Ligand Size Research Articles

Applications of a grid-based CYP3A4 Template system to understand the interacting mechanisms of large-size ligands; part 4 of CYP3A4 Template study

Catalytic interactions of CYP3A4 with large-size ligands have been studied on the Template established in our previous studies using polyaromatic hydrocarbon and steroid ligands (DMPK 34: 113–125 and 351–364 2019 and in press 2020). Typical CYP3A4-substrates including erythromycin, cyclosporin A (ca.1200 Da), ivermectin B1a and taxanes were applied successfully and regioselective metabolisms of these ligands were reconstituted faithfully on Template. These results suggest the applicability of CYP3A4 Template throughout broadened sizes of CYP3A4 ligands. Macrolide antibiotics showed distinct degrees of tight sittings in Width-gauge, a tool for accommodation measure. The observed differences were associated with different inhibitory/inactivation potentials of troleandomycin, erythromycin, clarithromycin and azithromycin, suggesting CYP3A4 Template also as a tool for drug-interaction mechanisms. Slight expansion of Template area was made at near Site of oxidation from simulation results of antitumor agent, rilpivirine, in the present study. Ligand entry from left side of Template is also suggested from macrolide interactions. Broadened applicability of the refined CYP3A4 Template were assured with experiments with various large-size ligands.

Constructing Strategies and Applications of Nitrogen-Rich Energetic Metal–Organic Framework Materials

The synthesis of energetic metal–organic frameworks (EMOFs) with one-dimensional, two-dimensional and three-dimensional structures is an effective strategy for developing new-generation high-energy-density and insensitive materials. The basic properties, models, synthetic strategies and applications of EMOF materials with nitrogen-rich energetic groups as ligands are reviewed. In contrast with traditional energetic materials, EMOFs exhibit some interesting characteristics, like tunable structure, diverse pores, high-density, high-detonation heat and so on. The traditional strategies to design EMOF materials with ideal properties are just to change the types and the size of energetic ligands and to select different metal ions. Recently, some new design concepts have come forth to produce more EMOFs materials with excellent properties, by modifying the energetic groups on the ligands and introducing highly energetic anion into skeleton, encapsulating metastable anions, introducing templates and so on. The paper points out that appropriate constructing strategy should be adopted according to the inherent characteristics of different EMOFs, by combining with functional requirements and considering the difficulties and the cost of production. To promote the development and application of EMOF materials, the more accurate and comprehensive synthesis, systematic performance measurement methods, theoretical calculation and structure simulation should be reinforced.

Formation of Fe(III)-phosphonate Coatings on Barium Hexaferrite Nanoplatelets for Porous Nanomagnets.

Amorphous coatings formed with mono-, di-, and tetra-phosphonic acids on barium hexaferrite (BHF) nanoplatelets using various synthesis conditions. The coatings, synthesized in water with di- or tetra-phosphonic acids, were thicker than that could be expected from the ligand size and the surface coverage, as determined by thermogravimetric analysis. Here, we propose a mechanism for coating formation based on direct evidence of the surface dissolution/precipitation of the BHF nanoplatelets. The partial dissolution of the nanoplatelets was observed with atomic-resolution scanning transmission electron microscopy, and the released Fe(III) ions were detected with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy in amorphous coating. The strong chemical interaction between the surface Fe(III) ions with phosphonic ligands induces the dissolution of BHF nanoplatelets and the consequent precipitation of the Fe(III)-phosphonates that assemble into a porous coating. The so-obtained porous nanomagnets are highly responsive to a very weak magnetic field (in the order of Earth’s magnetic field) at room temperature, which is a major advantage over the classic mesoporous nanomaterials and metal–organo-phosphonic frameworks with only a weak magnetic response at a few kelvins. The combination of porosity with the intrinsic magneto-crystalline anisotropy of BHF can be exploited, for example, as sorbents for heavy metals from contaminated water.

