Soluble {[Rh 2(μ-OOCCH 3) 2(dbbpy) 2][BF 4]} n molecular wire and [Rh 2(μ-OOCCH 3) 2(dbbpy) 2L 2] 2+ complexes; dbbpy = 4,4′-di- tert-butyl-2,2′-bipyridine: Synthesis and physicochemical characterization

Abstract

Binuclear Rh(II) compounds [Rh 2(μ-OOCCH 3) 2(dbbpy) 2(H 2O) 2](CH 3COO) 2 ( 1) (dbbpy = 4,4′-di- tert-butyl-2,2′-bipyridine), [Rh 2(μ-OOCCH 3) 2(dbbpy) 2(H 2O) 2](BF 4) 2·H 2O·CH 3CN ( 2), [Rh 2(CH 3COO) 2(C 18H 24N 2) 2(CH 3CN) 2](BF 4) 2·4CH 3CN ( 3) and {[Rh 2(μ-OOCCH 3) 2(dbbpy) 2][BF 4]} n ( 4) have been synthesized and characterized with spectroscopic methods. Structure of complex 3 has been determined using X-ray crystallography. Rhodium atoms in compound 3 have distorted octahedral coordination with O and N atoms in equatorial positions and Rh atom and CH 3CN molecule in axial coordination sites. Reduction of rhodium(II) compounds with aqueous 2-propanol leads to the formation of polymetallic compound {[Rh 2(μ-OOCCH 3) 2(dbbpy) 2][BF 4]} n ( 4) containing [Rh 2] 3+ core. Compound 4 shows strong antiferromagnetic properties, μ = 0.18–1.73 M.B. in the range 1.8–300 K, J = −597 cm −1. Electrochemistry of compounds 3 and 4 in CH 3CN has been investigated. Compound 4 exhibits a poorly reversible oxidation system at E 1/2 = −0.92 V (Δ E p = 0.19 V) and in solution in DMF is slowly oxidized to 3 even in total absence of oxygen. Complex 3 is irreversibly oxidized to Rh(III) compound at E pa = 1.48 V and irreversibly reduced at E pc = −1.02 V to lead to the unstable polynuclear complex 4 in CH 3CN.