Solvent-Controlled Polymerization of Molecular Strontium Vanadate

Article Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

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Solvent-Controlled Polymerization of Molecular Strontium Vanadate Monomers into 1D Strontium Vanadium Oxide Chains Benjamin Schwarz,† Maximilian Dürr,‡ Katharina Kastner,† Nora Heber,† Ivana Ivanovic-́ Burmazovic,́ *,‡ and Carsten Streb*,†,§ †

Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany Chair of Bioinorganic Chemistry, Friedrich-Alexander-University Erlangen-Nuernberg, Egerlandstr. 1, 91058 Erlangen, Germany § Helmholtz-Institute Ulm, Helmholtzstr. 11, 89081 Ulm, Germany Downloaded via NOTTINGHAM TRENT UNIV on August 15, 2019 at 20:29:43 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

‡

S Supporting Information *

ABSTRACT: We report the polymerization of a solvent-stabilized molecular strontium vanadium oxide monomer into infinite 1D chains. Supramolecular polymerization is triggered by controlled solvent-exchange, which leads to oligomer and polymer formation. Mechanistic insights into the chain formation were obtained by solid-state, solution, and gas-phase studies. The study shows how reactivity control of molecular metal oxides can be used to assemble complex inorganic polymeric structures.

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leading to a multitude of supramolecular aggregates.22−25 Based on these guiding design principles, we have recently started to explore the linkage of vanadium oxide clusters with large alkali or alkaline earth metals as potential models for industrial catalysts, e.g., those used in the oxidative dehydrogenation of alkanes.26−28 By the use of SrII or BaII cations, we gained access to a series of large supramolecular clusters29 and 1D strontium30 or barium vanadium oxide chains.31 In these studies, we noted that the bulkiness of the solvent ligands employed significantly affects the resulting supramolecular architectures.29−31 Further architectural control was achieved by using additional organic linkers such as urea.30 Here, we expand the use of bulky solvent ligands to enable the controlled, solvent-induced formation of 1D chains from single-source molecular precursors containing both the vanadium oxide cluster of choice and a suitable, solvent“protected” strontium linker. The conversion is triggered by reducing the steric bulk and increasing the exchange lability of the solvent employed, leading to an in situ deprotection of the monomer and subsequent chain assembly. Structural insights into the monomer and chain assemblies in solution and the solid state are presented together with a suggested “polymerization” mechanism. To date, the predictable bottom-up design of metalfunctionalized POMs has been mainly limited to tungstates

INTRODUCTION Polyoxometalates (POMs) are polynuclear metal oxide aggregates which can be considered as molecular analogues of classical solid-state metal oxides.1−3 POMs are highly sought after compounds for applications in homogeneous catalysis, molecular electronics, and medicine and nanomaterials design.3 Currently, the assembly of POMs into larger, often supramolecular, aggregates has opened new research areas ranging from fundamentals in complexity formation4,5 through to energy conversion and storage.6,7 The desire to assemble POMs into larger, supramolecular architectures has led to the development of a multitude of aggregation strategies8 where small linkers such as metal cations or organic ligands are employed to give complex nanostructures. Organic linkages connected covalently or noncovalently to the POM have been used to link the clusters into multidimensional grids or frameworks.9−12 Very recently, the formation of 1D POM chains linked via CLICK chemistry (1,3-dipolar cycloaddition between organic azides and alkynes) was reported,13 which expands the field of organic linking strategies even further. However, for deployment under harsh reaction conditions, purely inorganic linkages with high thermal and chemical stability are desirable.8 Pioneering work highlighted the assembly of multidimensional framework materials formed by linking mixed-valent polyoxovanadates with 3d transition metals14 or alkaline earth metals.15 Furthermore, POMs were linked via AgI-based bridging units which has led to several 1D chains and 2D grids.16−21 Later studies were focused on the linkage of POMs through transition metals or lanthanides, © XXXX American Chemical Society

Received: June 5, 2019

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DOI: 10.1021/acs.inorgchem.9b01665 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry and molybdates that feature vacant coordination sites (socalled lacunary species).1,32 Only recently, similar concepts have been developed for the metal functionalization of dodecanuclear polyoxovanadates of the type [(MLx)aV12O32Cl]n− (a = 0, 1, 2; M = metal cation; L = ligand, e.g., MeCN, Cl−, etc.)33−36 Metal functionalization starts with the molecular vanadium oxide (NMe2H2)2[V12O32Cl]3− (= {V12}) which features two metal binding sites occupied by weakly bound organic dimethylammonium (NMe2H2+) cations. Subsequent incorporation of 3d transition-metal cations resulted in the formation of the respective mono- and difunctionalized compounds.33−36