The effects of ligand charge, orientation and size on the binding of potential inhibitors for aldehyde dehydrogenase

l-DOPA, used as a therapy for patients with Parkinson’s disease, is transformed into needed dopamine in the brain. This dopamine can then be deactivated via metabolism by a series of enzymes, including aldehyde dehydrogenase (ALDH). The targeted inhibition of the ALDH enzyme may help to prolong l-DOPA therapy. A series of potential inhibitors has been studied viaab initiomodels using a crystal-structure of the ALDH enzyme with an inhibitor bound in its active site (PDB ID: 4WP7). The positions of novel dopaminergic derivatives were optimized in the active site using M062X/6-31G with implicit solvation and relaxed amino-acid side-chains. This work examines different single molecule orientations, as well as double molecule configurations. Various sizes of ligands were also studied. Interaction energies between the ligands and the protein were calculated using M062X with the 6–311 + G* basis set. Some potential inhibitors show promising results such as the LP and CAM series.

Reaction Rate Inside the Cavity of [Ga4 L6 ]12- Supramolecular Metallocage is Regulated by the Encapsulated Solvent.

In the present study the dependence of the reaction rate of carbon-carbon reductive elimination from R3 PAu(MeOH)(CH3 )2 (R=Me, Et) complexes inside [Ga4 L6 ]12- metallocage on the nature of the phosphine ligand is investigated by computational means. The reductive elimination mechanism is analyzed in methanol solution and inside the metallocage. Classical molecular dynamics simulations reveal that the smaller the gold complex (which depends on the phosphine ligand size) the larger the number of solvent molecules encapsulated. The size of the phosphine ligands defines the space that is left available inside the cavity that can be occupied by solvent molecules. The Gibbs energy barriers calculated at DFT level, in excellent agreement with experiment both in solution and in the metallocage, show that the presence/absence of explicit solvent molecules inside the cavity significantly modifies the reaction rate.

Solution NMR Studies of CYP121 of Mycobacterium tuberculosis; Evidence that Ligand Binding is Bi‐modal

Mycobacterium tuberculosis (Mtb) is the causative pathogen in the development of tuberculosis (TB). The rise of multi‐drug resistant forms of TB, combined with the fact that one third of the world’s population are carriers of latent TB, underscores the need for the development of novel anti‐TB agents. A current drug target is the cytochrome P450 (CYP) 121 of Mtb; an essential enzyme that mediates an unusual phenol coupling reaction of the dipeptide di‐cyclotyrosine (cYY). Our current understanding of atomic level active site/inhibitor interactions in CYP121 stems primarily from co‐crystallization of drug fragments or cYY with the enzyme. However, these studies result in protein structures that reflect the same unchanging conformation, thus resulting in a gap in our understanding of dynamic active site/ligand interactions that would otherwise help inform specificity in the design of novel CYP121 inhibitors.In this preliminary work, we’ve begun to address this gap by adapting CYP121 for analysis by solution NMR. The enzyme produces a well‐dispersed, resolvable 1H‐15N HSQC spectrum. We have acquired 2D spectra of the enzyme while bound to a variety of azoles representing a range of ligand sizes and chemistry. We report that, while ligands with a similar overall structure (econazole and miconazole) produce similar perturbations of the NMR spectra, other ligands with distinct overall structures (ketoconazole and fluconazole) produce chemical shift perturbations that are unexpectedly similar to each other, yet can be categorized separately from other ligand‐induced changes. These preliminary studies suggest that ligand binding in CYP121 is partially bi‐modal, indicative of a structure that retains a semi‐rigid backbone in solution. This work lays the foundation for understanding CYP121 dynamics that will be a critical component of future drug design of novel anti‐TB agents.Support or Funding InformationResearch supported by start‐up funds at SUNY BuffaloA backbone amide resonance of CYP121 in response to azole bindingFigure 1

