Dirhenium(III) complexes with N, N-dimethyladenine and 7-azaindole

Abstract

Re 2X 2(CH 3CO 2) 4 (X=Cl, Br) reacts with anionic N6,N6-dimethyladenine (dmad −) in ethanol to form dark purple Re 2X 2(dmad) 4, in which the acetate ligands are replaced by the N3/N9-bridging purine. Different relative orientations of the dissymmetric ligands about the ReRe axis lead to four stereoisomers producing resolved signals in the 1H NMR spectra. The compound can be reversibly protonated at N7 to yield the [ReX 2(Hdmad) 4] 4+. ion. Hdmad and (Bu 4N) 2[Re 2Cl 8] in ethanol form a red-brown dinuclear material formulated as [Re 2Cl 4(Hdmad) 2]- Cl·4H 2O·0.5C 2H 5OH, where the purine is N3/N9-bridging and N7-protonated. Heating (Bu 4N) 2[Re 2Cl 8] and 7- azaindole (Haza) without solvent leads to a brown Re 2Cl 2(aza) 4 material, in which different orientations of the N1/N7-bridging ligand again produce various stereoisomers. Magnetic anisotropy of the quadruple metal-metal bond probably contributes to the very large downfield shifts observed for the 13C signals of the carbon atoms just above the ReRe vector.