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EXPERIMENTAL SECTION

Synthesis of 1. (nBu4N)3[H3V10O28] (0.204 g, 0.12 mmol) and SrCl2·6 H2O (0.052 g, 0.20 mmol) were suspended in dimethyl sulfoxide (DMSO, 7 mL). The reaction mixture was heated to 110 °C for 5 h, whereby the color changed from yellow to brownish green. Diffusion crystallization with ethyl acetate resulted in the formation of yellow-green crystals. The product was washed with ethyl acetate and was air-dried. Yield: 0.08 g (0.04 mmol, 38.7% based on V). Synthesis of 2. 1 (0.03 g, 0.02 mmol) and (nBu4N)Cl (0.01 g, 0.04 mmol) were suspended in N-methyl-2-pyrrolidone (NMP, 5 mL). The reaction mixture was heated to 80 °C for 4 h, whereby the color changed from yellow to green. Diffusion of acetone into the reaction mixture resulted in the formation of emerald-green block crystals of 2. The product was washed with acetone and was air-dried. Yield: 50 mg (0.03 mmol, 62.3% based on V). For further experimental and analytical details, see the Supporting Information.

Figure 1. Illustration of the strontium dodecavanadate in 1. Left: Balland-stick and polyhedral representation of {Sr2V12}. Right: Detailed illustration of the distorted square antiprismatic coordination environment of the cluster-bound Sr2+ ion, highlighting the DMSO “protecting groups”. Color scheme: V/[VO5] = teal, Sr = light blue, Cl = bright green, O = red, S = yellow, C = gray. H atoms are omitted for clarity.

environment (Figure 1). The terminal DMSO ligands shield the cluster from further interactions and result in monomeric species in the solid state. Ligand Exchange-Driven Polymerization of Monomer 1 to Polymer 2. We hypothesized that the exchange of the DMSO ligands for more labile ligands such as dimethylformamide (DMF) or N-methyl pyrrolidone (NMP) could lead to direct assembly of the cluster into supramolecular chains. Thus, we investigated the solution and gas-phase stability as well as the assembly and disassembly mechanisms of 1 by high-resolution cryospray ionization mass spectrometry (HR-CSI-MS).38 For the analysis, a ca. 5 × 10−5 M solution of 1 in DMF was prepared and equilibrated for several hours. Analysis of the data using m/z and isotopic envelope assignments reveals that the parent strontium vanadate cluster anion [Sr2VV12O32Cl]− without the stabilizing DMSO ligands is observed at m/z = 1333.95 (see SI, Table S1). Furthermore, intact cluster units with up to three coordinated DMF ligands are observed under the given experimental conditions ([Sr2VV12O32Cl(dmf)2]−, m/z = 1480.05; [Sr2VV12O32Cl(dmf)3]−, m/z = 1553.10). In addition to the desired solvent exchange of DMSO with DMF, a wide range of oligomeric fragments with up to five cluster units, e.g., {[Sr 2VV 12O 32Cl(dmf)][Sr 2V V12 O32Cl(dmf) 3]4 } 5− (m/z = 1523.88), are observed, see Figure 2 and Table S3 in the SI for additional details. Based on these promising results and the experimental observation of oligomerization in solution, we examined the full polymerization of 1 by reaction of 1 with DMF. Indeed, we were able to isolate a solid product; however, despite significant efforts, no high-quality single crystals could be obtained due to virtually no diffraction. To overcome this issue, we opted to replace DMF with the related solvent Nmethyl pyrrolidone (NMP). Reaction of 1 with NMP at 80 °C in the presence of tetra-n-butyl ammonium chloride (to facilitate crystallization) and diffusion of acetone into the reaction mixture gave emerald-green block crystals suitable for single-crystal X-ray diffraction. X-ray diffraction of the isolated compound 2 gave the monoclinic space group P 21/c with cell

