Living cationic polymerization of vinyl ethers and styrene derivatives: Design of initiating systems based on added salts with halogen anions

This paper overviews three living cationic polymerization systems (for styrene, p-methoxystyrene, and isobutyl vinyl ether) that are, in common, featured by: (i) specifically in nonpolar solvents, the use of the hydrogen halide/metal halide initiating systems (HX/MX_n; X: I, Br, Cl; MX_n: ZnX₂, SnCl₄), which generate a living growing carbocation stabilized by a nucleophilic counteranion (X⁻…MX_n); (ii) specifically in polar solvents, the use of externally added ammonium salts (nBu₄N⁺Y⁻; Y⁻: I⁻, Br⁻, Cl⁻), which permit the generation of living species from HX/MX_n by providing nucleophilic halogen anions Y⁻, either the same as or different from the halogen X⁻ in HX.     

Structures,Bonding Analyses and Reactivity of a Dicationic Digallene and Diindene Mimicking trans-bent Ditetrylenes

The reaction of bisdicyclohexylphosphinoethane (dcpe) and the subvalent M^I sources [M^I(PhF)₂][pf] (M=Ga⁺, In⁺; [pf]⁻=[Al(OR^F)₄]⁻; R^F=C(CF₃)₃) yielded the salts [{M(dcpe)}₂][pf]₂, containing the first dicationic, trans-bent digallene and diindene structures reported so far. The non-classical M^I⇆M^I double bonds are surprisingly short and display a ditetrylene-like structure. The bonding situation was extensively analyzed by quantum chemical calculations, QTAIM (Quantum Theory of Atoms in Molecules) and EDA-NOCV (Energy Decomposition Analysis with the combination of Natural Orbitals for Chemical Valence) analyses and is compared to that in the isoelectronic and isostructural, but neutral digermenes and distannenes. The dissolved [{Ga(dcpe)}₂]²⁺([pf]⁻)₂ readily reacts with 1-hexene, cyclooctyne, diphenyldisulfide, diphenylphosphine and under mild conditions at room temperature. This reactivity is analyzed and rationalized.     

A three‐dimensional framework of bis­[tris­(ethyl­enediamine)zinc] tetra­iodo­cadmate diiodide assisted by N—H⋯I hydrogen bonds

The title salt, [Zn(C₂N₂H₈)₃]₂[CdI₄]I₂, conventionally abbreviated [Zn(en)₃]₂[CdI₄]I₂, where en is ethyl­enediamine, contains discrete [Zn(en)₃]²⁺ cations and [CdI₄]²⁻ anions with distorted octa­hedral and nearly tetra­hedral geometries, respectively, as well as uncoordinated I⁻ ions. The cation and the free I⁻ anion lie on twofold rotation axes and the [CdI₄]²⁻ anion lies on a axis in the space group I2d. The structure exhibits numerous weak inter‐ionic hydrogen bonds of two types, viz. N—H⋯I⁻(free ion) and N—H⋯I([CdI₄]²⁻), which support the resulting three‐dimensional framework.     

Rational Synthesis,Structures and Properties of the Ionic Liquid Binary Iodine-Bromine Octahalide Series [InBr8−n]2− (n=0, 2, 3, 4)

A series of octanuclear iodine-bromine interhalides [I_nBr_8−n]²⁻ (n=0, 2, 3, 4) were prepared systematically in two steps. Firstly, addition of a dihalogen (Br₂ or IBr) to the triaminocyclopropenium bromide salt [C₃(NEt₂)₃]Br forms the corresponding trihalide salt with Br₃⁻ or IBr₂⁻ anions, respectively. Secondly, addition to Br₃⁻ of half an equivalent of Br₂ gives the octabromine polyhalide [Br₈]²⁻, whereas addition to IBr₂⁻ of half an equivalent of Br₂, IBr or I₂ gives the corresponding interhalides: [I₂Br₆]²⁻, [I₃Br₅]²⁻, and [I₄Br₄]²⁻, respectively. The four octahalides were characterized by X-ray crystallography, computational studies, Raman and Far-IR spectroscopies, as well as by TGA and melting point. All of the salts were found to be ionic liquids.     

