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Oxygen/sulfur-bridged incomplete cubane-type molybdenum aqua cluster [Mo3XS3(H2O)9]4+ reacts with diethylenetriamine (dien) to give [Mo3XS3(dien)2(dien-)]Cl3.nH2O (A, X = O, n = 3; B, X = S, n = 4; dien- = NH2(CH2)2NH(CH2)2NH), each cluster having a deprotonated dien. The X-ray structure analysis of A revealed that a proton dissociated from an amino group of one of the three dien ligands as shown in Figure 1. The Mo2-N27 distance (1.987(4) angstrom) is clearly shorter than the other eight Mo-N distances (2.231(3) - 2.277(3) angstrom).The 13C NMR spectra (Figure 2) of the Mo-dien complexes, A and B, indicate that the carbon atoms are more shielded than those of cobalt-dien complexes so far reported. It seems reasonable to suppose that deprotonation of an amino group of the dien causes higher electronic density at carbon atoms of the dien ligands. Only two signals have been observed, and in the solution the deprotonation is not fixed at a specific dien, as compared to the X-ray analysis. The spacing of the two signals in both A and B, where all the dien ligands coordinate facially, is large (ca. 9 ppm), which coincides with the large spacing of the signals of facial Co-dien complexes (ca. 12 ppm). The corresponding Mo-dien complex with Mo3O4 core is under investigation.
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