Multi trace element profiling in pathogenic and non-pathogenic fungi

Maintaining appropriate levels of trace elements during infection of a host is essential for microbial pathogenicity. Here we compared the uptake of 10 trace elements from 3 commonly-used laboratory media by 3 pathogens, Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus, and a model yeast, Saccharomyces cerevisiae. The trace element composition of the yeasts, C. albicans, C. neoformans and S. cerevisiae, grown in rich (YPD) medium, differed primarily in P, S, Fe, Zn and Co. Speciation analysis of the intracellular fraction, which indicates the size of the organic ligands with which trace elements are complexed, showed that the ligands for S were similar in the three fungi but there were significant differences in binding partners for Fe and Zn between C. neoformans and S.cerevisiae. The profile for Cu varied across the 3 yeast species. In a comparison of C. albicans and A. fumigatus hyphae, the former showed higher Fe, Cu, Zn and Mn, while A. fumigatus contained higher P, S Ca and Mo. Washing C. albicans cells with the cell-impermeable chelator, EGTA, depleted 50–90 % of cellular Ca, suggesting that a large proportion of this cation is stored in the cell wall. Treatment with the cell wall stressor, Calcofluor White (CFW), alone had little effect on the elemental profile whilst combined Ca + CFW stress resulted in high cellular Cu and very high Ca. Together our data enhance our understanding of trace element uptake by pathogenic fungi and provide evidence for the cell wall as an important storage organelle for Ca.

Heteroleptic NiII complexes: Synthesis, structural characterization, computational studies and amoebicidal activity evaluation

In this work, we present the synthesis, characterization, electrochemical studies, DFT calculations, and in vitro amoebicidal effect of seven new heteroleptic NiII coordination compounds. The crystal structures of [H2(pdto)](NO3)2 and [Ni(pdto)(NO3)]PF6 are presented, pdto = 2,2′-[1,2-ethanediylbis-(sulfanediyl-2,1-ethanediyl)]dipyridine. The rest of the compounds have general formulae: [Ni(pdto)(NN)](PF6) where N-N = 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (44dmbpy), 5,5′-dimethyl-2,2′-bipyridine (55dmbpy), 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (47dmphen) and 5,6-dimethyl-1,10-phenanthroline (56dmphen). The size of NN ligand and its substituents modulate the compound electronic features and influence their antiproliferative efficiency against Entamoeba histolytica. 56dmphen derivative, shows the biggest molar volume and presents a powerful amoebicidal activity (IC50 = 1.2 μM), being seven times more effective than the first-line drug for human amoebiasis metronidazole. Also, increases the reactive oxygen species concentration within the trophozoites. This could be the trigger of the E. histolytica growth inhibition. The antiparasitic effect is described using NiII electron density, molar volume, estimated by DFT, as well as the experimental redox potential and diffusion coefficients. In general, amoebicidal efficiency is directly proportional to the increment of the molar volume and decreases when the redox potential becomes more positive.

Immunosuppressive Siglec-E ligands on mouse aorta are up-regulated by LPS via NF-κB pathway

