Synthesis,characterization and reactivity of linear-type s-bridged trinuclear complexes containing vanadium(III) ion. Crystal structures of [V~(III){M(aet)_3}_2](ClO_4)_3 (M = Rh~(III), Ir~(III); aet = 2-aminoethanethiolate)

摘要

Reactions of fac(S)-[M(aet)_3] (M = Rh~(III), Ir~(III); aet = 2-aminoethanethiolate) with an excess of VCl_3 gave linear-type S-bridged trinuclear complexes [V~III]{M(aet)_3}_2]~(3+) (M = Rh~(III) 1, Ir(III) 2). The #DELTA##DELTA# isomers (1a(ClO_4)_3 and 2a(ClO_4)_3) were selectively crystallized and their structures were determined by X-ray diffraction. Both the complex cations consist of two terminal fac(S)-[M(aet)_3] units and a central vanadium atom, which is situated in an octahedral environment with a V~(III)S_6 chromophore. The Ir complex 2a was also formed by using V~(IV)OCl_2 instead of V~(III)Cl_3 in a redox reaction, whereas the Rh complex 1a was not formed by a similar method. The optically active isomer (#LAMBDA##LAMBDA#-1b) of the Rh complex was selectively obtained by using #LAMBDA#-fac(S)-[Rh(aet)_3], and characterized by IR, UV-VIS absorption and CD spectra. All the obtained complexes exhibit a unique strong absorption band at ca. 18 X 10~3 cm~(-1). Stability and reactivity relating to V-S bond cleavage for the complexes were investigated using UV-VIS absorption spectroscopic methods. These studies show first order decomposition or metal exchange. While 2a has weaker V-S bonds than 1a (from the X-ray analyses), the former is considerably more stable in water than the latter. Cyclic voltammograms of 1a and 2a in water show only irreversible oxidation and reduction waves including V~(IV/III) and V~(III/II) processes. The V(III) ions in the S-bridged trinuclear structures exhibit a lower magnetic moment (2.59 #mu#_B for 1a and 2.27 #mu#_B for 2a) at room temperautre than the spin-only value for a d~2 electronic configuration.