A crystalline doubly oxidized carbene.

The chemistry of carbon is governed by the octet rule, which refers to its tendency to have eight electrons in its valence shell. However, a few exceptions do exist, for example, the trityl radical (Ph3C∙) (ref. 1) and carbocation (Ph3C+) (ref. 2) with seven and six valence electrons, respectively, and carbenes (R2C:)-two-coordinate octet-defying species with formally six valence electrons3. Carbenes are now powerful tools in chemistry, and have even found applications in material and medicinal sciences4. Can we undress the carbene further by removing its non-bonding electrons? Here we describe the synthesis of a crystalline doubly oxidized carbene (R2C2+), through a two-electron oxidation/oxide-ion abstraction sequence from an electron-rich carbene5. Despite a cumulenic structure and strong delocalization of the positive charges, the dicoordinate carbon centre maintains significant electrophilicity, and possesses two accessible vacant orbitals. A two-electron reduction/deprotonation sequence regenerates the parent carbene, fully consistent with its description as a doubly oxidized carbene. This work demonstrates that the use of bulky strong electron-donor substituents can simultaneously impart electronic stabilization and steric protection to both vacant orbitals on the central carbon atom, paving the way for the isolation of a variety of doubly oxidized carbenes.

Dipolar Coupling as a Mechanism for Fine Control of Magnetic States in ErCOT-Alkyl Molecular Magnets.

The design of molecular magnets has progressed greatly by taking advantage of the ability to impart successive perturbations and control vibronic transitions in 4fn systems through the careful manipulation of the crystal field. Herein, we control the orientation and rigidity of two dinuclear ErCOT-based molecular magnets: the inversion-symmetric bridged [ErCOT(µ-Me)(THF)]2 (2) and the nearly linear Li[(ErCOT)2(µ-Me)3] (3). The conserved anisotropy of the ErCOT synthetic unit facilitates the direction of the arrangement of its magnetic anisotropy for the purposes of generating controlled internal magnetic fields, improving control of the energetics and transition probabilities of the electronic angular momentum states with exchange biasing via dipolar coupling. This control is evidenced through the introduction of a second thermal barrier to relaxation operant at low temperatures that is twice as large in 3 as in 2. This barrier acts to suppress through-barrier relaxation by protecting the ground state from interacting with stray local fields while operating at an energy scale an order of magnitude smaller than the crystal field term. These properties are highlighted when contrasted against the mononuclear structure ErCOT(Bn)(THF)2 (1), in which quantum tunneling of the magnetization processes dominate, as demonstrated by magnetometry and ab initio computational methods. Furthermore, far-infrared magnetospectroscopy measurements reveal that the increased rigidity imparted by successive removal of solvent ligands when adding bridging methyl groups, along with the increased excited state purity, severely limits local spin-vibrational interactions that facilitate magnetic relaxation, manifesting as longer relaxation times in 3 relative to those in 2 as temperature is increased.

Superelectrophilic Nonclassical Carbocations.

The chemistry of dicationic and tricationic 2-norbornyl cations has been studied. A series of N-heterocyclic functionalized norborneol substrates were prepared and ionization of these compounds in superacid provided superelectrophilic species. These highly charged 2-norbornyl cations were found to react with arene nucleophiles in high yields and stereoselectivity. Density functional theory computational studies suggest that increasing positive charge on the structures tends to enhance the degree of nonclassical (or 3-center-2-electron) bonding through separation of the cationic charges.

Genuine carbene versus carbene-like reactivity.

Singlet carbenes are not always isolable and often even elude direct detection. When they escape observation, their formation can sometimes be evidenced by in situ trapping experiments. However, is carbene-like reactivity genuine evidence of carbene formation? Herein, using the first example of a spectroscopically characterized cyclic (amino)(aryl)carbene (CAArC), we cast doubt on the most common carbene trapping reactions as sufficient proof of carbene formation.

Electrochemical Cycling of Redox-Active Boron Cluster-Based Materials in the Solid State.

