Heptanuclear Cluster Research Articles

Restriction of reaction sites on metal-sulfide cores induced by steric repulsion of bis-N-heterocyclic carbene ligands in trinuclear complexes bearing triply bridging sulfide ligands.

Mixed-ligand and mixed-metal trinuclear complexes bearing two {Pt-bisNHC-C1} moieties, [{Pt(bisNHC-C1)}2(ML)(μ3-S)2] n+ (ML = Pt(bisNHC-C2), n = 2; ML = Pt(bisNHC-C3), n = 2; ML = Rh(cod), n = 1; ML = RhCp*, n = 2), where bisNHC-C1, bisNHC-C2 and bisNHC-C3 represent methylene-, ethylene- and propylene-bridged bis-NHC ligands, respectively, were synthesised and structurally characterised. Reactions of these complexes with a half eq. of Ag(i) ions were examined using 1H and 195Pt NMR spectroscopy. The results exhibit that the trinuclear complexes react with Ag(i) ions accompanied by the formation of Ag-Pt bonds with the {Pt-bisNHC-C1} moieties in the first step affording corresponding heptanuclear complexes except for the RhCp* complex. The RhCp* complex gave a tetranuclear complex bearing the trinuclear unit with an Ag(i) ion. Further addition of Ag(i) ions for the other complexes resulted in disassembling of the heptanuclear clusters affording tetranuclear complexes confirmed by the observation of exchange of the Ag(i) ions in 195Pt NMR measurements, which exhibited signals with no coupling to Ag nuclei.

Heptanuclear Mixed-Valence Co4IIICo3II Molecular Wheel─A Molecular Analogue of Layered Double Hydroxides with Single-Molecule Magnet Behavior and Electrocatalytic Activity for Hydrogen Evolution Reactions.

We present a bifunctional heptanuclear cobalt(II)/cobalt(III) molecular complex formulated as [Co7(μ3-OH)4(H2L1)2(HL2)2](NO3)6·6H2O (1) (where H5L1 is 2,2'-(((1E,1'E)-((2-hydroxy-5-methyl-1,3-phenylene)bis(methanylylidene))bis(azanylylidene))bis(propane-1,3-diol)) and H2L2 is 2-amino-1,3-propanediol). Compound 1 has been characterized by single-crystal X-ray diffraction analysis along with other spectral and magnetic measurements. Structural analysis indicates that 1 contains a mixed-valence Co7 cluster where a central Co(II) ion is connected to six different Co centers (four CoIII and two CoII ions) by four μ3-OH groups, giving rise to a planar heptanuclear cluster that resembles a molecular fragment of a layered double hydroxide (LDH). Two triply deprotonated (H2L1)3- ligands form the outer side of the cluster while two singly deprotonated (HL2)- ligands are located at the top and bottom of the central heptanuclear core. Variable temperature magnetic measurements indicate the presence of weak ferromagnetic CoII···CoII interactions (J = 3.53(6) cm-1) within the linear trinuclear CoII cluster. AC susceptibility measurements show that 1 is a field-induced single-molecule magnet (SMM) with τ0 = 8.2(7) × 10-7 s and Ueff = 11.3(4) K. The electrocatalytic hydrogen evolution reaction (HER) activity of 1 in homogeneous phase shows an overpotential of 455 mV, with a Faradaic efficiency of 81% and a TOF of 8.97 × 104 μmol H2 h-1 mol-1.

Iso- and hetero-polyoxovanadium glycolates [VIV6O6(glyc)6MIII(OH)6]3- (M = V, Cr, Fe, and Al) encapsulating metal hydroxides.