Trapping a Silicon(I) Radical with Carbenes: A Cationic cAAC–Silicon(I) Radical and an NHC–Parent-Silyliumylidene Cation

The trapping of a silicon(I) radical with N-heterocyclic carbenes is described. The reaction of the cyclic (alkyl)(amino) carbene [cAAC_Me] (cAAC_Me=:C(CMe₂)₂(CH₂)NAr, Ar=2,6-iPr₂C₆H₃) with H₂SiI₂ in a 3:1 molar ratio in DME afforded a mixture of the separated ion pair [(cAAC_Me)₂Si:^.]⁺I⁻ ( 1 ), which features a cationic cAAC–silicon(I) radical, and [cAAC_Me−H]⁺I⁻. In addition, the reaction of the NHC–iodosilicon(I) dimer [I_Ar(I)Si:]₂ (I_Ar=:C{N(Ar)CH}₂) with 4 equiv of I_Me (:C{N(Me)CMe}₂), which proceeded through the formation of a silicon(I) radical intermediate, afforded [(I_Me)₂SiH]⁺I⁻ ( 2 ) comprising the first NHC–parent-silyliumylidene cation. Its further reaction with fluorobenzene afforded the C_Ar−H bond activation product [1-F-2-I_Me-C₆H₄]⁺I⁻ ( 3 ). The isolation of 2 and 3 confirmed the reaction mechanism for the formation of 1 . Compounds 1 – 3 were analyzed by EPR and NMR spectroscopy, DFT calculations, and X-ray crystallography.     

Trapping a Silicon(I) Radical with Carbenes: A Cationic cAAC–Silicon(I) Radical and an NHC–Parent‐Silyliumylidene Cation

The trapping of a silicon(I) radical with N‐heterocyclic carbenes is described. The reaction of the cyclic (alkyl)(amino) carbene [cAAC_Me] (cAAC_Me=:C(CMe₂)₂(CH₂)NAr, Ar=2,6‐i Pr₂C₆H₃) with H₂SiI₂ in a 3:1 molar ratio in DME afforded a mixture of the separated ion pair [(cAAC_Me)₂Si:^.]⁺I⁻ ( 1 ), which features a cationic cAAC–silicon(I) radical, and [cAAC_Me−H]⁺I⁻. In addition, the reaction of the NHC–iodosilicon(I) dimer [I_Ar(I)Si:]₂ (I_Ar=:C{N(Ar)CH}₂) with 4 equiv of I_Me (:C{N(Me)CMe}₂), which proceeded through the formation of a silicon(I) radical intermediate, afforded [(I_Me)₂SiH]⁺I⁻ ( 2 ) comprising the first NHC–parent‐silyliumylidene cation. Its further reaction with fluorobenzene afforded the C_Ar−H bond activation product [1‐F‐2‐I_Me‐C₆H₄]⁺I⁻ ( 3 ). The isolation of 2 and 3 confirmed the reaction mechanism for the formation of 1 . Compounds 1 – 3 were analyzed by EPR and NMR spectroscopy, DFT calculations, and X‐ray crystallography.     

Sequential Transformation of Zirconium(IV)‐MOFs into Heterobimetallic MOFs Bearing Magnetic Anisotropic Cobalt(II) Centers

Heterometallic metal–organic frameworks (MOFs) allow the precise placement of various metals at atomic precision within a porous framework. This new level of control by MOFs promises fascinating advances in basic science and application. However, the rational design and synthesis of heterometallic MOFs remains a challenge due to the complexity of the heterometallic systems. Herein, we show that bimetallic MOFs with MX₂(INA)₄ moieties (INA=isonicotinate; M=Co²⁺ or Fe²⁺; X=OH^?, Cl^?, Br^?, I^?, NCS^?, or NCSe^?) can be generated by the sequential modification of a Zr‐based MOF. This multi‐step modification not only replaced the linear organic linker with a square planar MX₂(INA)₄ unit, but also altered the symmetry, unit cell, and topology of the parent structure. Single‐crystal to single‐crystal transformation is realized so that snapshots for transition process were captured by successive single‐crystal X‐ray diffraction. Furthermore, the installation of Co(NCS)₂(INA)₄ endows field‐induced slow magnetic relaxation property to the diamagnetic Zr‐MOF.     

Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag+/X2 (X=Cl,Br, I) System

The synergistic Ag⁺/X₂ system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X₂ or Ag⁺ alone. Intermediates for its action may include [Ag_m(X₂)_n]^m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I₂‐Ag( A ), [Ag₂(I₂)₄]²⁺( A ⁻)₂ and [Ag₂(I₂)₆]²⁺( A ⁻)₂⋅(I₂)_x≈0.65 form by reaction of Ag( A ) ( A =Al(OR^F)₄; R^F=C(CF₃)₃) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I₂‐Ag( A ) is ideally set up to act as a 2 e⁻ oxidant with stoichiometric formation of 2 AgI and 2 A ⁻. Preliminary reactivity tests proved this ( A )Ag‐I₂‐Ag( A ) starting material to oxidize n‐C₅H₁₂, C₃H₈, CH₂Cl₂, P₄ or S₈ at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF₆ (M=4d metals). This suggests that ( A )Ag‐I₂‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.     

Phosphine-substituted Cubane Clusters with the Mo3S4Ga Core

The reaction of cationic clusters [Mo₃S₄(Dppet)₃X₃]X (I; Dppet = cis-1,2-bis(diphenylphosphino)ethylene; X = Cl, Br) with gallium metal in tetrahydrofuran (THF) affords cubane-like clusters [Mo₃S₄(GaX)(Dppet)₃X₃] (IIa, X = Cl; IIb, X = Br). In the synthesis of IIb, the crystals of the cationic cluster [Mo₃S₄(Dppet)₃Br₃](GaBr₄) (III) were isolated from the mother liquor. The structures of complexes IIa ? 1.5THF, IIb ? 1.5THF, III ? 1.625THF, and [Mo₃S₄(Dppe)₃Br₃](GaBr₄) ? 2THF (IV ? 2THF; Dppe = 1,2-bis(diphenylphosphino)ethane) were established by X-ray diffraction (CIF files CCDC № 1851341–1851344).

     

Protonation and Hydrogenation Experiments with Iridium(0) and Iridium(−1) tropp Complexes: Formation of Hydrides

The reactions of three different tetracoordinated Ir complexes, [Ir(tropp^ph)₂]ⁿ (n=+1, 0, −1), which differ in the formal oxidation state of the metal from +1 to −1, with proton sources and dihydrogen were investigated (tropp=5‐(diphenylphosphanyl)dibenzo[a,d]cycloheptene). It was found that the cationic 16‐electron complex [Ir(tropp^ph)₂]⁺ ( 2 ) cannot be protonated but reacts with NaBH₄ to the very stable 18‐electron Ir^I hydride [IrH(tropp^ph)₂] ( 5 ), which is further protonated with medium strong acids to give the 18‐electron Ir^III dihydride [IrH₂(tropp^ph)₂]⁺ ( 6 ; pK_s in CH₂Cl₂/THF/H₂O 1 : 1 : 2 ca. 2.2). Both, the neutral 17‐electron Ir⁰ complex [Ir(tropp^ph)₂] ( 3 ) and the anionic 18‐electron complex [Ir(tropp^ph)₂]⁻ ( 4 ) react rapidly with H₂O to give the monohydride 5 . In reactions of 3 with H₂O, the terminal Ir^I hydroxide [Ir(OH)(tropp^ph)₂] ( 8 ) is formed in equal amounts. All these complexes, apart from 5 , which is inert, do react rapidly with dihydrogen. The complex 2 gives the dihydride 6 in an oxidative addition reaction, while 3 , 4 , and 8 give the monohydride 5 . Interestingly, a salt‐type hydride (i.e., LiH) is formed as further product in the unexpected reaction with [Li(thf)_x]⁺[Ir(tropp^ph)₂]⁻ ( 4 ). Because 3 undergoes disproportionation into 2 and 4 according to 2 3 ⇄ 2 + 4 (K_disp=2.7⋅10⁻⁵), it is likely that actually the diamagnetic species and not the odd‐electron complex 3 is involved in the reactions studied here, and possible mechanisms for these are discussed.     

[Ni(cod)2][Al(ORF)4], a Source for Naked Nickel(I) Chemistry

The straightforward synthesis of the cationic, purely organometallic Ni^I salt [Ni(cod)₂]⁺[Al(OR^F)₄]⁻ was realized through a reaction between [Ni(cod)₂] and Ag[Al(OR^F)₄] (cod=1,5‐cyclooctadiene). Crystal‐structure analysis and EPR, XANES, and cyclic voltammetry studies confirmed the presence of a homoleptic Ni^I olefin complex. Weak interactions between the metal center, the ligands, and the anion provide a good starting material for further cationic Ni^I complexes.     