This work demonstrates the first successful electrochemical cycling of a redox-active boron cluster-based material in the solid state. Specifically, we designed and synthesized an ether-functionalized dodecaborate cluster, B12(OCH3)12, which is the smallest redox-active building block in the B12(OR)12 family. This species can reversibly access four oxidation states in solution, ranging from a dianion to a radical cation. We show that a chemically isolated and characterized neutral [B12(OCH3)12]0 cluster can be utilized as a cathode active material in a PEO-based rechargeable all-solid-state cell with a lithium metal anode. The cell exhibits an impressive active material utilization close to 95% at C/20 rate, a high Coulombic efficiency of 96%, and reversibility, with only 4% capacity fade after 16 days of cycling. This work represents a conceptual departure in the development of redox-active components for electrochemical storage and serves as an entry point to a broader class of borane-based materials.

Molecular Network Approach to Anisotropic Ising Lattices: Parsing Magnetization Dynamics in Er3+ Systems with 0-3-Dimensional Spin Interactivity.

We present a wide-ranging interrogation of the border between single-molecule and solid-state magnetism through a study of erbium-based Ising-type magnetic compounds with a fixed magnetic unit, using three different charge-balancing cations as the means to modulate the crystal packing environment. Properties rooted in the isolated spin Hamiltonian remain fixed, yet careful observation of the dynamics reveals the breakdown of this approximation in a number of interesting ways. First, differences in crystal packing lead to a striking 3 orders of magnitude suppression in magnetic relaxation rates, indicating a rich interplay between intermolecular interactions governed by the anisotropic Ising lattice stabilization and localized slow magnetic relaxation driven by the spin-forbidden nature of quantum tunneling of the f-electron-based magnetization. By means of diverse and rigorous physical methods, including temperature-dependent X-ray crystallography, field, temperature, and time-dependent magnetometry, and the application of a new magnetization fitting technique to quantify the magnetic susceptibility peakshape, we are able to construct a more nuanced view of the role nonzero-dimensional interactions can play in what are predominantly considered zero-dimensional magnetic materials. Specifically, we use low field susceptibility and virgin-curve analysis to isolate metamagnetic spin-flip transitions in each system with a field strength corresponding to the expected strength of the internal dipole-dipole lattice. This behavior is vital to a complete interpretation of the dynamics and is likely common for systems with such high anisotropy. This collective interactivity opens a new realm of possibility for molecular magnetic materials, where their unprecedented localized anisotropy is the determining factor in building higher dimensionality.

Vertex Differentiation Strategy for Tuning the Physical Properties of closo-Dodecaborate Weakly Coordinating Anions.

We report the synthesis and characterization of various compounds containing the 1,7,9-hydroxylated closo-dodecahydrododecaborate (B12H9(OH)32-) cluster motif. Specifically, we show how the parent compound can be synthesized on the multigram scale and further perhalogenated, leading to a new class of vertex-differentiated weakly coordinating anions. We show that a postmodification of the hydroxyl groups by alkylation affords further opportunities for tailoring these anions' stability, steric bulk, and solubility properties. The resulting dodecaborate-based salts were subjected to a full thermal and electrochemical stability evaluation, showing that many of these anions maintain thermal stability up to 500 °C and feature no redox activity below ∼1 V vs Fc/Fc+. Mixed hydroxylated/halogenated clusters show enhanced solubility compared to their purely halogenated analogs and retain weakly coordinating properties in the solid state, as demonstrated by ionic conductivity measurements of their Li+ salts.

Circularly Polarized Luminescence from Cyclic (Alkyl)(Amino) Carbene Derived Propellers.

Organic circularly polarized luminescence (CPL)-active molecular emitters featuring dynamic propeller-like luminophores were prepared in one step from cyclic(alkyl)(amino) carbenes (CAACs). These molecules exhibit through-space arene-arene π-delocalization and rapid intramolecular inter-system crossing (ISC) in line with their helical character.

Structurally Diverse Bench-Stable Nickel(0) Pre-Catalysts: A Practical Toolkit for In Situ Ligation Protocols.

A flurry of recent research has centered on harnessing the power of nickel catalysis in organic synthesis. These efforts have been bolstered by contemporaneous development of well-defined nickel (pre)catalysts with diverse structure and reactivity. In this report, we present ten different bench-stable, 18-electron, formally zero-valent nickel-olefin complexes that are competent pre-catalysts in various reactions. Our investigation includes preparations of novel, bench-stable Ni(COD)(L) complexes (COD=1,5-cyclooctadiene), in which L=quinone, cyclopentadienone, thiophene-S-oxide, and fulvene. Characterization by NMR, IR, single-crystal X-ray diffraction, cyclic voltammetry, thermogravimetric analysis, and natural bond orbital analysis sheds light on the structure, bonding, and properties of these complexes. Applications in an assortment of nickel-catalyzed reactions underscore the complementary nature of the different pre-catalysts within this toolkit.