Polyoxovanadium glycolates (NH4)3[V6O6(glyc)6V(μ-OH)6]·10H2O (1-V7) (H2glyc = glycolic acid) and its derivatives added with ammonium sulfates (NH4)3[V6O6(glyc)6M(μ-OH)6][(NH4)2SO4]2·xH2O (M = Cr, x = 6, 2-CrV6; M = Fe, x = 7, 3-FeV6; M = Al, x = 6, 4-AlV6) were obtained through self-assembly and fully characterized. Compounds 1-4 are composed of the same fully reduced cyclic {VIV6O6} unit bridged by six glycolate ligands. The framework encapsulated an octahedral metal(III) hydroxide {M(OH)6} (M = V3+, Cr3+, Fe3+, and Al3+) in the center, forming an iso- or hetero-heptanuclear Anderson-type structure. Moreover, two sulfate anions capped the two sides of cyclic {V6O6} units in compounds 2-4. Each sulfate formed a strong triple hydrogen bond (2.657-2.829 Å) with the μ3-OH group of the hydroxide. The sulfate anions played important roles in the formation of layered structures in 2-4, while the clusters were stacked compactly through strong hydrogen bonds in 1-V7. Because of the different central metals, these heptanuclear clusters exhibited distinct electronic structures as well as redox and magnetic properties. Magnetic studies showed that compounds 1-3 exhibited weak antiferromagnetic interactions in decreasing order with Fe3+, V3+ and Cr3+, while 4-AlV6 displayed weak ferromagnetic interactions. Their relationships with the local environment of the FeV-cofactor in V-nitrogenase are also discussed.

A new multifunctional anionic 3D Zn(ii)-MOF based on heptanuclear clusters: selective adsorption of organic dyes and a dual-emitting sensor for nitroantibiotics

A new multifunctional Zn-MOF (1) based on heptanuclear clusters was synthesized, which can adsorb cationic dyes selectively and serve as a dual-emission sensor for sensitive detection of nitrofuran antibiotics via luminescence quenching process.

Selective formation of dinuclear and heptanuclear Zn(II), Ni(II), and Co(II) metal clusters from a simple dialdehyde

Herein, the selective formation of dinuclear and hexagonal disk-shape heptanuclear metal cluster complexes is reported. The reaction of 4-tert-butyl-2,6-diformylphenol (L) and M(ClO4)2, where M is Zn (II), Co (II), or Ni (II), in the presence of a strong base resulted in the formation of heptanuclear metal cluster complexes. Treatment of M(ClO4)2·6H2O (M = Zn, and Ni) in the presence of NaOCH3 in MeOH at the elevated temperature afforded [Zn2(L)2(CH3O)4].ClO4 (1) and [Ni2(L)2(CH3O)2].ClO4 (2). Furthermore, treatment of M(ClO4)2·6H2O (M = Zn, Co, and Ni) in the presence of NaOH in MeOH at the elevated temperature yielded heptanuclear metal cluster complexes [Zn7(L)6(µ3-CH3O)6]·2ClO4 (3), [Co7(L)6(µ3-CH3O)6]·2ClO4 (4), and [Ni7(L)6(µ3-OH)6]·2ClO4 (5). These were characterized using elemental analysis, infrared spectroscopy, and X-ray crystallography. Zinc complexes 1 and 3 were also characterized using 1H NMR spectroscopy. In the crystal structures of heptanuclear cluster complexes 3–5, six ligand molecules were aligned to hold six metal centers that were in hexagonal positions. The central metal atom was connected by the bridging of the oxygen atom of methoxy and hydroxy groups with the remaining metal atoms. The photophysical properties of complexes were studied and zinc complexes 1 and 3 showed strong fluorescence in PL spectra. Themetal cluster complexes 1, 3 and 4 were employed as catalysts in the cycloaddition reaction of CO2 to epoxide, exhibiting moderate activities.

Exploring the influence of counter anions on the structure and magnetic properties of two classical Ni7 disk-like clusters

We present the synthesis, characterization of two heptanuclear coordination nickel(II) clusters: [Ni7(bicH)6]·0.5[NiCl4]·Cl·12H2O (1) and [Ni7(bicH)6]·2NO3 (2), in which bicH3 = N,N-bis(2-hydroxyethyl)glycine. They consist of analogous structural disk-like cores that are constructed by Ni(II) ions and structure directing ligand bicH (doubly deprotonated form of bicH3). They have different magnetic properties. Whereas there is the absence of the out of phase ac susceptibility (χ′′) for compound 1, compound 2 has slight χ′′ signals that exhibit spin glasses behavior. Interestingly, electrospray ionization mass spectrometry (ESI-MS) indicates that the both heptanuclear clusters retain their compositions in acetonitrile solution.

