Palladium cluster complex [Pd13(μ4-C7H7)6]2+ (C7H7 = tropylium) with an fcc-close-packed cuboctahedral Pd13 core and isomers: theoretical insight into ligand-control of the Pd13 core structure

One of the challenging targets in today's chemistry is size-, shape- and metal-atom packing-controlled synthesis of nano-scale transition metal cluster complexes because key factors governing these features have been elusive. Here, we present a DFT study on a recently synthesized palladium cluster complex [Pd13(μ4-C7H7)6]2+ (named Cubo-μ4; C7H7 = tropylium) with an fcc-close-packed cuboctahedral Pd13 core and possible isomers. The stability decreases in the order Cubo-μ4 > [Pd13(μ3-C7H7)3(μ4-C7H7)3]2+ with an hcp-close-packed anticuboctahedral Pd13 core (Anti-μ3,4) > [Pd13(μ3-C7H7)6]2+ with a non-close packed icosahedral Pd13 core (Ih-μ3) > [Pd13(μ4-C7H7)6]2+ with an anticuboctahedral Pd13 core (Anti-μ4) > [Pd13(μ3-C7H7)6]2+ with a cuboctahedral Pd13 core (Cubo-μ3). This ordering disagrees with the stability of the Pd13 core. The key factor governing the stability and metal-atom packing manner of these Pd13 cluster complexes is not the stability of the Pd13 core but the interaction energy between the Pd13 core and the [(C7H7)6]2+ ligand shell. The interaction energy is mainly determined by the charge-transfer from the Pd13 core to the [(C7H7)6]2+ ligand shell and the coordination mode of the C7H7 ligand (μ3- vs. μ4-coordination bond). In the μ4-coordination, all seven C atoms of the C7H7 ligand interact with four Pd atoms of the Pd4 plane using two CC double bonds and one π-allyl moiety. On the other hand, in the μ3-coordination, one or two C atoms of C7H7 cannot form bonding interaction with the Pd atom of the Pd3 plane. Thus, the use of appropriate capping ligands is one of the key points in the synthesis of nano-scale metal cluster complexes.

Di- and trinuclear sandwich complexes of a cross-conjugated fulvene

We report di- and trinuclear palladium sandwich complexes of cross-π-conjugated fulvenes. Structural and theoretical analysis revealed that a fulvene sandwich framework holds a metal-metal bonded moiety, where the dinuclear and trinuclear bonds feature strong donation and back-donation, respectively. The trinuclear fulvene sandwich complex undergoes a unique reversible extrusion of a Pd atom from inside to outside the sandwich framework.

Formation of sandwich and multidecker complexes between O2 and alkali/alkaline earth metals: A DFT study

Abstract: Feasibility of formation of sandwich and multidecker complexes between O2 molecules and alkali/alkaline earth metal has been analyzed in the light of density functional theory (DFT). High value of...

Imidazolium salts and [Pt(cod)2]: from NHC hydrido complexes to the unprecedented olefinic tetrahedral cluster [Pt4(μ-H)(cod)4]BF4

Whereas the bis(imine)imidazolium salt 1·Cl is a potential precursor to a N^imineC^NHCN^imine pincer-type ligand, it reacted with [Pt(cod)₂] to give the Pt^II NHC hydrido complex 3, in which chloride coordination and C^NHCN^imine chelation is preferred over pincer formation. Unexpectedly, reaction of 1·BF₄ with [Pt(cod)₂] afforded the unprecedented, 56 CVE tetrahedral cluster [Pt₄(μ-H)(cod)₄]BF₄ (7), which was fully characterized. Imidazolium salts are ubiquitous sources of the much studied NHC ligands and not expected to lead to the formation of metal clusters.

