A Neutral Heteroleptic Molybdenum Cluster trans-[{Mo6I8}(py)2I4]

Abstract

Despite that the chemistry of octahedral cluster complexes has been actively developed recently, there are still a lot of unexplored areas. For example, to date, only a few halide M6-clusters with N-heterocycles are known. Here, we obtained an apically heteroleptic octahedral iodide molybdenum cluster complex with pyridine ligands—trans-[{Mo6I8}(py)2I4] by the direct substitution of iodide apical ligands of [{Mo6I8}I6]2– in a pyridine solution. The compound co-crystalized with a monosubstituted form [{Mo6I8}(py)I5]– in the ratio of 1:4, and thus, can be described by the formula (pyH)0.2[{Mo6I8}(py)1.8I4.2]·1.8py. The composition was studied using XRPD, elemental analyses, and 1H-NMR and IR spectroscopies. According to the absorption and luminescence data, the partial substitution of apical ligands weakly affects optical properties.

The Remarkably Robust, Photoactive Tungsten Iodide Cluster [W6I12(NCC6H5)2]

“…Related molybdenum cluster compounds have shown lower stabilities [25] . For example (pyridineH) 0.2 [Mo 6 I 8 (pyridine) 1.8 I 4.2 ] was reported to show a gradual mass loss starting above 100 °C until 350 °C followed by a strong mass loss at 400 °C, corresponding to the formation of [Mo 6 I 12 ] [10b] …”

“…However, it is assumed that [Mo 6 Cl 12 (CH 3 CN) 2 ] is an intermediate in the production of the oxygen sensor made from [Mo 6 Cl 12 ] [9] . Recently, luminescence properties of the neutral molybdenum cluster species (PyridineH) 0.2 [Mo 6 I 8 (pyridine) 1.8 I 4.2 ] were reported to show negligible photoluminescence in the solid‐state [10b] …”

“…However, investigations regarding the luminescence of neutral and cationic cluster species are scarce, even though first examples were reported decades ago [14] . To the best of our knowledge, only a few compounds have known crystal structures and have been characterized in regard to their photophysical properties [5,10b,15] …”

Preparation, photoluminescence and excited state properties of the homoleptic cluster cation [(W6I8)(CH3CN)6]4+

“…In general, the aforementioned investigations of the photophysical properties of tungsten and molybdenum halide clusters have been carried out on anionic species ([M 6 X 8 L 6 ] 2− ). While neutral and cationic clusters are reported to exist with various different solvents as ligands, 16 only a few crystal structures 17 are reported, and for only three compounds, namely [M 6 I 8 (DMSO) 6 ](NO 3 ) 4 (M = Mo, W) and [Mo 6 I 8 (pyridine) 2 ]I 4 have the luminescence properties been studied. 17 b , d Therefore, our aim was to synthesize new cationic tungsten halide clusters and characterize their photoluminescence properties.…”