Crystallography and Mass-Spectrometry of Heptanuclear Disk Mn(II) Cluster

(1-methyl-1H-benzo[d]imidazol-2-yl) methanol (Hmbm) reacts with Mn(ClO4)2·6H2O to form heptanuclear disks [Mn7(mbm)12]·2(ClO4) (1) under ambient conditions. The heptanuclear cluster was previously described as a double calix unit with the hydroxides in the middle. The seven Mn(II) ions are essentially coplanar as expected for all edge-sharing octahedra, which can be intituled as a segment of Mg(OH)2 layer of brucite, so it is a symmetric disk. ESI–MS of crystals showed its stability in solution. Time-dependent mass spectrometry (MS) from solutions at different period of the assembly reveal a hierarchical sequence, [MnIII(mbm)2]+ → [MnII2(mbm)3]+ → [MnII4(mbm)6(ClO4)]+ → [MnIIIMnII6(mbm)12(ClO4)2]+.

Solvent-induced structural transformation from heptanuclear to decanuclear [Co-Ln] coordination clusters: trapping of unique counteranion and understanding of aggregation pathways.

Five new cobalt(ii/iii)-lanthanide(iii)-based coordination aggregates, [LnIII3CoII2CoIII2(L1)2(O2CCMe3)8(OH)4(OMe)2(H2O)4]·Ln(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2·2MeOH·2H2O (where Ln = Tb (1), Ho (3), and H2L1 = N-(2-hydroxyethyl)-salicylaldimine), TbIII3CoII3CoIII4(L1)4(O2CCMe3)9(OH)10(H2O) (4) and LnIII3CoII2CoIII5(L1)4(O2CCMe3)10(OH)10 (Ln = Dy (5), Ho (6)) have been synthesized and characterized, including structural analysis via single-crystal X-ray diffraction. The dysprosium analogue (2) of 1 and 3 was previously reported by us. The heptanuclear monocationic clusters in 1 and 3 were formed by placement of seven metal ions (4 Co and 3 Ln) in a vertex shared dicubane structure from the control of two Schiff base anions and crystallized in the presence of in situ generated and literature unknown counter anions Tb(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2- and Ho(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2-. Interesting solvent-induced cluster structure transformation was observed on dissolving the heptanuclear aggregates in MeCN for the formation of decanuclear clusters 4-6. These high nuclearity clusters consist of a vertex shared heptanuclear dicubane part and a curved trinuclear chain linking the two cubic halves. The dicubane unit differs from that of the heptanuclear precursors in the presence of CoII/III at the shared vertex as opposed to LnIII and the absence of OMe- bridges. HRMS (+ve) analysis shed light on the pathway of formation of these heptanuclear molecules, while at the same time revealing a different aggregation process for the decanuclear clusters.

Tuning the Ferrotoroidic Coupling and Magnetic Hysteresis in Double‐Triangle Complexes {Dy3MIIIDy3} via the MIII‐linker

AbstractWe present the syntheses, structures, magnetic data and theoretical analyses for two families of heptanuclear clusters, wherein two staggered dysprosium(III) triangles are linked by various M(III) d‐/p‐block ions. The families differ in the counter‐anion and are of formulae [DyIII6MIII(OH)8(o‐tol)12(MeOH)5(NO3)] ⋅ 4MeOH and [DyIII6MIII(OH)8(o‐tol)12(MeOH)6]Cl ⋅ 6MeOH (M=Cr, Mn, Fe, Co, Al; o‐tol=o‐toluate). We find that variation of the central metal ion M is crucial in tuning the toroidal moments on the triangular units, with diamagnetic M linking ions enhancing the ferrotoroidic coupling. By detailed simulation and analysis of various magnetic measurements, including sub‐kelvin microSquid hysteresis loops, we identified the specific signature of the M linking ions’ modulation of toroidal properties, including the mechanism whereby anisotropic, paramagnetic M ions lead to hysteresis profiles with larger remnant magnetisations and broader coercive fields.

A Heterometallic Three-Dimensional Metal-Organic Framework Bearing an Unprecedented One-Dimensional Branched-Chain Secondary Building Unit.

