An unprecedented nanocage-like and heterometallic [MoIV3O₄]-polyoxomolybdate hybrid

Abstract

The solvothermal oxidation of [MoO(OCCH)(HO)]·ZnCl has been established as a general route toward [MoO]-incorporated polyoxomolybdates (Mo-POMs). Two unprecedented family members: the first Mo-Mo-Mo nanocage cluster, Na[MoMoMoO(OH)Py]·11HO (1) and the first heterometallic hybrid, [MoMoZn(PO)(OH)Opy]·2(CHN)·3(CHN)·2HO (2) have been prepared and characterized by X-ray crystallography, elemental and DFT theoretical analyses, XPS, mass spectroscopy, cyclic voltammetry, and IR spectroscopy.

Metal–metal bonds in polyoxometalate chemistry

“…74 Some of the follow-up studies involve reports on [Sb III 3Mo IV 3Mo VI 15O55(OH)2(py)3] − , 111 [Mo@Mo IV 6Mo V 6Mo VI 9O54(OH)4(py)6] 4− , 112 and [Na@Mo IV 12Mo V 4Mo VI 3O43(OH)(py)12] (all in Figure 6). 113 These polyanions have peculiarities in terms of structure, and they have been in a great detail outlined in the primary literature.…”

“…From these results, the rearrangements of the metal−metal bonds in the super-reduced Keggin 106 appear plausible (vide supra). With the addition of different heterogroups (e.g., PO4 3− and GeO4 3− ) the group of Xu also discovered the formation of [Mo IV 3Mo VI 10Zn(PO4)4(OH)2O31py3] 2− , 113 and [Mo IV 6Mo VI 10Ge3O48py6], 112 which can be described as lacunary POMs incorporating triangular moieties.…”

“…The original motivation in Xu's work was the development of hydrogenation catalysts based on frustrated Lewis pair systems that involve highly reduced POMs with partial clusterlike and partial metal-oxo features. 112,113,116 In this line, the γisomer of [Mo IV 6Mo VI 7O32(OH)4(C5H5N)6] 2− is a representative system that has shown an exceptional heterogeneous catalytic conversion of nitrobenzene to aniline with a yield of over 99% under mild conditions (Figure 7.b). 116 The Xu group has elaborated that in the presence of protic solvents and hydrazine, the pyridine ligands of the Mo IV site are replaced, and the POM is then activated.…”

Selective Oxidative Coupling of Amines Using Mesoporous MoOx Catalysts

“… BEs of Mo 3d from the literature have also been compared to assign the real oxidation state of the present measurement (Table S4). − The meso -MoO x -300 material is a mixture of +4, +5, and +6 oxidation states of molybdenum, with a majority of +6 oxidation states, as shown in Figure A. XPS data for synthesized molybdenum oxide show three doublet pairs (i.e., six synthetic peaks) and fit well to all the experimental Mo 3d spectra.…”

Extended Mo3IV-Polyoxometalates: 1D-[Mo6IVMo4VIGe2ZnO31py9 (H2O)]4– and 2D-[Mo3IVMo9VIZn6P7O56py8]+ (py = Pyridine)

“…Electron-rich polyoxometalates (POMs) featuring metal–metal bonding have been receiving increasing attention due to their unusual molecular/crystal/electronic structures and promising applications in sustainable batteries, supercapacitors, nanoelectronics (POMtronics), medicine, and catalysis. , Deeply reduced M 3 IV -POMs (M = Mo, − W − ) are of special interest in aspects of the peculiarities in polytropic molecular/crystal/electronic structures, − the next generation of molecular cluster batteries, , electronic storage, − memristive devices, and Lewis field catalysis − among others. The Mo VI → Mo IV super-reduction of POMs dramatically changes the molecular and electronic structures and hence physicochemical properties in the following ways: (1) the rigid peripheral Mo V/VI  O double bonds are replaced by labile Mo IV ←: L dative bonds (L = Lewis base ligand), which functionalizes POMs with Mo IV Lewis acid active sites; (2) the d 2 -Mo IV addenda atom forms strong triangular Mo–Mo bonds with the two neighboring Mo IV atoms in the resulting Mo 3 IV triad boasting six d 2 –d 2 bonding electrons; (3) the coordinating ability of the internal capping oxygen atom in the incomplete cuboidal [M 3 IV (μ 3 -O 4 )­(μ 2 -O 3 )] unit is markedly weakened by the enhanced μ 3 -O–Mo 3 IV bonding; (4) the Mo IV Lewis acidity and Lewis basicity of the bridging (O b ) or thermal (O t ) oxygen atoms are enhanced by Mo 3 IV → O x M IV y electron transfer; and (5) the much shorter Mo IV –Mo IV bonds than the Mo VI ···Mo VI separations by more than 0.6 Å lead to the contraction and lowered symmetry of POMs .…”