Syntheses and Some Properties of S-Bridged Pentanuclear Co(III)–Hg(II) or Rh(III)–Hg(II) Complexes with 2-Aminoethanethiolate. Crystal Structures of [{Rh(aet)3}2(HgCl2)3] and [{Rh(aet)3}2Hg3(NO3)4](NO3)2

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Abstract
S-Bridged pentanuclear complexes [{Rh(aet)3}2(HgCl2)3] (1) and [{M(aet)3}2Hg3(NO3)4]2+ (M = Rh(III), 2 and Co(III), 3) were newly prepared by the reaction of fac(S)-[M(aet)3] with HgCl2 or Hg(NO3)2; where aet denotes 2-aminoethanethiolate. The crystal structures of 1 and 2 were determined by X-ray diffraction methods. These complexes consist of two fac(S)-[M(aet)3] subunits, three Hg atoms, six chlorides (for 1) or nitrates (for 2), and water molecules, in which the configuration of the five metals is an approximately regular trigonal-bipyramid. Each Hg atom in these complexes takes a highly distorted tetrahedral geometry. There are three kinds of nitrates in [{Rh(aet)3}2Hg3(NO3)4](NO3)2, bridged bidentate, monodentate, and anion. Both 1 and 2 possess a novel chirality due to the helical structures of three Rh–S–Hg–S–Rh chains. Although 1 was insoluble in water, 2 and 3 were optically resolved by fractional precipitation. These complexes were characterized by their absorption, CD, and NMR spectra. The coordinated nitrates in 2 and 3 were readily replaced by water molecules when dissolved in water. The stabilities of the S-bridged pentanuclear complexes are also discussed.

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