Aluminum(III) Cations [(NHC) ⋅ AlMes2]+: Synthesis,Characterization, and Application in FLP-Chemistry

The three-coordinate aluminum cations ligated by N-heterocyclic carbenes (NHCs) [(NHC) ⋅ AlMes₂]⁺[B(C₆F₅)₄]⁻ (NHC=IMe^Me 4 , IiPr^Me 5 , IiPr 6 , Mes=2,4,6-trimethylphenyl) were prepared via hydride abstraction of the alanes (NHC) ⋅ AlHMes₂ (NHC=IMe^Me 1 , IiPr^Me 2 , IiPr 3 ) using [Ph₃C]⁺[B(C₆F₅)₄]⁻ in toluene as hydride acceptor. If this reaction was performed in diethyl ether, the corresponding four-coordinate aluminum etherate cations [(NHC) ⋅ AlMes₂(OEt₂)]⁺ [B(C₆F₅)₄]⁻ 7 – 9 (NHC=IMe^Me 7 , IiPr^Me 8 , IiPr 9 ) were isolated. According to a theoretical and experimental assessment of the Lewis-acidity of the [(IMe^Me) ⋅ AlMes₂]⁺ cation is the acidity larger than that of B(C₆F₅)₃ and of similar magnitude as reported for Al(C₆F₅)₃. The reaction of [(IMe^Me) ⋅ AlMes₂]⁺[B(C₆F₅)₄]⁻ 4 with the sterically less demanding, basic phosphine PMe₃ afforded a mixed NHC/phosphine stabilized cation [(IMe^Me) ⋅ AlMes₂(PMe₃)]⁺[B(C₆F₅)₄]⁻ 10 . Equimolar mixtures of 4 and the sterically more demanding PCy₃ gave a frustrated Lewis-pair (FLP), i.e., [(IMe^Me) ⋅ AlMes₂]⁺[B(C₆F₅)₄]⁻/PCy₃ FLP-11 , which reacts with small molecules such as CO₂, ethene, and 2-butyne.     

Template Assembly of Polyiodide Networks at Complexed Metal Cations: Synthesis and Structures of [Pd2Cl2([18]aneN2S4)]1.5I5(I3)2 and [K([15]aneO5)2]I9

The cations [Pd ₂ Cl ₂ L] ²⁺ and [KL ₂ ^{′ +} (L = [18]aneN₂S₄, L′ =[15]aneO₅) have been used as templates for the synthesis of unique three-dimensional polyiodide networks. The metal cations in [Pd₂Cl₂L]_1.5I₅(I₃)₂ are linked into infinite chains by pairwise hydrogen bonding; the resulting cationic polymers run through channels formed by the extended polyiodide network. [KL₂^′]I₉ shows a three-dimensional network of puckered cubic cages of I₉⁻ ions whose cavities are occupied by the metal cations (section from the structure shown on the right).     

Front Cover: Safe Entry to Ag(I)/Ag(III) Mixed Valence Salts Containing the Homoleptic Ag(III) Anion [Ag(CF3)4]− (Eur. J. Inorg. Chem. 19/2023)

The synthesis of Naumann's Ag^I/Ag^III mixed valence salt [Ag^I]⁺[Ag^III(CF₃)₄]⁻ ( Ag-1 ) is revisited. Ag-1 is now safely available in half gram scale upon 2e⁻ oxidation of AgF in presence of CF₃SiMe₃ and ambient air. In addition to its unprecedented crystallographic characterization, the use of Ag-1 to build the novel Ag^I/Ag^III salts [ Ag (bpy)₂] -1 , [ Ag (18-crown-6)₂] -1 , [ Ag -crypt-222] -1 and [ Ag (PCy₃)₂] -1 is herein reported, alongside their characterization by NMR, single crystal X-ray diffraction (Sc-XRD) and elemental analysis (EA). The utility of the currently affordable Ag-1 in gold(I) catalysis was demonstrated by the excellent catalytic activity displayed by [{ Au (PPh₃)}₂(μ-Cl)] -1 and [ Au (PPh₃)] -1 in the 5-exo-dig cyclization of N-propargylbenzamide ( 2 ). These cationic Au^I catalysts are accessible from (PPh₃)AuCl and Ag-1 , and outperform the activity of the well-known benchmark catalyst (PPh₃)AuNTf₂.     

