Characterization and electrochemical properties for rhenium(III) ion incorporated into linear-type S-bridged trinuclear complexes. Crystal structures of Delta Lambda- and Delta Delta/Lambda Lambda-[Re{Ir(aet)(3)}(2)](3+) (aet=2-aminoethanethiolate)

摘要

The meso (1a) isomer of the (IrReIrIII)-Re-III-Ir-III trinuclear complex [Re{Ir(aet)(3)}(2)](3+) (aet = 2-aminoethanethiolate) was newly prepared by SnCl2.2H(2)O reduction of an acidic mixture offac(S)-[Ir(aet)(3)] and NH4ReO4, and purified by column chromatography. The racemic (1b) isomer was isolated by the reaction offac(S)-[Ir(aet)(3)] with.[Re(Metu)(6)]Cl-3 (Metu = N-methylthiourea). The crystal structures of 1aBr(3) and 1bBr(3).H2O were determined by X-ray crystallography. Both isomers consist of two terminal fac (S)-[Ir(aet)(3)] units and a central Re atom, forming the linear-type S-bridged trinuclear structure. The central Re atom is situated in an octahedral environment with (ReS6)-S-III chromophore. Both 1a and 1b are fairly stable in water under aerobic condition and they were characterized spectrochemically. Further, 1b was optically resolved by a column chromatographic method, and it is characterized by CD spectroscopy. The Re-III ion, which has a d(4)-electronic configuration, in 1b indicates a lower magnetic moment (1.11mu(B)) at room temperature, reflecting well the paramagnetic shifts for H-1 and C-13 NMR signals. Each cyclic voltammogram of [Re{M(act)(3)}(2)](3+) (M = Ir-III, Rh-III) shows a reversible redox process (M-IV/III) in a positive region and they are confirmed by a spectroelectrochemical technique. Their redox potentials at E-0' = +0.34- +0.60 V (vs. Ag/AgCl) are lower than those for the corresponding complexes, whereas it was elucidated that the oxidation state of the Re-III ion is highly stabilized in the S-bridged trinuclear structures. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 41]