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

Abstract

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.

Nickel complexes incorporating an amido phosphine chelate with a pendant amine arm: Synthesis, structure, and catalytic Kumada coupling

“…Notably, one of the ipso carbons at P(2)-bound phenyl groups is weakly coordinated to Li(2) (C(23)-Li(2) = 2.500(5) A ˚). This phenomenon is unprecedented in lithium phosphine chemistry though similar close contacts are known for lithium aniline or lithium anilide complexes such as [Li(OEt 2 )] 2 [Zr(NMe 2 ) 2 (2,4-di-tertbutyl-6-(tert-butylamido)phenolate) 2 ] (2.406 A ˚), 36 Li 2 [CpCH(tertbutyl)N(p-anisyl)] (2.570(4) A ˚), 37 and {[(Me 3 Si) 2 CH](C 6 H 4 -2-NMe 2 )P}Li(THF) 2 (2.733(6) A ˚), 38 etc. In addition, the two lithium atoms are evidently bridged by the amido donor N(3) though the N(3)-Li(2) distance of 1.967(5) A ˚is significantly shorter than N(3)-Li(1) of 2.166(5) A ˚.…”