A study on electronic interaction two systems connected with a C=C bond: Preparation, and of (E)-and(2)-8,8′-(Ethene-l,2-diyl)bis(5-terf-butyl[2.2]metacyclophane)

(E)-8,8′-(Ethene-1,2-diyl)bis(5-tert-butyl]2.2]metacyclophane) (2) was obtained from a McMurry reaction of 5-tert-butyl-8-formyl[2.2jmetacyclophane (1). Irradiation of 2 with a high-pressure mercury lamp gave the corresponding (Z) isomer 3. X-ray crystallographic analyses of 2 and 3 show a certain degree of twisting of the bond connecting the metacyclophane unit and the central n system due to steric crowding. UV spectra of 2 and 3 and of the charge-transfer complexes [2/TCNE] and [3/TCNE] allow for a discussion of n-n interaction between the centrai stilbene subunit and the outer benzene rings of the metacyclophane units. Bis[2.2]metacyclophanes 2 and 3 reacted regioselectively with hexacarbonylchromiurn on the outer benzene rings giving 1:1 and 1:2 complexes 9-14 with tricarbonylchromium. No 1:3 and 1:4 complexes formed due to steric restrictions. Analysis of UV spectral data of the complexed [2.2]metacyclophanes was performed for an indication of π-π interactions in the complexes.