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RESULTS AND DISCUSSION Synthesis and Characterization of the Monomer 1. Here, we explore the possibility of linking individual {V12} units into supramolecular chains, similar to a classical organic polymerization. To avoid additional complexities arising from the use of redox-active linkage metal ions, we opted to use strontium-functionalized dodecavanadates, as in previous studies we had successfully linked decavanadate clusters using Sr2+ cations.30 The strontium-functionalized {V12} was obtained as a single crystalline product by reaction of (nBu4N)3[H3V10O28] with SrCl2·6 H2O in dimethyl sulfoxide (DMSO) and subsequent diffusion crystallization (yield: 38.7%). Single-crystal X-ray diffraction analysis gave the formula H[Sr2V12O32Cl(dmso)8] (1). The presence of one proton on the cluster was inferred from charge balance considerations. However, the proton position was not identified by crystallography. Compound 1 crystallizes in the tetragonal space group P42212 with cell axes a = b = 13.3987(9) Å, c = 18.2616(13) Å, and angles α = β = γ = 90.0°, V = 3278.4(5) Å3 (for crystallographic details see the SI, section 3). The crystal lattice of 1 consists of strontium dodecavanadate clusters, which are stabilized by DMSO ligands. The vanadium oxide framework is virtually identical with previous structures and consists of 12 [VO5] square pyramids in a belt-shaped arrangement which leads to two hexagonal metal binding sites (Figure 1).34,36,37 VO bond lengths are in the expected in the range as reported previously (VOterminal ∼ 1.58−1.61 Å; VObridging ∼ 1.83−1.98 Å).34,36,37 In 1, the binding sites in 1 are occupied by Sr2+ ions, which are covalently bound to four bridging μ2-oxo ligands of the vanadium oxide cluster (dSr−O = 2.67−2.68 Å), and in addition feature four coordinated DMSO ligands, resulting in a distorted square antiprismatic coordination B

DOI: 10.1021/acs.inorgchem.9b01665 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 2. High-resolution cryospray ionization mass spectrometry of 1. Left: Mass spectrum of [Sr2VV12O32Cl(dmf)3]− showing experimental and simulated isotopic patterns. Right: Mass spectrometry of 1 in the m/z range 1300−1600, showing multinuclear cluster fragments. Proposed chain fragments are shown for illustration purposes only. Conditions: solvent = DMF, [cluster] = ca. 5 × 10−5 M. Color scheme: see Figure 1.

Figure 3. (a) Ball-and-stick and polyhedral illustration of the strontium dodecavanadate chains in 2. (b) Orientation of 1D chain assemblies in 2 along the crystallographic a axis. (c) Crystal packing observed in 2. Color scheme: see Figure 1.

parameters a = 10.9360(3) Å, b = 29.5293(9) Å, c = 28.4759(9) Å, α = γ = 90.0°, β = 95.4177(9) Å, and V = 9154.7(5) Å3. Structural analysis of 2 shows the successful polymerization of the strontium dodecavanadate monomers into infinite 1D chains (Figure 3 and SI, Section 3.2). In detail, neighboring Sr-functionalized vanadates are linked by four μ2-bridging NMP ligands. Each Sr2+ ion forms three coordinative bonds to the NMP ligands (dSr−O(NMP) = 2.52− 2.56 Å). In consequence, infinite linear 1D strontium vanadium oxide chains are formed. The three bridging NMP ligands are aligned in a coplanar fashion, and the nonpolar pyrrolidine backbones are pointing away from the chain

assembly, see Figure 3. In the crystal lattice, the chains align parallel and show opposite directions of propagation along the crystallographic a-axis. Notably, adjacent chains are separated by charge-balancing tetrabutyl ammonium cations, and the remaining voids are filled with NMP molecules, see Figure 3c. Charge balance considerations and characteristic UV−vis-NIR signals (intervalence charge-transfer centered at ∼900 nm, see SI, Figure S2) suggest that 2 was reduced in situ upon thermal decomposition of the solvent and contains one reduced VIV center. This behavior has been observed previously for vanadate clusters assembled in organic solvent at elevated temperature.39,40 C

