3-OMe acting as a cap for triangular arrays of three hard metal ions (Mg3 in 2, LiZn2 in 3, Li3 in 5, and Li2Ce in 6).