Poly[tetraamminecopper(II) bis[tris(μ2‐cyanido‐κ2C,N)dicuprate(I)]]: a unique CuI–CuII mixed‐valence complex containing anionic cuprous cyanide layers and [Cu(NH3)4]2+ cations

The title compound, {[Cu(NH₃)₄][Cu(CN)₃]₂}_n, features a Cu^I–Cu^II mixed‐valence CuCN framework based on {[Cu₂(CN)₃]⁻}_n anionic layers and [Cu(NH₃)₄]²⁺ cations. The asymmetric unit contains two different Cu^I ions and one Cu^II ion which lies on a centre of inversion. Each Cu^I ion is coordinated to three cyanide ligands with a distorted trigonal–planar geometry, while the Cu^II ion is ligated by four ammine ligands, with a distorted square‐planar coordination geometry. The interlinkage between Cu^I ions and cyanide bridges produces a honeycomb‐like {[Cu₂(CN)₃]⁻}_n anionic layer containing 18‐membered planar [Cu(CN)]₆ metallocycles. A [Cu(NH₃)₄]²⁺ cation fills each metallocyclic cavity within pairs of exactly superimposed {[Cu₂(CN)₃]⁻}_n anionic layers, but there are no cations between the layers of adjacent pairs, which are offset. Pairs of N—H...N hydrogen‐bonding interactions link the N—H groups of the ammine ligands to the N atoms of cyanide ligands.     

Reaction of cationic palladium(II) and rhodium(I) complexes with the t-butylperoxy anion: Preparation of t-butylperoxo-palladium(II) and -rhodium(I) complexes

Treatment of the coordinatively unsaturated cationic complexes, [(η-C₃H₅)(Ph₃P)₂Pd^II]PF₆ and [(1,5-COD)₂Rh^I]BF₄, with potassium t-butylperoxide in dichloromethane gives the t-butylperoxometal complexes; (η-C₃H₅)(Ph₃P)(t-BuOO)Pd^II and [(1,5-COD)(t-BuOO)Rh^I](KBF₄), via nucleophilic attack by t-BuOO⁻ on the cationic metal center.     

Diamondoid framework solid with Sn(OCH3)2–tetrapyridylporphyrin linkers,CuI nodes and [CuICl2]− counter‐ions

We report on the synthesis of a new metal–organic framework (MOF) composed of Sn(OCH₃)₂–tetrakis(pyridin‐4‐yl)porphyrin linkers, Cu⁺ connecting nodes and [CuCl₂]⁻ counter‐ions, namely poly[[bis(methanolato‐κO)[μ₅‐5,10,15,20‐tetrakis(pyridin‐4‐yl)porphyrin‐κ⁸1κN⁵:1′κN¹⁰:1′′κN¹⁵:1′′′κN²⁰:2κ⁴N²¹,N²²,N²³,N²⁴]copper(I)tin(II)] dichloridocuprate(I)], [CuSn(C₄₀H₂₄N₈)(CH₃O)₂][CuCl₂]. Its crystal structure consists of a single‐framework coordination polymer of the organic ligand and the Cu^I ions. The latter are characterized by a tetrahedral coordination geometry [with CN (coordination number) = 4], linking to the pyridyl N‐atom sites of four different ligands and imparting to the positively charged polymeric assembly a diamondoid PtS‐type topology. Correspondingly, every porphyrin unit is coordinated to four different Cu^I connectors. The [CuCl₂]⁻ anions occupy the intra‐lattice voids, along with disordered molecules of the water crystallization solvent. The asymmetric unit of this structure consists of two halves of the porphyrin scaffold, located on centres of crystallographic inversion, and the Cu⁺ and [CuCl₂]⁻ ions. This report provides unique structural evidence for the formation of tetrapyridylporphyrin‐based three‐dimensional MOFs with a diamondoid architecture that have been observed earlier only on rare occasions.     