AimsSiglec-E, the mouse ortholog of human Siglec-9, is an immunosuppressive cell surface receptor. Both Siglec-E and Siglec-9 are primarily found on neutrophils, macrophages, and monocytes. When Siglec-E binds to sialoglycan ligands in its extracellular environment, it halts the immune cells’ inflammatory responses. In the present study, we aimed to investigate expression, mechanisms of action and regulation of Siglec-E ligands during vascular inflammation induced by E. coli lipopolysaccharides (LPS) in mouse aorta. MethodsThe distribution, molecular size and glycoprotein class of Siglec-E ligands on mouse aorta were determined, and the protein carrier of the ligands was identified. In vivo, the expression of Siglec-E ligands was detected after LPS treatment, with or without NF-κB inhibitor administration. In vitro, cultured primary mouse aortic endothelial cells (MAECs) were used to study changes in expression of Siglec-E ligands induced by LPS with or without NF-κB inhibitors. MAECs induced by LPS were co-cultured with macrophages and the effect of increased expression of Siglec-E ligands analyzed. ResultsSiglec-E ligands are O-linked sialoglycoproteins with molecular weights of 70−300 kDa and are distributed broadly on mouse aorta as well as on MAECs in vitro. In vivo, the expression of Siglec-E ligands was increased in mice aortas in response to LPS treatment in an NF-κB signaling pathway dependent manner. In MAECs, the expression of Siglec-E ligands was also increased by LPS via an NF-κB signaling pathway. Deleted in malignant brain tumors-1 was identified to be one of multiple protein carriers of Siglec-E ligands, and glycans of ligands involved in MAECs induced by LPS. Notably, co-incubation of macrophages with LPS-treated MAECs induced macrophage apoptosis and decreased macrophage phagocytosis, effects that were completely reversed by blocking Siglec-E binding to Siglec-E ligands. ConclusionsThese data demonstrated that Siglec-E ligands were highly expressed in response to LPS-induced vascular inflammation and inhibited the immune response of macrophages, which may be a therapeutic strategy to interfere with vascular inflammation.

Stereoelectronic Properties of 1,2,4-Triazole-Derived N-heterocyclic Carbenes - A Theoretical Study

Stereoelectronic Properties of 1,2,4-Triazole-Derived N-heterocyclic Carbenes - A Theoretical Study

Investigating Polymer Transformation during the Encapsulation of Metal Nanoparticles by Polystyrene-b-poly(acrylic acid) in Colloids

The colloidal self-assembly method holds great potential for large-scale synthesis at low expense of energy as compared to methods that assemble molecules by manipulating building blocks one after another. The development of the colloidal method, however, requires careful and intelligent design of the single building blocks as numerous degrees of freedom like isotropic nanoparticles (NPs) generally form highly repetitive, lattice-like structures or random aggregates upon self-assembly because of their identical surfaces throughout. Specifically, it is an interesting direction that if one can precisely control the localization of surface functionalities (i.e., ligands or polymer shells) on the NPs, a plethora of self-assembled structures (e.g., chains, sheets, rings, twisted, and even staircase structures) would be possible. Despite numerous simulations and modeling for this type of NPs, just a handful literature studies reported the controlling synthesis of metal-polymer patchy NPs through polymer shell shrinking/transformation in colloids. However, there are no detailed control experiments showing the mechanism of this polymer shell shrinking or transformation phenomenon. With the absence of a fundamental understanding of the driving forces and interactions between metal NP surface ligands and the hydrophobic polymer shell domain, simple and efficient design and synthesis of unique metal-polymer hybrid nanostructures are still obscure. Here, we report a detailed mechanistic study on the polymer shell transformation by using different types of surface ligands in encapsulation of metal NPs by polymer shells. The polymer shell transformation dynamic is studied after postheating treatment. The polymer shell transformation/shrinking on the metal NP surface depends on its surface ligand size being applied in the encapsulation step (polymer-ligand hydrophobic interaction effect). Longer-chain ligands provide stronger interactions between NPs and the hydrophobic domain of the polymer shell, which inhibits the polymer shell transformation. In contrast, short-chain ligands lead to weaker interactions, which assist in the polymer shell transformation. By understanding the underlying mechanisms, many new types of NPs, such as metal-polymer core-shell NPs, metal-polymer Janus NPs, silica-metal-polymer hybrid NPs, and silica-metal-polymer flower-like NPs have been synthesized for the first time. A new bottom-up platform for the synthesis of anisotropic NPs with the ability to control the patches in a precise manner has been created, which will benefit both nanotechnology (such as self-assembly in the nanoscale) and applications such as selective detection of the underlying ligands on the metal surface by using a surface-enhanced Raman spectrum study.

