Lithium-7 nuclear magnetic resonance investigation of the structure of some aromatic ion pairs

13C and 23Na solid‐state NMR spectra of organosodium compounds

“…This finding may thus be compared with the shift difference of ca 3.5 ppm found in solution for 7 Li on going from cyclopentadienyllithium ( 8.37 ppm) 27 to lithiocene ( 11.05 ppm, both values relative to external aqueous 1 M LiCl) (H. Hausmann and H. Günther unpublished data). Compound 3 is also the only complex where a significant chemical shift anisotropy term has been found.…”

Syntheses and Properties of Tin‐Containing Conjugated Heterocycles

“…In the case of the cyclopentadiene derivative 15 , the bonds inside the ring are C1−C2 1.413, C2−C3 1.414, C3−C4 1.413, and C4−C5 1.413 Å. In addition, the analysis of the 7 Li NMR signal of 11 ( δ =−4.36 ppm in C 6 D 6 ) showed the high shielding effect of the diatropic ring current from the 6 π‐electron system and is comparable to the 7 Li NMR signal in 15 (−8.37 ppm in [D 8 ]THF) …”

“…In the case of the cyclopentadiene derivative 15,t he bonds inside the ring are C1À C2 1.413,C 2 ÀC3 1.414, C3ÀC4 1.413, and C4ÀC5 1.413 .Inaddition, the analysiso ft he 7 Li NMR signal of 11 (d = À4.36 ppm in C 6 D 6 )s howedt he high shielding effect of the diatropic ring current from the 6 p-electron system and is comparable to the 7 Li NMR signal in 15 (À8.37 ppm in [D 8 ]THF). [35] Comparing the 119 Sn NMR signal in CDCl 3 for 11 (d = 163.3 ppm) and for 14 (d = À88 ppm), dianion 11 [36] shows a much highera romatic character (compared with compound 7). [29b] Finally,aNICS value of À5.96 ppm, points to acertain aromaticc haracter of 11.…”

The Reaction of some Carbonyl and Thiocarbonyl Compounds with Prenyl‐ and Crotyllithium in Tetrahydrofuran Solution

“…Contact between anion and cation is probably preferred at the primary ends of the ally1 anions, because electron density is highest there, and simply for steric reasons (the peripheral solvation shell of the lithium cation probably contains three molecules of tetrahydrofuran), the lithium cation being located above the n-cloud [17] [HI. The assignment of cis-geometry to 2 is only based on the structures of the derived, unbranched adducts 32, 35 and 38 (see the Table) which of course does not provide strict proof, and on analogy with the geometries of several vinylogs in ammonia solution [19] 1201.…”