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Trends in ortho-carboranes 1-X-2-R-1,2-C2B10H10 (R = Ph, Me) bearing an exo-CN-bonded substituent group (X = NO, N=NR ' or NHR '')

Lookup NU author(s): Emeritus Professor Bill Clegg, Dr Mark Elsegood


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The preparation and crystal structures of four ortho-carboranyl-nitrogen compounds, PhCb degrees N=N(C6H4Me-4) (1), PhCb degrees NHNH(C6H4Me-4) (2), MeCb degrees NHNHPh (3) and PhCb degrees NHOH (4) (Cb degrees = 1,2-C2B10H10; nitrogen groups at cage carbon C1, Ph or Me at C2), the last as a 1,4-dioxane solvate, are reported. Comparisons of their structures with those of other ortho-carboranyl-nitrogen systems studied earlier reveal further correlations between their cage C-C and exo-C-N bond distances and bond orders. Substituent orientations and bond distances (cage C1-C2, exo-C1-N) in RCb degrees NHR '' systems (R = Ph or Me at C2) are consistent with dative pi-bonding from a nitrogen lone pair into the cage carbon p-AO otherwise responsible for cage C1-C2 sigma-bonding. Their C1-C2 bond distances are remarkably sensitive to the planar (sp(2)) or pyramidal (sp(3)) nature of the NHR '' group. The N=O and N=NR' residues in RCb degrees X prefer to be orientated in plane with the cage C1-C2 in contrast to the RCb degrees NHR '' systems. Correlations between their cage C-C and exo-C-N bond distances and the B-11 NMR chemical shifts of their antipodal boron atoms reflect the pi-bonding characteristics of the nitrogen substituent. (C) 2009 Elsevier Ltd. All rights reserved.

Publication metadata

Author(s): Fox MA, Peace RJ, Clegg W, Elsegood MRJ, Wade K

Publication type: Article

Publication status: Published

Journal: Polyhedron

Year: 2009

Volume: 28

Issue: 12

Pages: 2359-2370

ISSN (print): 0277-5387

ISSN (electronic): 1873-3719

Publisher: Pergamon


DOI: 10.1016/j.poly.2009.04.041


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