A NEW SYNTHETIC PATHWAY FOR TRIS-MU-DISULFIDO-MU-3-THIO-TRIANGULO-TRIMOLYBDENUM(IV) COMPLEXES - PREPARATION, CHARACTERIZATION AND STRUCTURE OF [MO3S(S2)3(OOC-CHS-CH2-COOH)3]2-

A new synthetic pathway for complexes containing the polynuclear core [Mo3S7]4+ is described: [Mo3S7(S2)3]2- reacts with HBr to [Mo3S7Br6]2- which seems to be a useful intermediate for further ligand substitution. A new complex with mercapto- succinic acid C4H6O4S (H3msa) as ligand could be prepared. 1H NMR and 13C NMR spectra and X-ray crystal structure analysis are in agreement with the bidentate coordination of mercapto-succinic acid, where S- and COO- are bound to the same molybdenum atom forming a five-membered ring. A monoclinic crystal, space group C2, of the composition [C18H30N3]2[Mo3S7(Hmsa)3][Mo3S7(Hmsa)2(msa)] Br·6H2O was used for X-ray diffraction. The cell parameters are a=21.968(7), b=13.423(13), c= 18.828(3) Å, β=94.23°, Z=2, Dc=1.606 g/cm3, μ(Mo Kα)=13.51 cm-1. [Mo3S7(Hmsa)3]2- is stable in water and air, and it can be precipitated from aqueous solution by the addition of large three-fold charged cations. It can be deprotonated reversibly to [Mo3S7(msa)3]5- in water. The pK values are 3.95, 4.41, 5.02 (1 M KCl, 25 °C). To confirm the above described procedure as a useful approach for [Mo3S7]4+ complexes, a similar compound with 2-mercapto-benzoic acid was also prepared. © 1990.