Enthalpically-driven ligand recognition and cavity solvation of bovine odorant binding protein

Lipocalins are a widely distributed family of extracellular proteins typically involved in the transport of small hydrophobic molecules. To gain new insights into the molecular basis that governs ligand recognition by this ancient protein family, the binding properties of the domain-swapped dimer bovine odorant binding protein (bOBP) and its monomeric mutant bOBP121G+ were characterized using calorimetric techniques and molecular dynamics simulations. Thermal unfolding profiles revealed that the isolated bOBP subunits behave as a cooperative folding unit. In addition, bOBP and bOBP121G+ exhibited similar ligand binding properties, characterized by a non-classical hydrophobic effect signature. The energetic differences in the binding of bOBP to 1-hexen-3-ol and the physiological ligand 1-octen-3-ol were strikingly larger than those observed for the interaction of other lipocalins with congeneric ligands. MD simulations revealed that the recurrent opening of transient pores in the submicrosecond timescale allows a profuse exchange of water molecules between the protein interior and the surrounding solvent. This picture contrasts with other lipocalins whose ligand-free binding cavities are devoid of solvent molecules. Furthermore, the simulations indicated that internal water molecules solvate the protein cavity suboptimally, forming fewer hydrogen bonds and having lower density and higher potential energy than bulk water molecules. Upon ligand occupation, water molecules were displaced from the binding cavity in an amount that depended on the ligand size. Taken together, calorimetric and MD-simulation results are consistent with a significant contribution of cavity desolvation to the enthalpically-driven interaction of bOBP with its hydrophobic ligands.

Rationalization of the Superior Anticancer Activity of Phenanthriplatin: An In-Depth Computational Exploration.

In the effort to overcome issues of toxicity and resistance inherent to treatment by the approved platinum anticancer agents, a large number of cisplatin variants continues today to be prepared and tested. One of the applied strategies is to use monofunctional platinum complexes that, unlike traditional bifunctional compounds, are able to form only a single covalent bond with nuclear DNA. Chirality, aquation reaction, interaction with guanine and N-acetyl methionine as well as, intercalation into, binding to and distortion of DNA have been investigated by using both quantum mechanical DFT and molecular dynamics computations aiming at contributing to the elucidation of the molecular mechanism underlying the significantly enhanced spectrum of activity of the monofunctional PtII drug phenanthriplatin. Analogous calculations have been performed in parallel for other two less potent monofunctional PtII drugs, pyriplatin and enpyriplatin, which show very different cytotoxic effects.

Anticancer activity and DNA interaction of ruthenium acetate clusters bearing azanaphthalene ancillary ligands

Six triruthenium complexes (1–6) ([Ru3O(CH3COO)6(L)3]PF6, L = quinazoline (qui) (complex 1), 5-nitroisoquinoline (5-nitroiq) (complex 2), 5-bromoisoquinoline (5-briq) (complex 3), isoquinoline (iq) (complex 4), 5-aminoisoquinoline (5-amiq) (complex 5), and 5,6,7,8-tetrahydroisoquinoline (thiq) (complex 6)) have been studied regarding their anti-cancer activity (B16F10 and A549 cells) and their interactions with fish sperm DNA (fs-DNA). The crystallographic data of complex 4 show the typical triangular geometry, where the three isoquinoline ligands display different degrees of co-planarity with the [Ru3O] unit. In the range of 2 to 200 μM, these complexes make B16F10 cells less viable. The overall cytotoxicity order is complex 4 > complex 6 > complex 2 > complex 5 > complex 1. The two first complexes have IC50 of 10 and 50 μM, respectively, being less toxic to L929 non-tumoral cells. The complexes can displace ethidium bromide (EB) from DNA, but the intercalation constant values (Kapp ~105 M−1) are low due to the smaller size of the azanaphtalene ligands as compared to classic intercalating molecules. Complex 5 provides the highest constants in both the EB displacement (Kapp = 12.5 × 105 M−1) and direct spectrophotometric titration with fs-DNA (Kb = 6.3 × 104 M−1) assays, possibly because its amino group can assist interaction with DNA through hydrogen bonds. Hypochromism of complexes IC band was observed (T = 310 K), suggesting hydrophobic contributions. Low values of Kapp and circular dichroism spectra for DNA-compound 6 mixtures, suggest semi-intercalative and major groove binding interaction modes. Compared to cisplatin, incubation of complexes 1–6 with plasmid pUC19 shows no DNA cleavage. Results for the interaction with DNA do not correlate with cytotoxicity, which suggests that DNA is not the pharmacological target of this class of compounds.

