M. Veith et al., HOMO AND HETERO METAL AMIDES OF TRIS-(TER T-BUTYLAMINO)METHYLSILANE -POLYCYCLES AND CLUSTERS WITH LI, NA, MG, AL AND TL, Chemische Berichte, 126(12), 1993, pp. 2625-2635
The hydrogen atoms attached to nitrogen in tris(tert-butylamino)methyl
silane (1) can be substituted by metallic maingroup elements in a quit
e general way. If 1 is treated with trimethylaluminium apart from the
monosubstituted product MeSi(tBuNH)(2)(tBuNA1Me(2)) (2) the trisamide
MeSi(tBuNAlMe(2))(3) (3) is obtained. In similar ways complete substit
ution of the amino hydrogen atoms in 1 yields the compounds MeSi[tBuNM
gN(SiMe(3))(2)](3) (6), [MeSi(tBuNLi)(3)](2) (10), and [MeSi(tBuNTl)(3
)](2) (11), the later two being dimeric. If methylmagnesium iodide is
allowed to react with 1 the intermediate MeSi(tBuNMgI)(3) (4) in some
instances can be isolated as the THF adduct or may react with a furthe
r equivalent of the Grignard compound to generate the complex [MgI(THF
)(5)]+ [MeSi(tBuNMgI)(3)CH3.THF](-) (5). The aluminium compound 2 has
been used to access to heterometallic amides combining aluminium and s
odium as in MeSi(tBuNA1-Me(2))(tBuNNa)(tBuNH) (7) or magnesium and alu
minium as in the dimeric compounds [MeSi(tBuNA1Me(2))(tBuNH)(tBuNMgI)]
(2) (8) and [MeSi(tBuNA1Me(2))(tBuNH)(tBuNMgMe)](2) (9). X-ray structu
re analyses reveal 3 (tricyclic SiN3Al3 skeleton with Al-N distances f
rom 2.014 to 2.025 Angstrom A), 6 (tricyclic SiN3Mg3 skeleton), and 7
[bicyclic SiN3AlNa skeleton with Na - N distances of 2.47(1) and 2.52(
1)Angstrom A] to be monomeric even in the solid state. The compopunds
8 and 9 (both pentacyclic with spiro magnesium atoms) form centrosymme
tric dimers by Mg-I-Mg and Mg-(CH3)-Mg bridges, respectively. The dime
rs 10 and 11 are completely different in terms of chemical bonding: wh
ile in the lithium compound 10 a centrosymmetric polycycle is formed b
y principly ionic interactions of the lithium atoms with corresponding
nitrogen atoms, the centrosymmetric dimer in 11 is held together by T
l-Tl bonds. The X-ray structure analysis of 5 reveals the anion contai
ning a Mg-coordinated CH3-.