The coordination chemistry of the C1-symmetric bis(silyl)methylligand [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(l-A)(l-Cl)(l3-OMe)Zn]2 (3), [Li(l-A)2Tl]2 (4 and 4), [Li4(l-A)3(l3-OMe)] (5),
[(l-A)Li2(l-A)2(l3-OMe)Ce(A)] (6) and [Ce(A)(l2-OMe){l2-OS(O)(CF3)O}]2 (11) [A = CH(SiMe3){SiMe(OMe)2}].
Compounds 2–6 were obtained from [Li(l-A)]∞ (1) and ZnCl2 (3), TlCl (4 and 4 and 5) and CeCl3 (6), and 11 was
isolated from K(A) (prepared from 1 + KOBut) 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(l3-OMe)6(l2-OMe)2(l2-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 (l2-OMe)2 to a pair of Ce3+ ions in 11, or l3-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).
D a l t o n T r a n s . , 2 0 0 5 , 2 9 8 8 – 2 9 9 3