Here we report on the synthesis, structure, and characterization of the first example of a polyoxopalladate (POP)-based metal-organic framework (MOF). This novel class of materials comprises discrete polyoxo-13-palladate(II) nanocubes [Pd 13 O 8 (AsO 4 ) 8 H 6 ] 8− decorated by four Ba 2+ ions on each of two opposite faces. These secondary building units (SBUs) are linked to each other via rigid linear organic groups, resulting in a stable 3D POP-MOF framework, which exhibits interesting sorption as well as catalytic properties.
We report on the discovery of the first two examples of cationic palladium(II)-oxo clusters (POCs) containing f-metal ions, [Pd II 6 O 12 M 8 {(CH 3 ) 2 AsO 2 } 16 (H 2 O) 8 ] 4 + (M = Ce IV , Th IV ), and their physicochemical characterization in the solid state, in solution and in the gas phase. The molecular structure of the two novel POCs comprises an octahedral {Pd 6 O 12 } 12À core that is capped by eight M IV ions, resulting in a cationic, cubic assembly {Pd 6 O 12 M IV 8 } 20 + , which is coordinated by a total of 16 terminal dimethylarsinate and eight water ligands, resulting in the mixed Pd II -Ce IV /Th IV oxoclusters [Pd II 6 O 12 M 8 {(CH 3 ) 2 AsO 2 } 16 (H 2 O) 8 ] 4 + (M = Ce, Pd 6 Ce 8 ; Th, Pd 6 Th 8). We have also studied the formation of hostguest inclusion complexes of Pd 6 Ce 8 and Pd 6 Th 8 with anionic 4-sulfocalix[n]arenes (n = 4, 6, 8), resulting in the first examples of discrete, enthalpically-driven supramolecular assemblies between large metal-oxo clusters and calixarenebased macrocycles. The POCs were also found to be useful as pre-catalysts for electrocatalytic CO 2 -reduction and HCOOH-oxidation.
We report on the
synthesis and characterization of the first polyoxo-noble-metalate-containing
metal–organic framework (MOF) material, wherein the preformed
MIL-101 has been impregnated with the discrete, cuboid-shaped polyoxopalladate
[Pd13Se8O32]6– (Pd13Se8), leading to the composite Pd13Se8@MIL-101. This material was characterized by FTIR,
TGA, elemental analysis, powder-XRD, N2 sorption (BET),
SEM-EDX, and XPS. Furthermore, the Pd13Se8@MIL-101
composite was shown to be an effective, stable, and recyclable heterogeneous
precatalyst for the Suzuki−Miyaura cross-coupling reaction
at room temperature utilizing environmentally benign solvents, such
as water and methanol.
The class of peroxo-cerium-containing polyoxometalates has been discovered via the synthesis of the 9-peroxo-6c e r i u m ( I V ) -c o n t a i n i n g 3 0 -t u n g s t o -3 -g e r m a n a t e , [Ce IV 6 (O 2 ) 9 (GeW 10 O 37 ) 3 ] 24− (1). Polyanion 1 consists of a cyclic [Ce 6 (O 2 ) 9 ] 6+ assembly that is stabilized by three dilacunary [GeW 10 O 37 ] 10− Keggin fragments. The title polyanion 1 is solution-stable, on the basis of 183 W nuclear magnetic resonance, and was shown to act as a recyclable homogeneous catalyst for the selective, microwave-activated sulfoxidation of the model substrate methionine to the sulfoxide in the absence and to the sulfone in the presence of hydrogen peroxide. Solution and solid-state Raman as well as solid-state infrared studies of 1 demonstrated the complete loss (and regain) of the nine peroxo groups in situ during the catalytic cycle, suggesting that the peroxo-free {Ce 6 (GeW 10 ) 3 } skeleton remains most likely intact during the catalytic cycle. Solid-state X-ray photoelectron spectroscopy measurements showed that peroxo loss is accompanied by reduction of the cerium ions from +4 to +3, which is fully reversible. Density functional theory calculations are in complete agreement with all of these observations and furthermore suggest that the reduction of the six cerium(IV) ions is accompanied by the formation of molecular dioxygen.
A family of five host–guest assemblies comprising
different
metal ions inside a cuboid 12-palladium-oxo cage, [MO8Pd12L8]
n− (MPd
12
L
8
, M = ScIII, CoII, CuII, L
= AsO4
3–; M = CdII, HgII, L = PhAsO3
2–), was synthesized
and structurally characterized in the solid state by single-crystal
X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR),
and thermogravimetric analysis, and their solution and gas-phase stability
were validated by multinuclear NMR spectroscopy and electrospray-ionization
mass spectrometry (ESI-MS). The polyoxopalladates (POPs) ScPd
12
As
8
, CoPd
12
As
8
, and CuPd
12
As
8
represent the first three
examples of the MPd12As8 archetype. The unique
cubic ligand field of {MO8} allows for collecting the speciation
profiles of the POPs in solution using 45Sc and 113Cd NMR techniques. Detailed magnetic and electron paramagnetic resonance
(EPR) studies were performed on CuPd
12
As
8
. Catalytic studies
on MPd12As8 (M = CuII and CoII) supported on SBA-15 unveiled a guest metal-dependent structure–function
relationship, with CuPd
12
As
8
being the more efficient precatalyst
for the hydroconversion of o-xylene in a fixed-bed
reactor.
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