Selective dimerization of a trinuclear mixed-metal sandwich complex: construction of an axially chiral metal skeleton

Certain metal sandwich complexes undergo dimerization through metal-metal bond formation. Here, we found that a reductive dimerization of mixed-metal Pd₂Pt or PdPt₂ sandwich complexes proceeds through selective Pt-Pt bond formation. A restricted rotation at the Pt-Pt bond of the PdPt₂ dimer gave a unique axially chiral structure derived from a heterometal arrangement in a mixed-metal cluster.

Heterometallic d8 -d10 Coupling of Rh(I) and M(0) (M=Pd, Pt) in a Sandwich Framework of π-Conjugated Ligands

A heterometallic M-M' bond formation is a key to construct atomically precise bimetallic clusters and materials. However, it is sometimes not straightforward to construct a heterometallic M-M' bond through conventional methods including redox condensation. Here, we found that a sandwich framework of π-conjugated unsaturated hydrocarbon ligands provides a unique coordination environment that facilitates unusual coupling of d⁸ Rh^I and d¹⁰ M⁰ (M=Pd, Pt). The molecular orbital analysis showed that the electron-accepting ability of the sandwich framework through back-donation allows the formation of a dσ-type Rh-Pd bond in a (d-d)¹⁸ electron system.

Multinuclear Ag Clusters Sandwiched by Pt Complex Units: Fluxional Behavior and Chiral-at-Cluster Photoluminescence

Multinuclear Ag clusters sandwiched by Pt complex units were synthesized and characterized by single crystal X-ray diffraction and NMR studies. The sandwich-shaped multinuclear Ag complexes showed two different types of fluxional behavior in solution: rapid slippage of Pt complex units on the Ag₃ core and a reversible demetalation-metalation reaction by the treatment with Cl anion and Ag ion, respectively. The Ag₂ complex obtained by demetalation reaction from the Ag₃ complex displayed U to Z isomerization. These multinuclear Ag complexes showed strong photoluminescence whose properties depended on the existence of Pt→Ag dative bonds. The Ag₃ complex, identified to be "chiral-at-cluster", was optically resolved by the formation of a diastereomeric salt with a chiral anion. The enantiomers show circular dichroism (CD) and circularly polarized luminescence (CPL) properties which is unprecedented for compounds based on a chiral sandwich structure. Theoretical calculations allow to understand their structural features and photophysical properties.

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.

Three-Dimensional Sandwich Nanocubes Composed of 13-Atom Palladium Core and Hexakis-Carbocycle Shell

Coordination of cyclic unsaturated hydrocarbons to transition metal generally gives bis-ligated sandwich complexes, which are a fundamental class of organometallic compounds. This sandwich structure may be extended to a higher-order three-dimensional one when more than two carbocyclic ligands surround an agglomerate of many transition metal atoms. Here, we report synthesis of three-dimensional sandwich nanocube compounds containing a close-packed transition metal cluster core. Reduction of a [Pd₃(μ₃-C₇H₇)₂]²⁺ with tetraarylborate under neat conditions afforded [Pd₁₃(μ₄-C₇H₇)₆]²⁺ containing a cuboctahedral Pd₁₃ core with an octahedral ligand-shell.

On the formation of sandwich and multidecker complexes via π⋯π interaction: a DFT study

Sandwich and multidecker complexes via organic π–inorganic π interaction.

B-Hb⋯π interactions in benzene–borazine sandwich and multidecker complexes: a DFT study

Multidecker complexes of benzene/borazine can be formed through B-H_b⋯π interactions.

A niobium-necked cluster [As3Nb(As3Sn3)]3− with aromatic Sn32−

A new Zintl cluster [As₃Nb(As₃Sn₃)]³⁻ was synthesized and characterized, in which an As₃ triangle and a bowl-type As₃Sn₃ ligand are bridged by a niobium atom. The Sn₃ ring is found to have σ-aromaticity featured by a delocalized Sn–Sn–Sn σ orbital.

