Remarkable Dichotomy of Oligomeric Chain Structures of Dilithium(amidoalkyl-cyclopentadienide) Systems Li2[C5H4-CHR-NAr]

The dilithium compounds Li2[Cp-CHR1-NAr1] 2A (R1 = tert-butyl, Ar1 = p-anisyl) and Li2[Cp-CHR2-NAr2] 2B (R2 = methyl, Ar2 = o-anisyl) were synthesized by means of fulvene routes as previously described. Single crystals were obtained from THF/pentane. Both systems feature oligomeric chain structures in the solid state. Compound 2A exhibits a head-to-tail arrangement of monomeric units with recurring chain-constructing (amide)N-Li-(η5-Cp) units whereas 2B favors a head-to-head type structure with alternating η5-Cp-Li-η5-Cp lithiocene and bis(N,O-chelate)Li building blocks. In each case the remaining Li+ ions are coordinated toward the periphery of the main chain as Li(THF)2 (2A) or Li(THF) (2B) solvates.