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1. Cationic Bis(Gold) Indenyl Complexes

   https://doi.org/10.1002/cplu.202300691  

   Slinger, Brady_L; Zhu, Jiaqi; Widenhoefer, Ross_A (February 2024, ChemPlusChem)

   Abstract Reaction of (P)AuOTf [P=P(t‐Bu)₂o‐biphenyl] with indenyl‐ or 3‐methylindenyl lithium led to isolation of gold η¹‐indenyl complexes (P)Au(η¹‐inden‐1‐yl) (1 a) and (P)Au(η¹‐3‐methylinden‐1‐yl) (1 b), respectively, in >65 % yield. Whereas complex1 bis static, complex1 aundergoes facile, degenerate 1,3‐migration of gold about the indenyl ligand (ΔG^≠_153K=9.1±1.1 kcal/mol). Treatment of complexes1 aand1 bwith (P)AuNTf₂led to formation of the corresponding cationic bis(gold) indenyl complexestrans‐[(P)Au]₂(η¹,η¹‐inden‐1,3‐yl) (2 a) andtrans‐[(P)Au]₂(η¹,η²‐3‐methylinden‐1‐yl) (2 b), respectively, which were characterized spectroscopically and modeled computationally. Despite the absence of aurophilic stabilization in complexes2 aand2 b, the binding affinity of mono(gold) complex1 atoward exogenous (P)Au⁺exceed that of free indene by ~350‐fold and similarly the binding affinity of1 btoward exogenous (P)Au⁺exceed that of 3‐methylindene by ~50‐fold. The energy barrier for protodeauration of bis(gold) indenyl complex2 awith HOAc was ≥8 kcal/mol higher than for protodeauration of mono(gold) complex1 a. 

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2. Cationic cerium(IV) complexes with multiple open coordination sites

   https://doi.org/10.1016/j.jorganchem.2017.10.017  

   Solola, Lukman A.; Carroll, Patrick J.; Schelter, Eric J. (February 2018, Journal of Organometallic Chemistry)
3. Syntheses and Structures of Cationic Bis(gold) Cyclopentadienyl Complexes

   https://doi.org/10.1021/acs.organomet.4c00436  

   Slinger, Brady L; Malek, Jack C; Widenhoefer, Ross A (December 2024, Organometallics)
4. Synthesis, Characterization, and Reactivity of Cationic Gold Diarylallenylidene Complexes

   https://doi.org/10.1002/anie.201713209  

   Kim, Nana; Widenhoefer, Ross A. (March 2018, Angewandte Chemie International Edition)

   Abstract Methoxide abstraction from gold acetylide complexes of the form (L)Au[η¹‐C≡CC(OMe)ArAr′] (L=IPr, P(^tBu)₂(ortho‐biphenyl); Ar/Ar′=C₆H₄X where X=H, Cl, Me, OMe) with trimethylsilyl trifluoromethanesulfonate (TMSOTf) at −78 °C resulted in the formation of the corresponding cationic gold diarylallenylidene complexes [(L)Au=C=C=CArAr′]⁺ OTf⁻in ≥85±5 % yield according to¹H NMR analysis.¹³C NMR and IR spectroscopic analysis of these complexes established the arene‐dependent delocalization of positive charge on both the C1 and C3 allenylidene carbon atoms. The diphenylallenylidene complex [(IPr)Au=C=C=CPh₂]⁺ OTf⁻reacted with heteroatom nucleophiles at the allenylidene C1 and/or C3 carbon atom. 

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5. Cucurbit[8]uril forms tight inclusion complexes with cationic triamantanes

   https://doi.org/10.1039/D3NJ00156C  

   King, David; Šumanovac, Tatjana; Murkli, Steven; Schreiner, Peter R.; Šekutor, Marina; Isaacs, Lyle (March 2023, New Journal of Chemistry)

   We report the synthesis of quaternary (di)cationic triamantane derivatives G1 and G3 by the permethylation of the corresponding primary ammonium ions G2 and G4. The complexation behaviors of G1–G4 toward CB[7] and CB[8] were examined by 1 H NMR spectroscopy, which reveals that CB[8] is capable of fully encapsulating G1–G4 whereas CB[7] forms inclusion complexes with G1, G2, and G4 but cannot fully encapsulate the central hydrophobic core of the bis-quaternary ammonium ion G3. The geometries of the CB[ n ]-guest complexes were determined by analyzing the complexation induced changes in chemical shifts and were further confirmed by molecular modelling using the Conformer–Rotamer Ensemble Sampling Tool (CREST) based on the GFN methods. Finally, the complexation thermodynamics were determined by a combination of 1 H NMR competitive experiments, direct isothermal titration calorimetry (ITC) measurements, and competitive ITC titrations using a tight binding ternary complex as a competitor. 

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