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1. Structural Evidence for Pnictogen-Centered Lewis Acidity in Cationic Platinum-Stibine Complexes Featuring Pendent Amino or Ammonium Groups

   https://doi.org/10.3390/molecules26071985  

   Rodrigues, Roberta R.; Gabbaï, François P. (April 2021, Molecules)

   null (Ed.)

   As part of our continuing interest in the chemistry of cationic antimony Lewis acids as ligands for late transition metals, we have now investigated the synthesis of platinum complexes featuring a triarylstibine ligand substituted by an o-[(dimethylamino)methyl]phenyl group referred to as ArN. More specifically, we describe the synthesis of the amino stibine ligand Ph2SbArN (L) and its platinum dichloride complex [LPtCl]Cl which exists as a chloride salt and which shows weak coordination of the amino group to the antimony center. We also report the conversion of [LPtCl]Cl into a tricationic complex [LHPt(SMe2)]3+ which has been isolated as a tris-triflate salt after reaction of [LPtCl]Cl with SMe2, HOTf and AgOTf. Finally, we show that [LHPt(SMe2)][OTf]3 acts as a catalyst for the cyclization of 2-allyl-2-(2-propynyl)malonate. 

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2. An η ³ ‐Bound Allyl Ligand on Magnesium in a Mechanochemically Generated Mg/K Allyl Complex

   https://doi.org/10.1002/anie.201916410  

   Koby, Ross F.; Doerr, Alicia M.; Rightmire, Nicholas R.; Schley, Nathan D.; Long, Brian K.; Hanusa, Timothy P. (June 2020, Angewandte Chemie International Edition)

   Abstract Milling two equivalents of K[1,3‐(SiMe₃)₂C₃H₃] (=K[A′]) with MgX₂(X=Cl, Br) produces the allyl complex [K₂MgA′₄] (1). Crystals grown from toluene are of the solvated species [((η⁶‐tol)K)₂MgA′₄] ([1⋅2(tol)]), a trimetallic monomer with both bridging and terminal (η¹) allyl ligands. When recrystallized from hexanes, the unsolvated1forms a 2D coordination polymer, in which the Mg is surrounded by three allyl ligands. The C−C bond lengths differ by only 0.028 Å, indicating virtually complete electron delocalization. This is an unprecedented coordination mode for an allyl ligand bound to Mg. DFT calculations indicate that in isolation, an η³‐allyl configuration on Mg is energetically preferred over the η¹‐ (σ‐bonded) arrangement, but the Mg must be in a low coordination environment for it to be experimentally realized. Methyl methacrylate is effectively polymerized by1, with activities that are comparable to K[A′] and greater than the homometallic magnesium complex [{MgA′₂}₂]. 

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3. Iron(II) Complexes Featuring a Redox‐Active Dihydrazonopyrrole Ligand

   https://doi.org/10.1002/zaac.202100097  

   Jesse, Kate A.; Chang, Mu‐Chieh; Filatov, Alexander S.; Anderson, John S. (June 2021, Zeitschrift für anorganische und allgemeine Chemie)

   Abstract Nature uses control of the secondary coordination sphere to facilitate an astounding variety of transformations. Similarly, synthetic chemists have found metal‐ligand cooperativity to be a powerful strategy for designing complexes that can mediate challenging reactivity. In particular, this strategy has been used to facilitate two electron reactions with first row transition metals that more typically engage in one electron redox processes. While NNN pincer ligands feature prominently in this area, examples which can potentially engage in both proton and electron transfer are less common. Dihydrazonopyrrole (DHP) ligands have been isolated in a variety of redox and protonation states when complexed to Ni. However, the redox‐state of this ligand scaffold is less obvious when complexed to metal centers with more accessible redox couples. Here, we synthesize a new series of Fe‐DHP complexes in two distinct oxidation states. Detailed characterization supports that the redox‐chemistry in this set is still primarily ligand based. Finally, these complexes exist as 5‐coordinate species with an open coordination site offering the possibility of enhanced reactivity. 

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4. Introducing the Bis(mesitoyl)phosphide Ligand into Dinuclear Trivalent Rare Earth Metal Coordination Chemistry

   https://doi.org/10.1002/cplu.202400311  

   Deshapriya, Saroshan; Delano, IV, Francis; Demir, Selvan (August 2024, ChemPlusChem)

   Abstract Anionic ancillary ligands play a critical role in the construction of rare earth (RE) metal complexes due to the large influence on the stability of the molecule and engendering emergent electronic properties that are of interest in a plethora of applications. Supporting ligands comprising oxygen donor atoms are highly pursued in RE chemistry owing to the high oxophilicity innate to these ions. The scarcely employed bis(acyl)phosphide (BAP) ligands feature oxygen coordination sites and contain a phosphide backbone rendering it attractive for RE‐coordination chemistry. Here, we integrate bis(mesitoyl)phosphide (^mesBAP) as an ancillary ligand into RE^IIIchemistry to generate the first dinuclear trivalent RE complexes containing BAP ligands; [{^mesBAP}₂RE(THF)(μ‐Cl)]₂(RE=Y, (1), Gd (2), and Dy (3); THF=tetrahydrofuran). Each RE center is ligated to two monoanionic^mesBAP ligands, one THF molecule and one chloride ion. All three molecules were characterized through single‐crystal X‐ray diffraction,³¹P NMR, IR and UV‐Vis spectroscopy.³¹P,¹H and¹³C NMR on the diamagnetic yttrium congener1confirm asymmetric ligand coordination. DFT calculations conducted on2provided insight into the electronic structure. The magnetic properties of2and3were investigated via SQUID magnetometry. The Gd^IIIions exhibit weak antiferromagnetic coupling, corroborated by DFT results. 

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5. Earth Abundant Oxidation Catalysts for Removal of Contaminants of Emerging Concern from Wastewater: Homogeneous Catalytic Screening of Monomeric Complexes

   https://doi.org/10.3390/molecules28186466  

   Garcia, Leslie; Koper, Makynna R.; Mondal, Somrita; Priddle, Joshua T.; Truong, William A.; Allbritton, Elisabeth M.; McAdoo, Ashtyn G.; Cannon-Smith, Desiray J.; Funwie, Neil L.; Hoang, Tuyet; et al (September 2023, Earth Abundant Oxidation Catalysts for Removal of Contaminants of Emerging Concern from Wastewater: Homogeneous Catalytic Screening of Monomeric Complexes)

   Pellegrini, M; Saccani, C; Guzzini, A (Ed.)

   Twenty novel Mn, Fe, and Cu complexes of ethylene cross-bridged tetraazamacrocycles with potentially copolymerizable allyl and benzyl pendant arms were synthesized and characterized. Multiple X-ray crystal structures demonstrate the cis-folded pseudo-octahedral geometry forced by the rigidifying ethylene cross-bridge and show that two cis coordination cites are available for interaction with substrate and oxidant. The Cu complexes were used to determine kinetic stability under harsh acidic and high-temperature conditions, which revealed that the cyclam-based ligands provide superior stabilization with half-lives of many minutes or even hours in 5 M HCl at 50–90 °C. Cyclic voltammetry studies of the Fe and Mn complexes reveal reversible redox processes indicating stabilization of Fe2+/Fe3+ and Mn2+/Mn3+/Mn4+ oxidation states, indicating the likelihood of catalytic oxidation for these complexes. Finally, dye-bleaching experiments with methylene blue, methyl orange, and rhodamine B demonstrate efficient catalytic decolorization and allow selection of the most successful monomeric catalysts for copolymerization to produce future heterogeneous water purification materials. 

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