DOI: 10.1021/acs.inorgchem.9b01665 Inorg. Chem. XXXX, XXX, XXX−XXX

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Macroionic Self-Assembly. Angew. Chem., Int. Ed. 2018, 57 (15), 4067−4072. (5) Miras, H. N. H. N.; Cooper, G. J. T. G. J. T.; Long, D.-L.; Bögge, H.; Müller, A.; Streb, C.; Cronin, L. Unveiling the Transient Template in the Self-Assembly of a Molecular Oxide Nanowheel. Science 2010, 327 (5961), 72−74. (6) Toma, F. M.; Sartorel, A.; Iurlo, M.; Carraro, M.; Parisse, P.; MacCato, C.; Rapino, S.; Gonzalez, B. R.; Amenitsch, H.; Da Ros, T.; et al. Efficient Water Oxidation at Carbon Nanotubeg-Polyoxometalate Electrocatalytic Interfaces. Nat. Chem. 2010, 2 (10), 826−831. (7) Ji, Y.; Huang, L.; Hu, J.; Streb, C.; Song, Y. PolyoxometalateFunctionalized Nanocarbon Materials for Energy Conversion, Energy Storage and Sensor Systems. Energy Environ. Sci. 2015, 8 (3), 776− 789. (8) Miras, H. N.; Vilà-Nadal, L.; Cronin, L. Polyoxometalate Based Open-Frameworks (POM-OFs). Chem. Soc. Rev. 2014, 43 (16), 5679−5699. (9) Li, X.-X.; Wang, Y.-X.; Wang, R.-H.; Cui, C.-Y.; Tian, C.-B.; Yang, G.-Y. Designed Assembly of Heterometallic Cluster Organic Frameworks Based on Anderson-Type Polyoxometalate Clusters. Angew. Chem., Int. Ed. 2016, 55 (22), 6462−6466. (10) Dolbecq, A.; Mialane, P.; Sécheresse, F.; Keita, B.; Nadjo, L. Functionalized Polyoxometalates with Covalently Linked Bisphosphonate, N-Donor or Carboxylate Ligands: From Electrocatalytic to Optical Properties. Chem. Commun. 2012, 48 (67), 8299. (11) Qin, J.-S.; Du, D.-Y.; Guan, W.; Bo, X.-J.; Li, Y.-F.; Guo, L.-P.; Su, Z.-M.; Wang, Y.-Y.; Lan, Y.-Q.; Zhou, H.-C. Ultrastable Polymolybdate-Based Metal−Organic Frameworks as Highly Active Electrocatalysts for Hydrogen Generation from Water. J. Am. Chem. Soc. 2015, 137 (22), 7169−7177. (12) Nohra, B.; El Moll, H.; Rodriguez Albelo, L. M.; Mialane, P.; Marrot, J.; Mellot-Draznieks, C.; O’Keeffe, M.; Ngo Biboum, R.; Lemaire, J.; Keita, B.; et al. Polyoxometalate-Based Metal Organic Frameworks (POMOFs): Structural Trends, Energetics, and High Electrocatalytic Efficiency for Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2011, 133 (34), 13363−13374. (13) Macdonell, A.; Johnson, N. A. B.; Surman, A. J.; Cronin, L. Configurable Nanosized Metal Oxide Oligomers via Precise “Click” Coupling Control of Hybrid Polyoxometalates. J. Am. Chem. Soc. 2015, 137 (17), 5662−5665. (14) Khan, M. I.; Yohannes, E.; Doedens, R. J. [M3V18O42(H2O)12(XO4)]·24 H2O (M = Fe, Co; X = V, S): Metal Oxide Based Framework Materials Composed of Polyoxovanadate Clusters. Angew. Chem., Int. Ed. 1999, 38 (9), 1292−1294. (15) Khan, M. I.; Yohannes, E.; Doedens, R. J.; Tabussum, S.; Cevik, S.; Manno, L.; Powell, D. Framework Materials Containing Polyoxovanadates As Building Units: Synthesis and Characterization of (N2H5)2[M3(H2O)12V18O42(EO4)]X24 H2O (M = Mg, Ca) And Li6[Mn3(H2O)12V18O42(EO4)]X24 H2O (E = V, S). Cryst. Eng. 1999, 2 (2−3), 171−179. (16) Streb, C.; Tsunashima, R.; MacLaren, D. A.; McGlone, T.; Akutagawa, T.; Nakamura, T.; Scandurra, A.; Pignataro, B.; Gadegaard, N.; Cronin, L. Supramolecular Silver Polyoxometalate Architectures Direct the Growth of Composite Semiconducting Nanostructures. Angew. Chem., Int. Ed. 2009, 48 (35), 6490−6493. (17) Abbas, H.; Streb, C.; Pickering, A. L.; Neil, A. R.; Long, D. L.; Cronin, L. Molecular Growth of Polyoxometalate Architectures Based on [-Ag{Mo 8}Ag-] Synthons: Toward Designed Cluster Assemblies. Cryst. Growth Des. 2008, 8 (2), 635−642. (18) Wilson, E. F.; Abbas, H.; Duncombe, B. J.; Streb, C.; Long, D.L.; Cronin, L. Probing the Self-Assembly of Inorganic Cluster Architectures in Solution with Cryospray Mass Spectrometry: Growth of Polyoxomolybdate Clusters and Polymers Mediated by Silver(I) Ions. J. Am. Chem. Soc. 2008, 130 (42), 13876−13884. (19) Thiel, J.; Ritchie, C.; Miras, H. N.; Streb, C.; Mitchell, S. G.; Boyd, T.; Corella Ochoa, M. N.; Rosnes, M. H.; McIver, J.; Long, D.L.; Cronin, L.; et al. Modular Inorganic Polyoxometalate Frameworks Showing Emergent Properties: Redox Alloys. Angew. Chem., Int. Ed. 2010, 49 (39), 6984−6988.