A charge-separation-type ionic solid composed of hexanuclear complexes with a macrocyclic tetragold(I) metalloligand

The reaction of Na[Co^III(d -ebp)] (d -H₄ebp = N,N′-ethylenebis[d -penicillamine]) with [(Au^ICl)₂(dppe)] (dppe = 1,2-bis[diphenylphosphino]ethane) gave a cationic Au^I₄Co^III₂ hexanuclear complex, [Co^III₂(L^Au4)]²⁺ ([ 1 ]²⁺), where [L^Au4]⁴⁻ is a cyclic tetragold(I) metalloligand with a 32-membered ring, [Au^I₄(dppe)₂(d -ebp)₂]⁴⁻. Complex [ 1 ]²⁺ crystallized with NO₃⁻ to produce a charge-separation (CS)-type ionic solid of [ 1 ](NO₃)₂. In [ 1 ](NO₃)₂, the complex cations are assembled to form cationic supramolecular hexamers of {[ 1 ]²⁺}₆, which are closely packed in a face-centered cubic (fcc) lattice structure. The nitrate anions of [ 1 ](NO₃)₂ were accommodated in hydrophilic and hydrophobic tetrahedral interstices of the fcc structure to form tetrameric and hexameric nitrate clusters of {NO₃⁻}₄ and {NO₃⁻}₆, respectively. An analogous CS-type ionic solid formulated as [Ni^IICo^III(L^Au4)](NO₃) ([ 2 ](NO₃)) was obtained when a 1:1 mixture of Na[Co^III(d -ebp)] and [Ni^II(d -H₂ebp)] was reacted with [(Au^ICl)₂(dppe)], accompanied by the conversion of the diamagnetic, square-planar [Ni^II(d -H₂ebp)] to the paramagnetic, octahedral [Ni^II(d -ebp)]²⁻. While the overall fcc structure in [ 2 ](NO₃) was similar to that of [ 1 ](NO₃)₂, none of the nitrate anions were accommodated in any hydrophobic tetrahedral interstice, reflecting the difference in the complex charges between [ 1 ]²⁺ and [ 2 ]⁺.     

Substituent Effect to Fine-Tune Energy Levels of Atom-Precise [MoOS3]2− Modified Copper(I) Thiolate Clusters Boosting Recyclable Photocatalysis

The propulsion of photocatalytic hydrogen (H₂) production is limited by the rational design and regulation of catalysts with precise structures and excellent activities. In this work, the [MoOS₃]²⁻ unit is introduced into the Cu^I clusters to form a series of atomically-precise Mo^VI−Cu^I bimetallic clusters of [Cu₆(MoOS₃)₂(C₆H₅(CH₂)S)₂(P(C₆H₄−R)₃)₄] ⋅ xCH₃CN (R=H, CH₃, or F), which show high photocatalytic H₂ evolution activities and excellent stability. By electron push-pull effects of the surface ligand, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of these Mo^VI−Cu^I clusters can be finely tuned, promoting the resultant visible-light-driven H₂ evolution performance. Furthermore, Mo^VI−Cu^I clusters loaded onto the surface of magnetic Fe₃O₄ carriers significantly reduced the loss of catalysts in the collection process, efficiently addressing the recycling issues of such small cluster-based catalyst. This work not only highlights a competitively universal approach on the design of high-efficiency cluster photocatalysts for energy conversion, but also makes it feasible to manipulate the catalytic performance of clusters through a rational substituent strategy.     

Fine Tuning of MOF‐505 Analogues To Reduce Low‐Pressure Methane Uptake and Enhance Methane Working Capacity

We present a crystal engineering strategy to fine tune the pore chemistry and CH₄‐storage performance of a family of isomorphic MOFs based upon PCN‐14. These MOFs exhibit similar pore size, pore surface, and surface area (around 3000 m² g⁻¹) and were prepared with the goal to enhance CH₄ working capacity. [Cu₂(L2)(H₂O)₂]_n (NJU‐Bai 41: NJU‐Bai for Nanjing University Bai's group), [Cu₂(L3)(H₂O)₂]_n (NJU‐Bai 42), and [Cu₂(L4)(DMF)₂]_n (NJU‐Bai 43) were prepared and we observed that the CH₄ volumetric working capacity and volumetric uptake values are influenced by subtle changes in structure and chemistry. In particular, the CH₄ working capacity of NJU‐Bai 43 reaches 198 cm³ (STP: 273.15 K, 1 atm) cm⁻³ at 298 K and 65 bar, which is amongst the highest reported for MOFs under these conditions and is much higher than the corresponding value for PCN‐14 (157 cm³ (STP) cm⁻³).