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4278865 
Journal Article 
Direct measurement of the diamagnetic anisotropy of the ferrocenyl moiety: The origin of unusual H-1 NMR shifts in ferrocenyl-triptycenes and barrelenes 
Mcglinchey, MJ; Nikitin, K 
2014 
Yes 
Journal of Organometallic Chemistry
ISSN: 0022-328X
EISSN: 1872-8561 
751 
809-814 
WOS:000329864700084 
The H-1 NMR chemical shifts of 12 ferrocenyl-triptycenes and -barrelenes, in conjunction with their X-ray crystallographically-determined structures, provide a picture of the diamagnetic anisotropic effect of the ferrocenyl moiety. It reveals that protons sited directly above a cyclopentadienyl ring are incrementally shielded by approximately 1.2 ppm, whereas those positioned adjacent to the iron atom are deshielded by approximately 1.5 ppm. These data allow an NMR-derived evaluation of the chi value for ferrocene as of -1660 x 10(-36) m(3)/molecule, about 25% higher than the currently accepted value for benzene. A particular feature of the present approach is that data are provided for individual protons in clearly defined geometric positions rather than for rotating methyl groups. (C) 2013 Elsevier B.V. All rights reserved. 
Ferrocene; NMR chemical shifts; Aromaticity; Ring current; Magnetic anisotropy