A mechanistic insight into metal-cluster π-envelopment: a dual binding mode involving bent and planar ligand-conformers

We report a stepwise mechanism of the π-envelopment of a Pd₄ chain cluster. Bent- and planar binding modes of π-conjugated unsaturated hydrocarbon ligands are involved in the π-envelopment process.

Theoretical studies on the bonding and electron structures of a [Au3Sb6]3− complex and its oligomers

Theoretical studies of an all-metal [Sb₃Au₃Sb₃]³⁻ sandwich complex and its congeners [X₃M₃X₃]³⁻ (M = Cu, Ag, Au, Rg; X = N, P, As, Sb, Bi, Uup) as well as [Sb₃(Au₃Sb₃)_n]³⁻ (n = 1–4) oligomers indicate the possible existence of other [A_pM_pA_p]^x− sandwich compounds and oligomers.

Unique cation–cyclohexane interactions in tri- and hexa-fluorocyclohexane multidecker complexes in the gas phase: a DFT study

The formation of stable sandwich and multidecker complexes through electrostatic interaction in tri- and hexa-fluorocyclohexane has been analyzed in the light of density functional theory.

On the nature of chemical bonding in the all-metal aromatic [Sb3Au3Sb3]3− sandwich complex

All-metal aromatic sandwich [Sb₃Au₃Sb₃]³⁻ is held together via three 3c–2e Sb–Au–Sb σ bonds, due to the collective contributions from some 17 molecular orbitals.

Structures and magnetism of multinuclear vanadium-pentacene sandwich clusters and their 1D molecular wires

Two types of multinuclear sandwich clusters, (V(3))(n)Pen(n+1), (V(4))(n)Pen(n+1) (Pen = Pentacene; n = 1, 2), and their corresponding infinite one-dimensional (1D) molecular wires ([V(3)Pen](∞), [V(4)Pen](∞)) are investigated theoretically, especially on their magnetic coupling mechanism. These sandwich clusters and molecular wires are found to be of high stability and exhibit intriguing magnetic properties. The intra-layered V atoms in (V(3))(n)Pen(n+1) clusters prefer antiferromagnetic (AFM) coupling, while they can be either ferromagnetic (FM) or AFM coupling in (V(4))(n)Pen(n+1) depending on the intra-layered V-V distances via direct exchange or superexchange mechanism. The inter-layered V atoms favor FM coupling in (V(3))(2)Pen(3), whereas they are AFM coupled in (V(4))(2)Pen(3). Such magnetic behaviors are the consequence of the competition between direct exchange and superexchange interactions among inter-layered V atoms. In contrast, the 1D molecular wires, [V(3)Pen](∞) and [V(4)Pen](∞), appear to be FM metallic with ultra high magnetic moments of 6.8 and 4.0 μ(B) per unit cell respectively, suggesting that they can be served as good candidates for molecular magnets.

Selective construction of Pd2Pt and PdPt2 triangles in a sandwich framework: carbocyclic ligands as scaffolds for a mixed-metal system

Sandwich time! The mixed-metal triangular-trinuclear sandwich complexes of Pd(2)Pt and PdPt(2) were selectively synthesized. The Pd(2)Pt and PdPt(2) triangles in a cycloheptatrienyl sandwich framework were identified by (31)P NMR analyses of the tris-triphenylphosphine complexes (see scheme).

First structural evidence for multiple alkali metals between sandwich decks in a metallocene

A tetralithio salt (1) derived by treating 1,4-bis(trimethylsilyl)-cyclooctatriene with (n)BuLi serves as the first structural evidence for a multi-alkali metallocene. Single-crystal XRD confirms two Li(+) each asymmetrically bind to η(3) and η(4) between two COT'' rings and two Li(+) terminally bind to η(3). Solid-state NMR studies confirm the presence of two distinct lithium ion sites while the solution NMR studies suggest the formation of an (COT'' dianion) ion-pair in solution. Further treating of the tetralithio salt with NaCl leads to linear sodium polymeric chains. Therefore, simply changing the ionic radius changes the molecular structure.