Cationic derivatives of RhCl[P(η2-C7H7)3]. An intramolecular Diels–Alder rearrangement in the tripodal ligand tri(1-cyclohepta-2,4,6-trienyl)phosphane, P(C7H7)3

Starting from the chloro-rhodium(I) complex, RhCl[P(η2-C7H7)3] (1), several salts such as {Rh[P(η2-C7H7)3]}+X− (X−=BF4− (2), CF3COO− (5), CF3SO3− (7)) and {Rh(LL)[P(η2-C7H7)2(C7H7)]}+BF4− (LL=1,10-phenanthroline (4a) or 2,2ʹ-bipyridine (4b)) have been prepared. The reaction of 1 with trimethylsilyl trifluoromethane sulfonate, CF3SO2OSiMe3, has been found to involve a stereospecific 4:2 Diels–Alder cycloaddition between two coordinated cyclohepta-2,4,6-trienyl substituents to give a dinuclear rhodium(III) complex, {Rh2[P(η3-C14H15)(C7H7)]2(μ-Cl)3}+(CF3SO3−) (8), which has been characterized by NMR spectroscopy and an X-ray structure analysis.