Synthesis, crystal structure, and spectroscopic characterization of a series of cubane-like Mo-Sb clusters containing a [Mo3SbOS3]7+ core

By using [Mo3OS3(mu-OAc)(dtp)(3)(py)] and [Mo3OS3(mu-OAc)(2)(dtp)(2)(py)] as the starting materials, a series of Mo-Sb clusters containing a [Mo3SbOS3](7+) core, i.e., [Mo-3(SbCl3)(mu-OAc)(dtp)(3)(py)] (1), [Mo-3(SbBr3)OS3(mu-OAc)(dtp)(3)(py)][(CH3)(2)CO] (2), [Mo-3(SbI3)OS3(mu-oAC)(dtp)(3)(py)][(CH3)(2)CO] (3), and [Mo-3(SbBr3)OS3(mu-OAc)(2)(dtp)(2)(py)][0.5(C2H5OH)] (5), have been obtained for the first time (OAc = OOCCH3-, dtp = S2P(OC2H5)(2)(-), py = C5H5N). Among them, the cluster type of [Mo-3(SbX3)OS3(mu-OAc)(2)(dtp)(2)(py)] (X = Cl, Br, I) is an unprecedented species. It is shown from the results of the crystal structure analysis and LR, Raman, W-vis, and Mo-95 NMR spectra that the addition of SbX3 may cause an enhancement of Mo-Mo bonds and exerts a significant influence on the electronic structure. As the halogen atoms are softer in Cl, Br, I order. The energies of the electron transfer gradually decrease leading to a red shift of UV-vis peaks. The Mo-95 NMR spectra indicate an "inverse halogen dependence". Crystal data: 1, triclinic, P-1, a = 11.746(4) Angstrom, b = 12.462(3) Angstrom, 17.851(6) Angstrom, alpha = 73.54(2)degrees, beta = 75.06(3)degrees, gamma = 88.11(3)degrees, V = 2419(3) Angstrom(3), Z = 2, 4253 reflections, R = 0.055; 2, triclinic, P-1, a = 12.76(1) Angstrom, b = 17.86(1) Angstrom, c = 11.882(4) Angstrom, alpha = 75.05(4)degrees, beta = 88.15(7)degrees, gamma = 73.24(4)degrees, V = 2502(6) Angstrom(3), Z = 2, 1849 reflections, R = 0.086; 3, triclinic, P-1, a = 11.727(4) Angstrom, b = 12.951(3) Angstrom, c = 17.957(3) (C) Angstrom, alpha = 73.52(3)degrees, beta = 76.22(3)degrees, gamma = 89.00(2)degrees, V = 2536(3) Angstrom(3), Z = 2, 6306 reflections, R = 0.053; 5, triclinic, P-1, a = 13.261(4) Angstrom, b = 13.529(4) Angstrom, c = 12.535(8) Angstrom, alpha = 101.54(3)degrees, beta = 105.13(4)degrees, gamma = 93.20(2)degrees, V = 2113(2) Angstrom(3), Z = 2, 4104 reflections, R = 0.060.