Synthesis, Crystal Structure, and Spectroscopic Characterization of a Series of Cubane-like Mo−Sb Clusters Containing a [Mo<sub>3</sub>SbOS<sub>3</sub>]<sup>7+</sup> Core

By using [Mo<sub>3</sub>OS<sub>3</sub>(μ-OAc)(dtp)<sub>3</sub>(py)] and [Mo<sub>3</sub>OS<sub>3</sub>(μ-OAc)<sub>2</sub>(dtp)<sub>2</sub>(py)] as the starting materials, a series of Mo−Sb clusters containing a [Mo<sub>3</sub>SbOS<sub>3</sub>]<sup>7+</sup> core, i.e., [Mo<sub>3</sub>(SbCl<sub>3</sub>)OS<sub>3</sub>(μ-OAc)(dtp)<sub>3</sub>(py)] (<b>1</b>), [Mo<sub>3</sub>(SbBr<sub>3</sub>)OS<sub>3</sub>(μ-OAc)(dtp)<sub>3</sub>(py)][(CH<sub>3</sub>)<sub>2</sub>CO] (<b>2</b>), [Mo<sub>3</sub>(SbI<sub>3</sub>)OS<sub>3</sub>(μ-OAc)(dtp)<sub>3</sub>(py)][(CH<sub>3</sub>)<sub>2</sub>CO] (<b>3</b>), and [Mo<sub>3</sub>(SbBr<sub>3</sub>)OS<sub>3</sub>(μ-OAc)<sub>2</sub>(dtp)<sub>2</sub>(py)][0.5(C<sub>2</sub>H<sub>5</sub>OH)] (<b>5</b>), have been obtained for the first time (OAc = OOCCH<sub>3</sub><sup>-</sup>, dtp = S<sub>2</sub>P(OC<sub>2</sub>H<sub>5</sub>)<sub>2</sub><sup>-</sup>, py = C<sub>5</sub>H<sub>5</sub>N). Among them, the cluster type of [Mo<sub>3</sub>(SbX<sub>3</sub>)OS<sub>3</sub>(μ-OAc)<sub>2</sub>(dtp)<sub>2</sub>(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 <sup>95</sup>Mo NMR spectra that the addition of SbX<sub>3</sub> 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 <sup>95</sup>Mo NMR spectra indicate an “inverse halogen dependence”. Crystal data:  <b>1</b>, triclinic, <i>P</i>-1, <i>a</i> = 11.746(4) Å, <i>b</i> = 12.462(3) Å, <i>c</i> = 17.851(6) Å, α = 73.54(2)°, β = 75.06(3)°, γ = 88.11(3)°, <i>V</i> = 2419(3) Å<sup>3</sup>, <i>Z</i> = 2, 4253 reflections, <i>R</i> = 0.055; <b>2</b>, triclinic, <i>P</i>-1, <i>a</i> = 12.76(1) Å, <i>b</i> = 17.86(1) Å, <i>c</i> = 11.882(4) Å, α = 75.05(4)°, β = 88.15(7)°, γ = 73.24(4)°, <i>V</i> = 2502(6) Å<sup>3</sup>, <i>Z</i> = 2, 1849 reflections, <i>R</i> = 0.086; <b>3</b>, triclinic, <i>P</i>-1, <i>a</i> = 11.727(4) Å, <i>b</i> = 12.951(3) Å, <i>c</i> = 17.957(4) Å, α = 73.52(3)°, β = 76.22(3)°, γ = 89.00(2)°, <i>V</i> = 2536(3) Å<sup>3</sup>, <i>Z</i> = 2, 6306 reflections, <i>R</i> = 0.053; <b>5</b>, triclinic, <i>P</i>-1, <i>a</i> = 13.261(4) Å, <i>b</i> = 13.529(4) Å, <i>c</i> = 12.535(8) Å, α = 101.54(3)°, β = 105.13(4)°, γ = 93.20(2)°, <i>V</i> = 2113(2) Å<sup>3</sup>, <i>Z</i> = 2, 4104 reflections, <i>R</i> = 0.060.