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 pr oduces lithium thioamidates {Li[RCS-(NR')]}(n). Three such compounds were s tructurally characterized after recrystallization from THF. When R = n-Bu a nd 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 po lymers. The monosolvated complex 2.THF involves four-membered LiNCS rings w ith an (LiS)(n) backbone whereas the disolvate 3.2THF is comprised of LiNCS repeating units. The structures of all three aggregates can be generated v ia sterically directed solvation of a common dimeric precursor. Crystal dat a for 2.THF: C-10-H20NLiOS, monoclinic, P2(1)/a (#14), a = 9.129(2) Angstro m, b = 11.099(2) Angstrom, c = 12.537(2) Angstrom, beta = 94.14(2)degrees, V= 1267.0(4) Angstrom(3), Z = 4. Crystal data for 3.2THF: C11H22NLiS2, mono clinic, P2(1)/a (#14), a = 10.974(3) Angstrom\, b = 8.575(5) Angstrom, c = 14.898(5) Angstrom, beta = 91.33(3)degrees, V= 1401.6(10) Angstrom(3), Z = 4.