Intuitive Control of Low-Energy Magnetic Excitations via Directed Dipolar Interactions in a Series of Er(III)-Based Complexes.

Dipolar coupling is rarely invoked as a driving force for slow relaxation dynamics in lanthanide-based single-molecule magnets, though it is often the strongest mechanism available for mediating inter-ion magnetic interactions in such species. Indeed, for multinuclear lanthanide complexes, the magnitude and anisotropy of the dipolar interaction can be considerable given their ability to form highly directional, high-moment ground states. Herein, we present a mono-, di-, and trinuclear erbium-based single-molecule magnet sequence, ([Er-TiPS2COT]+)n (n = 1-3), wherein a drastic reduction in the allowedness of magnetic relaxation pathways is rationalized within the framework of the dipole-dipole interactions between angular momentum quanta. The resulting design principles for multinuclear molecular magnetism arising from intramolecular dipolar coupling interactions between highly anisotropic magnetic states present a nuanced justification of the relaxation dynamics in complex manifolds of individual quantized transitions. Experimental evidence for the validity of this model is provided by coupling the relaxation dynamics to an AC magnetic field across an unprecedented frequency range for molecular magnetism (103-10-5 Hz). The combination of slow dynamics and multiple, low-energy transitions leads to a number of noteworthy phenomena, including a lanthanide single-molecule magnet with three well-defined relaxation processes observable at a single temperature.

Mixed-Isocyanide Complexes of Technetium under Steric and Electronic Control.

Reactions of the alkyl isocyanide fac-[Tc(CO)3(CNR)2Cl] complexes (2) (CNR = CNnBu or CNtBu) with the sterically encumbered isocyanide CNp-FArDarF2 [DArF = 3,5-(CF3)2C6H3] allow a selective exchange of the carbonyl ligands of 2 and the isolation of the mixed-isocyanide complexes mer,trans-[Tc(CNp-FArDarF2)3(CNR)2Cl] (3). Depending on the steric requirements of the residues R, the remaining chlorido ligand can be replaced by another isocyanide ligand. Cationic complexes such as mer-[Tc(CNp-FArDarF2)3(CNnBu)3]+ (4a) or mer,trans-[Tc(CNp-FArDarF2)3(CNnBu)2(CNtBu)]+ (6) have been prepared in this way and isolated as their PF6- salts. mer,trans-[Tc(CNp-FArDarF2)3(CNnBu)2(CNtBu)](PF6) represents to the best of our knowledge the first transition-metal complex with three different isocyanides in its coordination sphere. Since the degree of the ligand exchange seems to be controlled both by the electronic and steric measures of the incoming isocyanides, we undertook similar reactions with the sterically less demanding p-fluorophenyl isocyanide, CNPhpF, which indeed readily led to the hexakis(isocyanide)technetium(I) cation through an exchange of all ligands in the staring materials [Tc2(CO)6(µ-Cl)3]- or fac-[Tc(CO)3(CNR)2Cl]. The influence of the substituents at the isocyanide ligands in such reactions has been reasoned with the density functional theory-derived electrostatic potential at the accessible surface of the corresponding isocyanide carbon atoms.

Crystalline Hydrogen-Bonding Networks and Mixed-Metal Framework Materials Enabled by an Electronically Differentiated Heteroditopic Isocyanide/Carboxylate Linker Group.