Modification of Aβ Peptide Aggregation via Covalent Binding of a Series of Ru(III) Complexes.

Alzheimer's disease (AD) is the most common form of dementia, leading to loss of cognition, and eventually death. The disease is characterized by the formation of extracellular aggregates of the amyloid-beta (Aβ) peptide and neurofibrillary tangles of tau protein inside cells, and oxidative stress. In this study, we investigate a series of Ru(III) complexes (Ru-N) derived from NAMI-A in which the imidazole ligand has been substituted for pyridine derivatives, as potential therapeutics for AD. The ability of the Ru-N series to bind to Aβ was evaluated by NMR and ESI-MS, and their influence on the Aβ peptide aggregation process was investigated via electrophoresis gel/western blot, TEM, turbidity, and Bradford assays. The complexes were shown to bind covalently to the Aβ peptide, likely via a His residue. Upon binding, the complexes promote the formation of soluble high molecular weight aggregates, in comparison to peptide precipitation for peptide alone. In addition, TEM analysis supports both amorphous and fibrillar aggregate morphology for Ru-N treatments, while only large amorphous aggregates are observed for peptide alone. Overall, our results show that the Ru-N complexes modulate Aβ peptide aggregation, however, the change in the size of the pyridine ligand does not substantially alter the Aβ aggregation process.

Theoretical Study of the Thorium Structural in Solution by EXAFS Techniques

Thorium with symbol Th is radioactive metal which emits the alpha rays. This metal can be founded in different forms and can cause the negatives impacts on human health and environment. This is the reason which explains the importance to know the structure of this metal in different forms including the structure of hydrated Thorium. Structural information helps to understand and assess peculiarities this ion in different natural and technological processes taking place in aqueous solutions. The most and efficacy technique to know about distances between atoms and coordination numbers is EXAFS (extended X Ray Absorption Fine Structure) technique because it permits to know these above informations. My project research is was to determine the structure of hydrated, solvated Thorium ion in metal ions. For my research, I preferred to use the EXAFS method to study the structure of the hydrated Th ion and to determine the Th-O bond distance, and from that estimate the coordination number. Th-O distance in the case of hydrated Thorium appeared to be 2.44 Å which corresponds to 9-coordination, as also found in the solids. The Th-O bond distance in solvated plutonium is ca. 2.41 Å, which corresponds to eightcoordination. These informations have shown me that for Thorium ligand size and coordination number are correlated. In case of Thorium hydrated studies, I saw that shown don’t precipitate at the law concentration. As conclusion, when pH is in range, centrifugation is possible and thorium is in monomeric form, but for pH above 4 Thorium is restrained and centrifuging shown that Thorium is in non-ionic form.

Synthesis of the Cyclic Group 13 Phosphinidenides [(NHC)PMCl2]2 (NHC = SIMes, SIDipp; M = Al, Ga)

The N‐heterocyclic carbene stabilized phosphinidenides (SIMes)PK [SIMes = 1,3‐bis(2,4,6‐trimethylphenyl)imidazolidine‐2‐ylidene] and (SIDipp)PK [SIDipp = 1,3‐bis(2,6‐diisopropylphenyl)imidazolidine‐2‐ylidene] were used as precursors in salt elimination reactions with MCl3 (M = Al, Ga) in order to obtain new group 13 phosphinidenide compounds. The new compounds [(NHC)PMCl2]2 (NHC = SIMes, SIDipp; M = Al, Ga) exhibit dimerization in solid state as well as in solution and show different shapes of the central M2P2 cycle (butterfly or nearly square planar conformation) in solid state, depending on the size of the NHC ligand bound to the phosphorus atom.

