Bonding in Cyclobutabenzene Chromium Tricarbonyl Complexes Studied by ¹³C NMR

Evidence of π-Bond Localization from ¹J(¹³C,¹³C)

authored by

H. Butenschön, B. Gabor, R. Mynott, H. G. Wey

Abstract

The¹³C NMR parameters of several cyclobutabenzenes (1a-1e) and their corresponding complexes (cyclobutabenzene)M(CO)₃(M = Cr, Mo, W. 2–4) are presented and discussed. Two cyclobutabenzenes 1b and 1d and their chromium tricarbonyl complexes 2b and 2d have been examined in greater detail: the signal assignments have been confirmed by 2 D-IN ADEQUATE and the one bond coupling constants ¹J(¹³C¹³C) measured at natural abundance using 1 D-INADEQUATE. Although the results provide no insight into why the chromium complex of 1,2-dioxocyclobutabenzene (1e) is much more reactive at the keto groups than le itself, they do reveal a weak but not negligible alternation of the carbon s-character in the C-C bonds of the 6-membered rings both in the free cyclobutabenzenes and in the complexes, thus providing evidence for slight bond fixation (Mills-Nixon effect).

External Organisation(s)

Max-Planck-Institut für Kohlenforschung

Type

Article

Journal

Zeitschrift fur Naturforschung - Section B Journal of Chemical Sciences

Volume

50

Pages

483-487

No. of pages

5

ISSN

0932-0776

Publication date

04.1995

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

General Chemistry

Electronic version(s)

https://doi.org/10.1515/znb-1995-0405 (Access: Open)