Mixed-metal solid-state framework materials are emerging candidates for advanced applications in catalysis and chemical separations. Traditionally, the syntheses of mixed-metal framework systems rely on postsynthetic ion exchange, metalloligands, or metal-deposition techniques for the incorporation of a second metal within a framework material. However, these methods are often incompatible with the incorporation of low-valent metal centers, which preferentially bind to electronically "soft" ligands according to the tenets of hard/soft acid/base theory. Here we present the electronically differentiated isocyanide/carboxylate heteroditopic linker ligand 1,4-CNArMes2C6H4CO2H (TIBMes2H; TIB = terphenyl isocyanide benzoate; ArMes2 = 2,6-(2,4,6-Me3C6H2)2C6H2), which is capable of selective binding of low-valent metals via the isocyano group and complexation of hard Lewis acidic metals through the carboxylate unit. This heteroditopic ligand also possesses an encumbering m-terphenyl backbone at the isocyanide function to foster coordinative unsaturation. The treatment of TIBMes2H with [Cu(NCMe)4]PF6 in a 3:1 ratio results in preferential binding of the isocyanide group to the Cu(I) center as assayed by multinuclear NMR and IR spectroscopies. IR spectroscopy also provides strong evidence for the formation of a copper(I) tris(isocyanide) complex, wherein the carboxylic acid group remains unperturbed. The addition of TIBMes2 to [Cu(NCMe)4]PF6 in a 4:1 ratio results in crystallization of the hydrogen-bonding network, [Cu(TIBMes2H)4]PF6, in which the formation of R22(8) hydrogen bonds results in a 7-fold interpenetrated diamondoid lattice structure. The preassembly of a copper(I) tris(isocyanide) complex using TIBMes2H, followed by deprotonation and the introduction of ZnCl2, generates a novel and unusual zwitterionic solid-state phase (denoted as Cu/Zn-ISOCN-5; ISOCN = isocyanide coordination network) consisting of a coordinatively unsaturated [Cu(CNR)3]+ cationic secondary building unit (SBU) and an anionic, paddlewheel-type Zn(II)-based SBU of the formulation [Cl2Zn2(O2CR)3]-. Inductively coupled plasma mass spectrometry analysis provided firm evidence for a 2:1 Zn-to-Cu ratio in the network, thereby indicating that the isocyanide and carboxylate groups selectively bind soft and hard Lewis acidic metal centers, respectively. The extended structure of Cu/Zn-ISOCN-5 is a densely packed, noninterpenetrated AB-stacked layer network with modest surface area. However, it is thermally robust, and its formation and compositional integrity validate the use of an electronically differentiated linker for the formation of mixed-metal frameworks incorporating low-valent metal centers.

Icosahedral m-Carboranes Containing Exopolyhedral B-Se and B-Te Bonds.

Chalcogen-containing carboranes have been known for several decades and possess stable exopolyhedral B(9)-Se and B(9)-Te σ bonds despite the electron-donating ability of the B(9) vertex. While these molecules are known, little has been done to thoroughly evaluate their electrophilic and nucleophilic behavior. Herein, we report an assessment of the electrophilic reactivity of m-carboranylselenyl(II), -tellurenyl(II), and -tellurenyl(IV) chlorides and establish their reactivity pattern with Grignard reagents, alkenes, alkynes, enolates, and electron-rich arenes. These electrophilic reactions afford unique electron-rich B-Y-C (Y = Se, Te) bonding motifs not commonly found before. Furthermore, we show that m-carboranylselenolate, and even m-carboranyltellurolate, can be competent nucleophiles and participate in nucleophilic aromatic substitution reactions. Arene substitution chemistry is shown to be further extended to electron-rich species via palladium-mediated cross-coupling chemistry.

ReI Tricarbonyl Complexes as Coordinate Covalent Inhibitors for the SARS-CoV-2 Main Cysteine Protease.

Since its outbreak, the severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) has impacted the quality of life and cost hundreds-of-thousands of lives worldwide. Based on its global spread and mortality, there is an urgent need for novel treatments which can combat this disease. To date, the 3-chymotrypsin-like protease (3CLpro ), which is also known as the main protease, is considered among the most important pharmacological targets. The vast majority of investigated 3CLpro inhibitors are organic, non-covalent binders. Herein, the use of inorganic, coordinate covalent binders is proposed that can attenuate the activity of the protease. ReI tricarbonyl complexes were identified that demonstrate coordinate covalent enzymatic inhibition of 3CLpro . Preliminary studies indicate the selective inhibition of 3CLpro over several human proteases. This study presents the first example of metal complexes as inhibitors for the 3CLpro cysteine protease.

Aqueous Stability and Ligand Substitution of a Layered Cu(I)/Isocyanide-Based Organometallic Network Material with a Well-Defined Channel Structure.