A heterometallic metal−organic framework (MOF) of [Cd6Ca4(BTB)6(HCOO)2(DEF)2(H2O)12]∙DEF∙xSol (1, H3BTB = benzene-1,3,5-tribenzoic acid; DEF = N,N′-diethylformamide; xSol. = undefined solvates within the pore) was prepared by solvothermal reaction of Cd(NO3)2·4H2O, CaO and H3BTB in a mixed solvent of DEF/H2O/HNO3. The compatibility of these two divalent cations from different blocks of the periodic table results in a solid-state structure consisting of an unusual combination of a discrete V-shaped heptanuclear cluster of [Cd2Ca]2Ca′ and an infinite one-dimensional (1D) chain of [Cd2CaCa′]n that are orthogonally linked via a corner-shared Ca2+ ion (denoted as Ca′), giving rise to an unprecedented branched-chain secondary building unit (SBU). These SBUs propagate via tridentate BTB to yield a three-dimensional (3D) structure featuring a corner-truncated P41 helix in MOF 1. This outcome highlights the unique topologies possible via the combination of carefully chosen s- and d-block metal ions with polydentate ligands.

Hydride-encapsulated bimetallic clusters supported by 1,1-dithiolates.

Two mixed-metal hydride clusters, corresponding to x = 3 and 4, were structurally characterized from a set of atomically precise heptanuclear clusters, CuxAg7-x(H){S2P(OiPr)2}6 (x = 1-6). An interstitial hydride lying at the center of a tricapped tetrahedral cage was located and refined anisotropically by using X-ray data, and its presence acertained by multinuclear NMR spectroscopy and DFT calculations.

Aggregation of heptanuclear [MII7] (M = Co, Ni, Zn) clusters by a Schiff-base ligand derived from o-vanillin: Synthesis, crystal structures and magnetic properties

Three transition metal heptanuclear clusters, [Co7L6(μ3-OCH3)6](ClO4)2·H2O (1), [Ni7L6(μ3-OH)6](ClO4)2·4DMF (2), [Zn7L6(μ3-OCH3)6](ClO4)2 (3), have been obtained using a new Schiff base ligand (HL) derived from o-vanillin and 2-methoxybenzylamine. The structures of 1–3 have been determined based on single crystal X-ray diffraction studies. They have similar wheel structures in which six metal ions locate on the rim with the seventh metal ion in the center. Complex 3 exhibits luminescence in the solid state at room temperature. Variable-temperature DC and AC magnetic studies were carried out on polycrystalline samples of 1 and 2. Compound 1 shows an overall ferromagnetic coupling and absence of SMM behavior despite the observation of out-of-phase susceptibility in external applied field. The analysis of the magnetic data for compound 2 emphasizes the interplay of ferromagnetic interactions between central and peripheral nickel(II) ions (J1 = −11.2 cm−1), and antiferromagnetic interactions between the peripheral nickel(II) ions (J2 = 9.6 cm−1); H = ΣJijSiSj.

Octahedral erbium and ytterbium ion encapsulated in phosphorescent iridium complexes showing field-induced magnetization relaxation

Abstract Four isostructural heptanuclear clusters [LnIr6(ppy)12(bpp)2(bppH)4](CF3SO3)·xH2O (Ir6Ln, Ln = Eu, Tb, Er, Yb) are reported, where the lanthanide ions are six-coordinated by the phosphonate oxygen donors from six [Ir(ppy)2(bpp)] (ppy− = 2-phenylpyridine, bpp2− = 2-pyridylphosphonate) chromophores. All show phosphorescence originating from the IrIII moieties. For compounds Ir6Er and Ir6Yb, field-induced slow magnetization relaxation is also observed, thus providing the first examples of Ir-Er or Ir-Yb complexes showing bifunctional phosphorescence and field-induced single ion magnet behaviors.

Hexanuclear and Heptanuclear Nickel(II) Complexes of with a Non-Schiff-Base Tetradentate Ligand: an Example of Slow Motion Ferromagnetic Phase Transition at Very Low Temperature

Hexanuclear and heptanuclear nickel(II) complexes with N,N′-bis(2-hydroxy-3,5-dimethylbenzyl-1,2-ethanediamine (H2hdde), [Ni6(hdde)3(OH)4(NO3)2(H2O)2]·2dmf (dmf = N,N-dimethylformamide) and [Ni7(hdde)3(OH)6(dmac)3](ClO4)2 (dmac = N,N-dimethylacetamide), were investigated. The latter complex was newly synthesized and the single-crystal X-ray structure analysis revealed a wheel-shaped heptanuclear cluster. These complexes showed a ferromagnetic interaction in the temperature dependence of magnetic susceptibilities. The micro-SQUID data of the former complex did not show SMM property, whereas the AC susceptibility measurements suggested SMM-like behavior and the zero-field-cooled and field-cooled studies showed a ferromagnetic transition near 240 mK for the latter complex.