SUMMARY In sum, we present the development of a solvent-driven polymerization of single-source strontium vanadium oxides. The monomeric strontium dodecavanadate cluster H[Sr2V12O32Cl(dmso)8] can easily be converted into 1D infinite chains by a solvent-driven deprotection and assembly scheme where the protective DMSO ligands are exchanged for less shielding DMF or NMP ligands, resulting in the formation of oligomeric species in solution and infinite 1D polymers in the solid state. Mass spectrometric studies revealed oligomeric fragments with up to five linked cluster units in solution. Future work will explore the deposition of these chains on substrates as a means generating and immobilizing nanostructured, 1D polyoxometalate species with possible applications in redox activity and oxidation catalysis.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b01665. Instrumentation; synthetic section; crystallographic section; mass spectrometry; and related figures and tables (PDF) Accession Codes

CCDC 1901772−1901773 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Ivana Ivanović-Burmazović: 0000-0002-1651-3359 Carsten Streb: 0000-0002-5846-1905 Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Funding

C.S. gratefully acknowledges the Deutsche Forschungsgemeinschaft DFG (STR1164/4, STR1164/12) and Ulm University for financial support. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Pope, M. T. Heteropoly and Isopoly Oxometalates 1983, 8, 1. (2) Pope, M. T.; Müller, A. Polyoxometalate Chemistry: An Old Field with New Dimensions in Several Disciplines. Angew. Chem., Int. Ed. Engl. 1991, 30 (1), 34−48. (3) Cronin, L.; Mü ller, A. From serendipity to design of polyoxometalates at the nanoscale, aesthetic beauty and applications. Chem. Soc. Rev. 2012, 41 (22), 7333−7648. (4) Luo, J.; Chen, K.; Yin, P.; Li, T.; Wan, G.; Zhang, J.; Ye, S.; Bi, X.; Pang, Y.; Wei, Y.; et al. Effect of Cation−π Interaction on D

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Determined by Ancillary Ligands. J. Am. Chem. Soc. 2015, 137 (42), 13588−13593. (39) Seliverstov, A.; Streb, C. A New Class of Homogeneous VisibleLight Photocatalysts: Molecular Cerium Vanadium Oxide Clusters. Chem. - Eur. J. 2014, 20 (31), 9733−9738. (40) Tucher, J.; Peuntinger, K.; Margraf, J. T.; Clark, T.; Guldi, D. M.; Streb, C. Template-Dependent Photochemical Reactivity of Molecular Metal Oxides. Chem. - Eur. J. 2015, 21 (24), 8716−8719.