Isocyanide coordination networks (ISOCNs), which consist of multitopic isocyanide linker groups and transition-metal-based secondary building units (SBUs), are a promising class of organometallic framework materials for the inclusion of low-valent metal centers as primary structural components. Previously, it was demonstrated that the ditopic m-terphenyl isocyanide ligand, [CNArMes2]2 (ArMes2 = 2,6-(2,4,6-Me3C6H2)2C6H3), could provide single-metal node frameworks based on Cu(I) and Ni(0) centers. However, the relatively short linker length in [CNArMes2]2 precluded the formation of networks with significant porosity. Here, it is shown that expansion of the [CNArMes2]2 scaffold with a central phenylene spacer allows for the formation of a robust Cu(I)-based framework with a distinct and solvent accessible channel structure. This new framework, denoted Cu-ISOCN-4, is prepared as single-crystalline samples from a solvothermal reaction between [Cu(NCMe)4]PF6 and expanded linker 1,4-(CNArMes2)2C6H4. Crystallographic characterization of Cu-ISOCN-4 revealed mononuclear [Cu(THF)(CNR)3]+ structural nodes. The expanded diisocyanide linker results in fourfold interpenetrated (6,3) internal morphology. However, interpenetration in Cu-ISOCN-4 results in discrete layer domains, each of which possesses well-defined 29 × 19 Å channels along the crystallographic b axis. Thermogravimetric analysis on Cu-ISOCN-4 revealed THF solvent loss from the channels between 100-200 °C and dissociation of the Cu-coordinated THF ligand at 290 °C. The overall integrity of the network remains intact up to 400 °C, thereby signifying the robust nature of materials produced from metal-isocyanide M-C linkages. Aqueous stability studies revealed that Cu-ISOCN-4 remains chemically resistant to exposure to liquid water for several days. In addition, ligand exchange studies in both THF and aqueous solution demonstrate that the Cu-coordinated THF group in Cu-ISOCN-4 can be readily substituted with pyridine. This ligand exchange process occurs via single-crystal-to-single-crystal transformations and can also be readily monitored by infrared spectroscopy.

Cation-Controlled Assembly of Polyoxotungstate-Based Coordination Networks.

The Preyssler polyoxoanion, [NaP5 W30 O110 ]14- ({P5 W30 }), is used as a platform for evaluating the role of nonbridging cations in the formation of transition-metal-bridged polyoxometalate (POM) coordination frameworks. Specifically, the assembly architecture of Co2+ -bridged frameworks is shown to be dependent on the identity and amount of alkali or alkaline-earth cations present during crystallization. The inclusion of Li+ , Na+ , K+ , Mg2+ , or Ca2+ in the framework synthesis is used to selectively synthesize five different Co2+ -bridged {P5 W30 } structures. The influence of the competition between K+ and Co2+ for binding to {P5 W30 } in dictating framework assembly is evaluated. The role of ion pairing on framework assembly structure and available void volume is discussed. Overall, these results provide insight into factors governing the ability to achieve controlled assembly of POM-based coordination networks.

Understanding the Activity and Enantioselectivity of Acetyl-Protected Aminoethyl Quinoline Ligands in Palladium-Catalyzed ß-C(sp3)-H Bond Arylation Reactions.

Chiral acetyl-protected aminoalkyl quinoline (APAQ) ligands were recently discovered to afford highly active and enantioselective palladium catalysts for the arylation of methylene C(sp3)-H bonds, and herein, we investigate the origins of these heightened properties. Unprecedented amide-bridged APAQ-Pd dimers were predicted by density functional theory (DFT) calculations and were confirmed by single-crystal X-ray diffraction studies. Comparison of structural features between APAQ-Pd complexes and an acetyl-protected aminoethylpyridine APAPy-Pd complex strongly suggests that the high activity of the former originates from the presence of the quinoline ring, which slows the formation of the off-cycle palladium dimer. Furthermore, steric topographic maps for a representative subset of monomeric, monoligated palladium complexes allowed us to draw a unique parallel between the three-dimensional structures of these catalysts and their reported asymmetric induction in ß-C(sp3)-H bond arylation reactions. Finally, cooperative noncovalent interactions present between the APAQ ligand and the substrate were identified as a crucial factor for imparting selectivity between chemically equivalent methylenic C(sp3)-H bonds prior to concerted metalation deprotonation activation.

Tunable Metal Oxide Frameworks via Coordination Assembly of Preyssler-Type Molecular Clusters.