Tetranuclear MnII/ZnII and Novel Azido‐Bridged Chair‐Shaped Heptanuclear CdII Compounds: The Effect of Metal Ion and Coordination Mode of the Azide Group on the Structure of the Products

We report two tetranuclear compounds [MnL(N3)]4 (1), [Zn4L4(N3)2][Zn(N3)4]·3H2O (2) and a novel heptanuclear cluster [Cd7L6(N3)6](NO3)1.33(N3)0.66·12H2O (3) where L is a hydrazone Schiff base ligand based on pyridine. The ligand acts as a negatively charged tetradentate N3O‐donor ligand and coordinates to the metal centers in the enolic form in 1–3. However, in compound 2, the ligand coordinated to the ZnII ion in the two different coordination modes. Metal centers in 1 and 2, bridged by the organic ligand form tetranuclear metal organic complexes and the N3– anion acts as terminal ligand. In compound 3, N3– acts as bridging ligand to the cadmium(II) centers, and form a rare heptanuclear cluster with an interesting chair conformation. The latter compound is a novel azido‐bridged chair‐shaped heptanuclear CdII cluster that guides the formation of a water hexamer in the solid state. It acts as a robust binding block in the recognition of nitrate. The ability of the water hexamer to bind anions has been analyzed using DFT calculations and several computational tools.

Structures, Magnetic and Thermodynamic Properties of a 3d–4f Mixed Metal Cluster [ErZn6(μ3-O)3(μ3-C2H4NO2)6(H2O)9]6+

A heterometallic 3d–4f complex with hepta-nuclear hexagonal cluster, [ErZn6(μ3-O)3(μ3-C2H4NO2)6(H2O)9]6+ (C2H4NO2 = glycine) was synthesized and characterized. The cluster belongs to hexagonal crystal system. It crystallizes in the P-6 space group. In each cluster, Er3+ ion is in the center of a prism, which is composed of six zinc atoms. Er3+ ion coordinates to nine oxygen atoms. Each glycine ligand chelates to two Zn2+ and one Er3+ ions using a μ3-coordination mode. Fluorescent, thermodynamic and magnetic studies of the cluster were performed. The complex does not show single molecule magnet behavior.

Chiral Silver-Lanthanide Metal-Organic Frameworks Comprised of One-Dimensional Triple Right-Handed Helical Chains Based on [Ln7(μ3-OH)8]13+ Clusters.

Three new isostructural chiral silver-lanthanide heterometal-organic frameworks [Ag3Ln7(μ3-OH)8(bpdc)6(NO3)3(H2O)6](NO3)·2H2O [Ln = Eu (1), Tb (2, Sm (3); H2bpdc = 2,2'-bipyridine-3,3'-dicarboxylic acid] based on heptanuclear lanthanide clusters [Ln7(μ3-OH)8]13+ comprised of one-dimensional triple right-handed helical chains were hydrothermally synthesized. Various means such as UV-vis spectroscopy, IR spectroscopy, elemental analysis, powder X-ray diffraction, and thermogravimetric/differential thermal analysis were used to characterize the compounds, wherein compound 3 was crystallographically characterized. In the structure of compound 3, eight μ3-OH- groups link seven Sm3+ ions, forming a heptanuclear cluster, [Sm7(μ3-OH)8]13+, and the adjacent [Sm7(μ3-OH)8]13+ clusters are linked by the carboxylic groups of bpdc2- ligands, leading to the formation of a one-dimensional triple right-handed helical chain. The adjacent triple right-handed helical chains are further joined together by coordinating the pyridyl N atoms of the bpdc2- ligands with Ag+, resulting in a chiral three-dimensional silver(I)-lanthanide(III) heterometal-organic framework with one-dimensional channels wherein NO3- anions and crystal lattice H2O molecules are trapped. The compounds were studied systematically with respect to their photoluminescence properties and energy-transfer mechanism, and it was found that H2bpdc (the energy level for the triplet states of the ligand H2bpdc is 21505 cm-1) can sensitize Eu3+ luminescence more effectively than Tb3+ and Sm3+ luminescence because of effective energy transfer from bpdc2- to Eu3+ under excitation in compound 1.

