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1. Coinage Metal Complexes of a Sterically Encumbered Anionic Pyridylborate

   https://doi.org/10.1002/chem.202401204  

   Vanga, Mukundam; Muñoz‐Castro, Alvaro; Dias, H_V_Rasika (June 2024, Chemistry – A European Journal)

   Abstract Sterically loaded, anionic pyridine has been synthesized and utilized successfully in the stabilization of a isoleptic series of coinage metal complexes. The treatment of [4‐(Ph₃B)‐2,6‐Trip₂Py]K (Trip=2,4,6‐ⁱPr₃C₆H₂) with CuBr(PPh₃), AgCl(PPh₃) or AuCl(PPh₃) (Py=pyridine) afforded the corresponding [4‐(Ph₃B)‐2,6‐Trip₂Py]M(PPh₃) (M=Au, Ag, Cu) complexes, via salt metathesis, as isolable, crystalline solids. Notably, these reactions avoid the facile single electron transfer chemistry reported with the less bulky ligand systems. The X‐ray structures revealed that they are two‐coordinate metal adducts. The M−N and M−P bond distances are longest in the silver and shortest in the copper adduct among the three group 11 family members. Computational analysis revealed an interesting stability dependence on steric bulk of the anionic pyridine (i. e., pyridyl borate) ligand. A comparison of structures and bonding of [4‐(Ph₃B)‐2,6‐Trip₂Py]Au(PPh₃) to pyridine andm‐terphenyl complexes, {[2,6‐Trip₂Py]Au(PPh₃)}[SbF₆] and [2,6‐Trip₂Ph]Au(PPh₃) are also provided. The Au(I) isocyanide complex, [4‐(Ph₃B)‐2,6‐Trip₂Py]Au(CNBu^t) has been stabilized using the same anionic pyridylborate illustrating that it can support other gold‐ligand moieties as well. 

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2. Solid-state ¹¹ B NMR studies of coinage metal complexes containing a phosphine substituted diboraanthracene ligand

   https://doi.org/10.1039/d1dt02981a  

   Huynh, Winn; Taylor, Jordan W.; Harman, W. Hill; Conley, Matthew P. (October 2021, Dalton Transactions)

   Transition metal interactions with Lewis acids (M → Z linkages) are fundamentally interesting and practically important. The most common Z-type ligands contain boron, which contains an NMR active 11 B nucleus. We measured solid-state 11 B{ 1 H} NMR spectra of copper, silver, and gold complexes containing a phosphine substituted 9,10-diboraanthracene ligand (B 2 P 2 ) that contain planar boron centers and weak M → BR 3 linkages ([(B 2 P 2 )M][BAr F 4 ] (M = Cu (1), Ag (2), Au (3)) characterized by large quadrupolar coupling ( C Q ) values (4.4–4.7 MHz) and large span ( Ω ) values (93–139 ppm). However, the solid-state 11 B{ 1 H} NMR spectrum of K[Au(B 2 P 2 )] − (4), which contains tetrahedral borons, is narrow and characterized by small C Q and Ω values. DFT analysis of 1–4 shows that C Q and Ω are expected to be large for planar boron environments and small for tetrahedral boron, and that the presence of a M → BR 3 linkage relates to the reduction in C Q and 11 B NMR shielding properties. Thus solid-state 11 B NMR spectroscopy contains valuable information about M → BR 3 linkages in complexes containing the B 2 P 2 ligand. 

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3. 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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4. Aromatic character of [Au ₁₃ ] ⁵⁺ and [MAu ₁₂ ] ^4+/6+ (M = Pd, Pt) cores in ligand protected gold nanoclusters – interplay between spherical and planar σ-aromatics

   https://doi.org/10.1039/C9CP04477A  

   Fedik, Nikita; Boldyrev, Alexander I.; Muñoz-Castro, Alvaro (November 2019, Physical Chemistry Chemical Physics)

   The most characteristic feature of planar π-aromatics is the ability to sustain a long-range shielding cone under a magnetic field oriented in a specific direction. In this article, we showed that similar magnetic responses can be found in σ-aromatic and spherical aromatic systems. For [Au 13 ] 5+ , long-range characteristics of the induced magnetic field in the bare icosahedral core are revealed, which are also found in the ligand protected [Au 25 (SH) 18 ] − model, proving its spherical aromatic properties, also supported by the AdNDP analysis. Such properties are given by the 8-ve of the structural core satisfying the Hirsch 2( N + 1) 2 rule, which is also found in the isoelectronic [M@Au 12 ] 4+ core, a part of the [MAu 24 (SR) 18 ] 2− (M = Pd, Pt) cluster. This contrasts with the [M@Au 12 ] 6+ core in [MAu 24 (SR) 18 ] 0 (M = Pd, Pt), representing 6-ve superatoms, which exhibit characteristics of planar σ-aromatics. Our results support the spherical aromatic character of stable superatoms, whereas the 6-ve intermediate electron counts satisfy the 4 N + 2 rule (applicable for both π- and σ-aromatics), showing the reversable and controlled interplay between 3D spherical and 2D σ-aromatic clusters. 

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5. Cooperative activation of O–H and S–H bonds across the Co–P bond of an N-heterocyclic phosphido complex

   https://doi.org/10.1039/C8DT05052J  

   Poitras, Andrew M.; Bezpalko, Mark W.; Foxman, Bruce M.; Thomas, Christine M. (February 2019, Dalton Transactions)

   Metal–ligand cooperation has proven to be a viable concept for σ bond activation and catalysis, however there are few examples involving phosphorus as an active participant in bond cleavage. The reactivity of E–H bonds (E = S, O) across a metal–phosphorus bond of a cobalt( i ) center ligated by a tridenate N-heterocyclic phosphido (NHP − ) ligand with diphosphine sidearms, (PPP) − , has been explored. Addition of PhOH to (PPP)CoPMe 3 ( 1 ) cleanly affords (PP OPh P)Co(H)PMe 3 ( 2 ), in which the O–H bond was heterolytically cleaved across the M–P NHP bond. Addition of PhSH to 1 first generates (PP H P)Co(SPh)PMe 3 ( 3 ), which undergoes an intermolecular rearrangement to generate (PP SPh P)Co(H)PMe 3 ( 4 ) as the thermodynamic product. A comparison with a related platinum( ii ) system reveals the subtle effects that variations in metal intrinsic properties can have on metal–ligand bifunctional σ bond activation processes. 

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