(20) Song, Y.-F.; Abbas, H.; Ritchie, C.; Mcmillian, N.; Long, D.-L.; Gadegaard, N.; Cronin, L. From polyoxometalate building blocks to polymers and materials: the silver connection. J. Mater. Chem. 2007, 17, 1903. (21) Mcglone, T.; Streb, C.; Busquets-Fité, M.; Yan, J.; Gabb, D.; Long, D.-L.; Cronin, L. Silver Linked Polyoxometalate Open Frameworks (Ag-POMOFs) for the Directed Fabrication of Silver Nanomaterials. Growth Des 2011, 11, 2471−2478. (22) Mitchell, S. G.; Streb, C.; Miras, H. N.; Boyd, T.; Long, D.-L.; Cronin, L. Face-Directed Self-Assembly of an Electronically Active Archimedean Polyoxometalate Architecture. Nat. Chem. 2010, 2 (4), 308−312. (23) Zhao, C.; Glass, E. N.; Chica, B.; Musaev, D. G.; Sumliner, J. M.; Dyer, R. B.; Lian, T.; Hill, C. L. All-Inorganic Networks and Tetramer Based on Tin(II)-Containing Polyoxometalates: Tuning Structural and Spectral Properties with Lone-Pairs. J. Am. Chem. Soc. 2014, 136 (34), 12085−12091. (24) Liu, J.-C.; Han, Q.; Chen, L.-J.; Zhao, J.-W.; Streb, C.; Song, Y.F. Aggregation of Giant Cerium−Bismuth Tungstate Clusters into a 3D Porous Framework with High Proton Conductivity. Angew. Chem., Int. Ed. 2018, 57 (28), 8416. (25) Misra, A.; Kozma, K.; Streb, C.; Nyman, M. Beyond Charge Balance: Counter-Cations in Polyoxometalate Chemistry. Angew. Chem., Int. Ed. 2019, 0 (ja), 1 DOI: 10.1002/anie.201905600. (26) Rozanska, X.; Fortrie, R.; Sauer, J. Size-Dependent Catalytic Activity of Supported Vanadium Oxide Species: Oxidative Dehydrogenation of Propane. J. Am. Chem. Soc. 2014, 136 (21), 7751−7761. (27) Dasireddy, V. D. B. C.; Singh, S.; Friedrich, H. B. Activation of N-Octane Using Vanadium Oxide Supported on Alkaline Earth Hydroxyapatites. Appl. Catal., A 2013, 456, 105−117. (28) Lechner, M.; Güttel, R.; Streb, C. Challenges in Polyoxometalate-Mediated Aerobic Oxidation Catalysis: Catalyst Development Meets Reactor Design. Dalton Trans. 2016, 45 (42), 16716− 16726. (29) Kastner, K.; Puscher, B.; Streb, C. Self-Assembly of a Tetrahedral 58-Nuclear Barium Vanadium Oxide Cluster. Chem. Commun. 2013, 49 (2), 140−142. (30) Schwarz, B.; Streb, C. Architectural Control of Urea in Supramolecular 1D Strontium Vanadium Oxide Chains. Dalton Trans. 2015, 44 (9), 4195−4199. (31) Kastner, K.; Streb, C. Solvent-Shielding Allows the SelfAssembly of Supramolecular 1D Barium Vanadate Chains. CrystEngComm 2013, 15 (24), 4948. (32) Long, D.-L. L.; Burkholder, E.; Cronin, L. Polyoxometalate Clusters, Nanostructures and Materials: From Self Assembly to Designer Materials and Devices. Chem. Soc. Rev. 2007, 36 (1), 105− 121. (33) Kastner, K.; Margraf, J. T.; Clark, T.; Streb, C. A Molecular Placeholder Strategy To Access a Family of Transition-MetalFunctionalized Vanadium Oxide Clusters. Chem. - Eur. J. 2014, 20 (38), 12269−12273. (34) Kastner, K.; Forster, J.; Ida, H.; Newton, G. N.; Oshio, H.; Streb, C. Controlled Reactivity Tuning of Metal-Functionalized Vanadium Oxide Clusters. Chem. - Eur. J. 2015, 21 (21), 7686−7689. (35) Kastner, K.; Lechner, M.; Weber, S.; Streb, C. In Situ Assembly, De-Metalation and Induced Repair of a Copper-Polyoxovanadate Oxidation Catalyst. ChemistrySelect 2017, 2 (20), 5542−5544. (36) Anjass, M. H.; Kastner, K.; Nägele, F.; Ringenberg, M.; Boas, J. F.; Zhang, J.; Bond, A. M.; Jacob, T.; Streb, C. Stabilization of LowValent Iron(I) in a High-Valent Vanadium(V) Oxide Cluster. Angew. Chem., Int. Ed. 2017, 56 (46), 14749−14752. (37) Kastner, K.; Lechner, M.; Weber, S.; Streb, C. In Situ Assembly, De-Metalation and Induced Repair of a Copper-Polyoxovanadate Oxidation Catalyst. ChemistrySelect 2017, 2 (20), 5542−5544. (38) Vikse, K. L.; Khairallah, G. N.; Ariafard, A.; Canty, A. J.; O’Hair, R. A. J. Gas-Phase and Computational Study of Identical Nickel- and Palladium-Mediated Organic Transformations Where Mechanisms Proceeding via MII or MIV Oxidation States Are E

DOI: 10.1021/acs.inorgchem.9b01665 Inorg. Chem. XXXX, XXX, XXX−XXX