We present the synthesis of metal oxide frameworks composed of [NaP5W30O110]14- assembled with Mn, Fe, Co, Ni, Cu, or Zn bridging metal ions. X-ray diffraction shows that the frameworks adopt the same assembly regardless of bridging metal ion. Furthermore, our synthesis allows for the assembly of isostructural frameworks with mixed-metal ion bridges, or with clusters that have been doped with Mo, providing a high degree of compositional diversity. This consistent assembly enables investigation into the role of the building blocks in the properties of the metal oxide frameworks. The presence of bridging metal ions leads to increased conductivity compared to unbridged frameworks, and frameworks bridged with Fe have the highest conductivity. Additionally, Mo-doping can be used to enhance the conductivities of the frameworks. Similar structures can be obtained from clusters in which the central Na+ has been replaced with Bi3+ or Sm3+. Overall, the optical and electronic properties are tunable via choice of bridging metal ion and cluster building block and reveal emergent properties in these cluster-based frameworks. These results demonstrate the promise of using polyoxometalate clusters as building blocks for tunable complex metal oxide materials with emergent properties.

Electrocatalytic H2O Reduction with f-Elements: Mechanistic Insight and Overpotential Tuning in a Series of Lanthanide Complexes.

Electrocatalytic energy conversion with molecular f-element catalysts is still in an early phase of its development. We here report detailed electrochemical investigations on the recently reported trivalent lanthanide coordination complexes [((Ad,MeArO)3mes)Ln] (1-Ln), with Ln = La, Ce, Pr, Nd, Sm, Gd, Dy, Er, and Yb, which were now found to perform as active electrocatalysts for the reduction of water to dihydrogen. Reactivity studies involving complexes 1-Ln and the Ln(II) analogues [K(2.2.2-crypt)][((Ad,MeArO)3mes)Ln] (2-Ln) suggest a reaction mechanism that differs significantly from the reaction pathway found for the corresponding uranium catalyst [((Ad,MeArO)3mes)U] (1-U). While complexes 1-Ln activate water via a radical pathway, only upon a 1 e- reduction to yield the reduced species 2-Ln, the 5f analogue 1-U directly reduces H2O via a 2 e- pathway. The electrocatalytic H2O reduction by complexes 1-Ln is initiated by the respective Ln(III)/Ln(II) redox couples, which gradually turn to more positive values across the Ln series. This correlation has been exploited to tune the catalytic overpotential of water reduction by choice of the lanthanide ion. Kinetic studies of the 1-Ln series were performed to elucidate correlations between overpotential and turnover frequencies of the 4f-based electrocatalysts.

Using Diamagnetic Yttrium and Lanthanum Complexes to Explore Ligand Reduction and C-H Bond Activation in a Tris(aryloxide)mesitylene Ligand System.

[Y(N(SiMe3)2)3] reacts with (Ad,MeArOH)3mes to form the Y3+ complex [((Ad,MeArO)3mes)Y], 1-Y. This complex reacts with potassium metal in the presence of 2.2.2-cryptand to give a cocrystallized mixture of [K(2.2.2-cryptand)][((Ad,MeArO)3mes)Y], 2-Y, and [K(2.2.2-cryptand)][((Ad,MeArO)3mes)YH], 3-Y. The electron paramagnetic resonance spectrum of this crystalline mixture exhibits an isotropic signal at 77 K ( giso = 2.000, Wiso = 1.8 mT), suggesting that 2-Y is best described as a Y3+ complex of the tris(aryloxide)mesitylene radical ((Ad,MeArO)3mes)4-. Evidence of the hydride ligand in 3-Y was obtained by 89Y-1H heteronuclear multiple quantum coherence NMR spectroscopy, and a coupling constant of JYH = 93 Hz was observed. A single crystal of 3-Y was also obtained in pure form and structurally characterized for comparison with the crystal data on the mixed component 2-Ln/3-Ln crystals. The origin of the hydride in 3-Ln is unknown, but further studies of the reduction of 1-La, previously found to form 2-La, revealed a possible source. Ligand-based C-H bond activation and loss of hydrogen can occur under reducing conditions to form a tetraanionic ligand derived from ((Ad,MeArO)3mes)3-, as observed in [K(2.2.2-cryptand)][((Ad,MeArO)3(C6Me3(CH2)2CH)La], 4-La.