Synthesis, Crystal Structure, and Spectroscopic Characterization of a Series of Cubane-like Mo−Sb Clusters Containing a [Mo3SbOS3]7+ Core

By using [Mo3OS3(μ-OAc)(dtp)3(py)] and [Mo3OS3(μ-OAc)2(dtp)2(py)] as the starting materials, a series of Mo−Sb clusters containing a [Mo3SbOS3]7+ core, i.e., [Mo3(SbCl3)OS3(μ-OAc)(dtp)3(py)] (1), [Mo3(SbBr3)OS3(μ-OAc)(dtp)3(py)][(CH3)2CO] (2), [Mo3(SbI3)OS3(μ-OAc)(dtp)3(py)][(CH3)2CO] (3), and [Mo3(SbBr3)OS3(μ-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 [Mo3(SbX3)OS3(μ-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 IR, Raman, UV−vis, and 95Mo 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 95Mo NMR spectra indicate an “inverse halogen dependence”. Crystal data:  1, triclinic, P-1, a = 11.746(4) Å, b = 12.462(3) Å, c = 17.851(6) Å, α = 73.54(2)°, β = 75.06(3)°, γ = 88.11(3)°, V = 2419(3) Å3, Z = 2, 4253 reflections, R = 0.055; 2, triclinic, P-1, a = 12.76(1) Å, b = 17.86(1) Å, c = 11.882(4) Å, α = 75.05(4)°, β = 88.15(7)°, γ = 73.24(4)°, V = 2502(6) Å3, Z = 2, 1849 reflections, R = 0.086; 3, triclinic, P-1, a = 11.727(4) Å, b = 12.951(3) Å, c = 17.957(4) Å, α = 73.52(3)°, β = 76.22(3)°, γ = 89.00(2)°, V = 2536(3) Å3, Z = 2, 6306 reflections, R = 0.053; 5, triclinic, P-1, a = 13.261(4) Å, b = 13.529(4) Å, c = 12.535(8) Å, α = 101.54(3)°, β = 105.13(4)°, γ = 93.20(2)°, V = 2113(2) Å3, Z = 2, 4104 reflections, R = 0.060.