Steric and Solvation Effects on the Aggregation of Lithium Thioamidates: Single-Strand Polymers with (LiS)(n)() and (LiNCS)(n)() Backbones.
The addition of methyllithium or n-butyllithium to alkyl isothiocyanates produces lithium thioamidates {Li[RCS(NR')]}(n)(). Three such compounds were structurally characterized after recrystallization from THF. When R = n-Bu and R' = t-Bu, an unsolvated hexamer {Li[n-BuCS(N-t-Bu)]}(6) (1) is obtained. By contrast, the solvated derivatives {Li.THF[MeCS(N-t-Bu)]}(infinity) (2.THF) and {Li.2THF[MeCS(NMe)]}(infinity) (3.2THF) form single-strand polymers. The monosolvated complex 2.THF involves four-membered rings with an (LiS)(n)() backbone whereas the disolvate 3.2THF is comprised of LiNCS repeating units. The structures of all three aggregates can be generated via sterically directed solvation of a common dimeric precursor. Crystal data for 2.THF: C(10)H(20)NLiOS, monoclinic, P2(1)/a (#14), a = 9.129(2) Å, b = 11.099(2) Å, c = 12.537(2) Å, beta = 94.14(2) degrees, V = 1267.0(4) Å(3), Z = 4. Crystal data for 3.2THF: C(11)H(22)NLiSO(2), monoclinic, P2(1)/a (#14), a = 10.974(3) Å, b = 8.575(5) Å, c = 14.898(5) Å, beta = 91.33(3) degrees, V = 1401.6(10) Å(3), Z = 4.
Chivers
Tristram
T
Department of Chemistry, University of Calgary, 2500 University Drive N.W., Calgary, Alberta, Canada T2N 1N4.
Downard
Andrew
A
Parvez
Masood
M