Geometrical and Electronic Structure, Stability, and Optical Absorption Spectra Comparisons between Thiolate- and Chloride-Stabilized Gold Nanoclusters.

Thiolate-stabilized gold nanoclusters have drawn significant attention for their extraordinary properties and their applications in many fields such as catalysis, sensing, biomedicine, etc. However, due to the size, complexity, and conformational flexibility of thiolate ligands, accurate structure prediction can be a challenge using computational approaches. Substitution of thiolate ligands with chloride ligands provides a possible alternative. In this work, the stabilities of a series of gold thiolate and chloride clusters with 1:1 stoichiometry (AunLn; L = SH, Cl; n = 2-9) and the analogs of some experimentally observed gold nanoclusters (AunLm; L = SH, Cl; n = 18-133) are examined, and binding energies, HOMO-LUMO gaps, and absorption spectra are determined using density functional theory (DFT). We observed that the optimized geometries of gold nanoclusters for both types of ligands converged to the same local minimum structure as the experimentally observed structures. The average binding energy per gold atom in gold clusters converges after Au4L4. The binding energies of chloride-stabilized gold clusters and nanoclusters average 87.5% and 95.7% of the binding energies of thiolate-stabilized systems for the clusters and nanoclusters, respectively. Typically, thiolates are found to be more stable than the chlorides. However, higher HOMO-LUMO gaps in Au2Cl2, Au38Cl24, and Au102Cl44 compared to their thiolate analogs suggest systems of particular interest for investigating the possible existence of chloride-based gold nanoclusters. Absorption spectra are very similar regardless of the ligand used. This study also demonstrates that in theoretical studies on large nanoclusters, complex thiolate ligands can be replaced by Cl ligands to predict structural and electronic properties with reasonable accuracy and reduced computational effort.

Exceeding Metal Capacity in Sandwich Complexes: Ligand-Unsupported Docking of Extra Metal Moieties at Edges of a Metal Sheet Sandwich Complex.

The ligand-unsupported accommodation of extra metal moieties in a sandwich complex is reported. Although it has been considered that the metal-capacity of a metal sheet sandwich complex is strictly limited by the size of cyclic unsaturated hydrocarbon ligands, the M-M edge bonds in a metal sheet sandwich complex provide a ligand-unsupported docking site for extra metal moieties, allowing expansion of metal-capacity in sandwich complexes. The metal sheet sandwich complex [Pd4 (μ4 -C8 H8 )(μ4 -C9 H9 )]+ , in which the ligand-based metal capacity is full in terms of the usage of all C=C moieties of the smaller carbocyclic ligand C8 H8 in coordination, can accommodate extra M0 {P(OPh)3 }2 (M=Pd, Pt) moieties without coordinative assistance by either the C9 H9 or the C8 H8 ligand.

Exceeding Metal Capacity in Sandwich Complexes: Ligand‐Unsupported Docking of Extra Metal Moieties at Edges of a Metal Sheet Sandwich Complex

AbstractThe ligand‐unsupported accommodation of extra metal moieties in a sandwich complex is reported. Although it has been considered that the metal‐capacity of a metal sheet sandwich complex is strictly limited by the size of cyclic unsaturated hydrocarbon ligands, the M−M edge bonds in a metal sheet sandwich complex provide a ligand‐unsupported docking site for extra metal moieties, allowing expansion of metal‐capacity in sandwich complexes. The metal sheet sandwich complex [Pd4(μ4‐C8H8)(μ4‐C9H9)]+, in which the ligand‐based metal capacity is full in terms of the usage of all C=C moieties of the smaller carbocyclic ligand C8H8 in coordination, can accommodate extra M0{P(OPh)3}2 (M=Pd, Pt) moieties without coordinative assistance by either the C9H9 or the C8H8 ligand.