Diverse Structures Based on a Heptanuclear Cobalt Cluster with 0D to 3D Metal-Organic Frameworks: Magnetism and Application in Batteries.

Polymetallic complexes with interesting multifunctions have attracted extensive investigation. Synthesized through the use of different cobalt salt anions and solvents, five complexes, namely [CoII4 CoIII3 (H2 L)3 Cl5 (MeOH)] (1), [CoII4 CoIII3 (H2 L)3 (CH3 COO)4 (HCOO)⋅H2 O]n (2), [CoII4 CoIII3 (H2 L)3 (HCOO)4 (NO3 )⋅2H2 O]n (3), [CoII4 CoIII3 (H2 L)3 (bda)(CH3 COO)4 ⋅2H2 O]n (4), and [CoII4 CoIII3 (H2 L)3 (ipa)(HCOO)3 (dmf)⋅H2 O]n (5) (H6 L=bis-tris propane; BDA=biphenyl-4,4'-dicarboxylic acid; IPA=isophthalic acid; DMF=N,N-dimethylformamide), based on the heptanuclear {CoII4 CoIII3 } cluster with structures from 0D to 3D metal-organic frameworks (MOFs) have been solvothermally synthesized. Compound 1 is the first 0D heptanuclear cluster based on H6 L. Compound 2 crystallizes in the chiral space group P21 21 21 and consists of a 1D chiral helical chain. Complex 3 exhibits a 3D network structure. Compound 4 possesses a 1D zigzag-like chain structure. Finally, compound 5 was obtained as a 3D microporous structure. Compounds 1, 3, and 4 display dominant ferrimagnetic interactions whereas compounds 2 and 5 exhibit antiferromagnetic interactions. Moreover, the Co3 O4 prepared by calcining compound 2 presents a reversible capacity of 1122.9 mA h g-1 at 0.2 A g-1 after 100 cycles and an excellent rate capability, which suggests that coordination compounds with a 1D chain structure are outstanding precursors for preparing anode materials for lithium ion batteries.

Simple Access to the Heaviest Alkaline Earth Metal Hydride: A Strongly Reducing Hydrocarbon-Soluble Barium Hydride Cluster.

Reaction of Ba[N(SiMe3 )2 ]2 with PhSiH3 in toluene gave simple access to the unique Ba hydride cluster Ba7 H7 [N(SiMe3 )2 ]7 that can be described as a square pyramid spanned by five Ba2+ ions with two flanking BaH[N(SiMe3 )2 ] units. This heptanuclear cluster is well soluble in aromatic solvents, and the hydride 1 H NMR signals and coupling pattern suggests that the structure is stable in solution. At 95 °C, no coalescence of hydride signals is observed but the cluster slowly decomposes to undefined barium hydride species. The complex Ba7 H7 [N(SiMe3 )2 ]7 is a very strong reducing agent that already at room temperature reacts with Me3 SiCH=CH2 , norbornadiene, and ethylene. The highly reactive alkyl barium intermediates cannot be observed and deprotonate the (Me3 Si)2 N- ion, as confirmed by the crystal structure of Ba14 H12 [N(SiMe3 )2 ]12 [(Me3 Si)(Me2 SiCH2 )N]4 .

Simple Access to the Heaviest Alkaline Earth Metal Hydride: A Strongly Reducing Hydrocarbon‐Soluble Barium Hydride Cluster

AbstractReaction of Ba[N(SiMe3)2]2 with PhSiH3 in toluene gave simple access to the unique Ba hydride cluster Ba7H7[N(SiMe3)2]7 that can be described as a square pyramid spanned by five Ba2+ ions with two flanking BaH[N(SiMe3)2] units. This heptanuclear cluster is well soluble in aromatic solvents, and the hydride 1H NMR signals and coupling pattern suggests that the structure is stable in solution. At 95 °C, no coalescence of hydride signals is observed but the cluster slowly decomposes to undefined barium hydride species. The complex Ba7H7[N(SiMe3)2]7 is a very strong reducing agent that already at room temperature reacts with Me3SiCH=CH2, norbornadiene, and ethylene. The highly reactive alkyl barium intermediates cannot be observed and deprotonate the (Me3Si)2N− ion, as confirmed by the crystal structure of Ba14H12[N(SiMe3)2]12[(Me3Si)(Me2SiCH2)N]4.