The use of (arene)chromium complexes to control the stereochemistry of [2.2]orthocyclophane

The conformations of mono- and bis(tricarbonylchromium) complexes of 1,2;5,6-dibenzocycloocta-1,5-diene (1) have been investigated. The 1H NMR data of free ligand 1 and those of the three complexed compounds 2–4 have been compared and discussed relative to the X-ray structures. Despite compound 1 has been found to exist as a mixture of boat and chair conformations in solution, the 1H NMR spectra of 2 and 3 in DMSO-d6 show only the syn configuration (boat conformation) at room temperature. The trans bis(tricarbonylchromium) complex 3 exists in a chair conformation. q 2004 Elsevier B.V. All rights reserved.