SYNTHESIS AND CRYSTAL-STRUCTURES OF ALKALI-METAL (-NEOMENTHYLCYCLOPENTADIENYL COMPLEXES())

Polymeric alkali-metal (+)-neomenthylcyclopentadienyl complexes [M(eta (5)-C5H4R)](infinity) (M = Li 1a, Na 2a or K 3a) and [M(eta(5)-C5H4R)L ](infinity) [M = Na, L = tetrahydrofuran (thf) 2b; M = K, L = thf 3b, L = 1, 2-dimethoxyethane (dme) 3c] and monomeric neomenthylcyclopentad ienyl(N, N, N', N'-tetramethylethane-1, 2-diamine)lithium 1b have been synthesized and characterised by single-crystal X-ray analyses. Compo unds 1a, 2a, 2b and 3c have multidecker polymeric chain structures wit h average M-Cp (centroid) (M = Li, Na or K) distances of 2.010 Angstro m (Li), 2.437 and 2.503 Angstrom (Na), and 2.874 Angstrom (K). The ave rage Cp-R-M-Cp-R angles are 166.9 (Li), 170.2 and 135.1 (Na), and 135. 5 degrees (K), respectively. The (+)-neomenthyl groups on successive c yclopentadienyl rings are oriented along the polymeric zigzag chain wi th approximate twist angles of 116.2 (1a), 91.1 (2a), 179.9 (2b) and 1 65-8 degrees (3c) respectively. In the monomeric half-sandwich compoun d 1b the lithium atom is bonded to the pentahapto cyclopentadienyl rin g at a metal-to-centre distance of 1.910 Angstrom.