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

Pd8(PDip)6: Cubic, Unsaturated, Zerovalent

Atomically precise nanoclusters hold promise for supramolecular assembly and (opto)electronic- as well as magnetic materials. Herein, this work reports that treating palladium(0) precursors with a triphosphirane affords strongly colored Pd8(PDip)6 that is fully characterized by mass spectrometry, heteronuclear and Cross-Polarization Magic-Angle Spinning (CP-MAS) NMR-, infrared (IR), UV-vis, and X-ray photoelectron (XP) spectroscopies, single-crystal X-Ray diffraction (sc-XRD), mass spectrometry, and cyclovoltammetry (CV). This coordinatively unsaturated 104-electron Pd(0) cluster features a cubic Pd8-core, µ4-capping phosphinidene ligands, and is air-stable. Quantum chemical calculations provide insight to the cluster's electronic structure and suggest 5s/4d orbital mixing as well as minor Pd─P covalency. Trapping experiments reveal that cluster growth proceeds via insertion of Pd(0) into the triphosphirane. The unsaturated cluster senses ethylene and binds isocyanides, which triggers the rearrangement to a tetrahedral structure with a reduced frontier orbital energy gap. These experiments demonstrate facile cluster manipulation and highlight non-destructive cluster rearrangement as is required for supramolecular assembly.

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.

Discrete palladium clusters that consist of two mutually bisecting perpendicular planes

The construction of novel molecules with unprecedented alignments of the constituent elements has revolutionized the field of functional materials. The arrangement of two or more planar subunits in a mutually perpendicular fashion is a frequently encountered approach to produce novel functional materials. Previous examples of such materials can be categorized into two well-investigated families: spiro-conjugated and dumbbell-shaped structures, wherein the two planes are aligned orthogonally via a single atom or an axis, respectively. This article describes a third family: reaction of [Pd(CN^tBu)₂]₃ with Sn₃Me₈ or Ge₆Me₁₂ afforded a Pd₇Sn₄ cluster and a Pd₈Ge₆ cluster that consist of two mutually bisecting perpendicular planes. In the Pd₇Sn₄ cluster, the two equivalent Pd₅Sn₂ planes share three palladium atoms that include a dihedral angle of 85.6°.

The construction of Pd₇Sn₄ and Pd₈Ge₆ clusters that consist of two mutually bisecting perpendicular planes was accomplished by the reaction of [Pd(CN^tBu)₂]₃ with Me₃Sn–SnMe₂–SnMe₃ or Ge₆Me₁₂.

From polygons to polyhedra through intermediate structures. A shape measures study of six-atom inorganic rings and clusters

Among the wealth of well-established molecular structures, inorganic rings and clusters present an overwhelming variety of geometries that chemists try to describe with a limited assortment of regular polygons and polyhedra. In the case of six-atom structures we usually employ the hexagon, the pentagonal pyramid, the trigonal prism and the octahedron. More often than not, however, real world structures deviate from those ideal geometries, and we try to cope with non-ideality by adding adjectives such as distorted, twisted, puckered or flattened, additionally nuanced by adverbs such as slightly, significantly or severely. This contribution presents a systematic structural perspective of six-atom groups in molecules by means of a continuous shape measures (CShM) analysis. The shape of a group of N points is defined by all the sets of 3 N Cartesian coordinates that can be generated by rigid translation, rotation, or isotropic scale change. Among all possible arrangements of N points in space, we select as reference shapes the corresponding regular N-vertex polygons and polyhedra, together with univocally defined combinations thereof (e.g., two coplanar or perpendicular edge-sharing squares). The present CShM study allows us to classify most of the structures not only by their closeness to a particular regular shape, but also by quantifying their position along minimal distortion interconversion pathways between two regular shapes.

Nuclearity expansion in Pd clusters triggered by the migration of a phenyl group in cyclooligosilanes

Heptanuclear palladium clusters with six palladium atoms in a planar arrangement were obtained from the reaction of [Pd(CNtBu)2]3 with Ph-substituted cyclotetrasilane or cyclopentasilane via the migration of a phenyl group. The molecular structures of these clusters as well as those of two possible intermediates were determined by single-crystal X-ray diffraction analyses.

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.

A sandwich-type cluster containing Ge@Pd3 planar fragment flanked by aromatic nonagermanide caps

Sandwich-type clusters with the planar fragment containing a heterometallic sheet have remained elusive. In this work, we introduce the [K(2,2,2-crypt)]4{(Ge9)2[η6-Ge(PdPPh3)3]} complex that contains a heterometallic sandwich fragment. The title compound is structurally characterized by means of single-crystal X-ray diffraction, which reveals the presence of an unusual heteroatomic metal planar fragment Ge@Pd3. The planar fragment contains a rare formal zerovalent germanium core and a peculiar bonding mode of sp2-Ge@(PdPPh3)3 trigonal planar structure, whereas the nonagermanide fragments act as capping ligands. The chemical bonding pattern of the planar fragment consists of three 2c-2e Pd-Ge σ-bonds attaching Pd atoms to the core Ge atom, while the binding between the planar fragment and the aromatic Ge9 ligands is provided by six 2c-2e Pd-Ge σ-bonds and two delocalized 4c-2e σ-bonds. The synthesized cluster represents a rare example of a sandwich compound with the heteroatomic metal planar fragment and inorganic aromatic capping ligands.