A sulfur-bridged sandwich cubane-type molybdenum-antimony cluster [(H(2)O)(9)Mo(3)S(4)SbS(4)Mo(3)(H(2)O)(9)](8+) (2) has been synthesized through the reaction of incomplete cubane-type molybdenum cluster [Mo(3)S(4)(H(2)O)(9)](4+) (1) with antimony metal, and has been isolated as 2(pts)(8).24H(2)O (2.pts) (Hpts = p-toluenesulfonic acid), whose structure has been characterized by X-ray crystallography. Crystal data of 2.pts: triclinic, space group P&onemacr;, a = 14.468(3) Å, b = 18.531(5) Å, c = 13.713(6) Å, alpha = 105.26(2) degrees, beta = 119.71(1) degrees, gamma = 72.48(3) degrees, V = 3016(1) Å(3), Z = 1, D(calcd) = 1.696 g cm(-)(3), D(obsd) = 1.72 g cm(-)(3), R (R(w)) = 4.7 (7.5) for 6593 reflections (I > 2.0sigma(I)). The Mo-Sb distances (3.68[2]) Å) are much longer than the Mo-Mo (2.717[7] Å) distances. Peak positions and epsilon values (lambda(max), nm (epsilon, M(-)(1) cm(-)(1))) of the electronic spectrum of 2.pts in 2 M HCl are 384 (13 220), 625 (10 440), and 700 (10 080). The (121)Sb Mössbauer parameters (delta = -2.64 mm s(-)(1), e(2)qQ = 18.1 mm s(-)(1), eta = 0.29), and the binding energies (eV) and full widths at half-maximum (in parentheses, eV) obtained from XPS spectrum (Sb(3d3/2), 540.3(2.3); Mo(3d3/2), 233.2(2.1); Mo(3d5/2), 230.2(1.9); (C(1s) = 285.0)) of 2.pts indicate that the oxidation number of antimony is III, and the mean oxidation number of molybdenum is +3.5.