Abstract
The first iodide cluster of molybdenum with the metal cage in the form of a tetragonal pyramid (Bu4N)[Mo5OI13]·THF (I) and cocrystallizate (Bu4N){[Mo5OI13]0.9[Mo6I14]·THF (II) are synthesized for the first time by heating a LiI–I2–Mo mixture in a temperature range of 300–400°С followed by the extraction of the product. Complexes I and II are studied by X-ray diffraction analysis (CIF files CCDC nos. 2063029 (I) and 2063030 (II)). The molybdenum atoms in [Mo5OI13]– form a square pyramid with Mo–Mo distances of 2.67 Å between the basal molybdenum atoms and the Mo–Mo distances equal to 2.72 Å between the apical and basal molybdenum atoms. The oxygen atom is coordinated to the pyramid base (Mo–μ4-O 2.10 Å). The cluster anion [Mo5OI13]– can be presented as the octahedral cluster anion [Mo6I14]2– in which the position of the {MoI}– fragment (d0, 6e) is occupied by the isoelectronic oxygen atom (s2p4, 6e). In the structure of compound II, the [Mo5OI13]– and [Mo6I14]2– cluster anions occupy close atomic positions.
Highlights
The formation of stable cluster groups with metal– metal bonds of various multiplicity is a characteristic feature of lower molybdenum and tungsten halides [1]
The pentanuclear clusters with the square pyramid structure are of interest as possible precursors of heterometallic octahedral clusters of the {M5M'X8}4+ type (M' is heteroatom), especially in the case of X = I, since these are the iodide cluster complexes of molybdenum [Mo6I8L6]z (L are terminal ligands, and z is the charge of the coordination sphere) that demonstrate the highest quantum yields and lifetimes [3]
A mixture of Mo, I, and LiI was heated at 400°С for 48 h in the ratio assuming the formation of the cluster salt of the pyramidal Li2Mo5I13 cluster, which is presumably formed by analogy to the known [W5I13]2– salts [6]
Summary
The formation of stable cluster groups with metal– metal bonds of various multiplicity is a characteristic feature of lower molybdenum and tungsten halides [1]. The first example of the molybdenum iodide cluster (Bu4N)[Mo5OI13]·THF with the metal cage structure as a square pyramid was obtained and studied by X-ray diffraction analysis (XRD) in this work. A mixture of the Mo powder (1.403 g, 0.014 mol), I2 (4 g, 0.016 mol), and LiI (0.767 g, 0.0057 mol) in a dry box was placed in a glass ampule, which was evacuated, sealed, and placed in a muffle furnace, which was heated to 400°С for 4 h This temperature was maintained for 48 h. The single crystals of the cocrystallizate (Bu4N){[Mo5OI13]0.9[Mo6I14]0.1}·THF (II) were obtained by the saturation of a mixture of the clusters in THF with hexane vapors.
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