Embryonic brass: pseudo two electron Cu/Zn clusters.

The isoelectronic M7 clusters [Cu3Zn4](Cp*)5 (1) and {[Cu2Zn5](Cp*)5}+ (2) are described. While 1 can be isolated only as a minor side product from the reaction of Cu(CH3CO2) with equimolar amounts of [Zn2Cp*2] with the trigonal cluster [CuZn2](Cp*)3 as the major product, 2 is available in acceptable yields from the reaction of [CuZn2](Cp*)3 with the Cp*Zn2-transfer-reagent [Cp*Zn2(Et2O)3][BAr4 F]. The trigonal bipyramidal Cu/Zn-clusters exhibit exceptional bonding situations: with formally only one skeleton electron pair they can be regarded as highly electron deficient. However, a detailed DFT analysis reveals that the cluster bonding is supported by 3d orbital contributions of the trigonal metal base unit. The data contribute to the development of an advanced tool-box for synthesis of Hume-Rothery intermetallic (e.g. brass) inspired clusters.

Linker functionalisation triggers an alternative 3D-topology for Zn-isophthalate-4,4'-bipyridine frameworks.

A series of four Zn2+ metal-organic frameworks containing functionalised isophthalate linkers and 4,4'-bipyridine pillars have been prepared and characterised. Isophthalates which contain -OC3H2n+1 alkoxy side chains (with n = 1, 2 or 3) form frameworks with a 3D pillared-layer topology instead of the typical 2D layer topology of the renowned coordination polymers with an interdigitated structure (CIDs), which is found for shorter -OC2H5 side chains. The gas adsorption properties of the materials were analysed using N2, CO2 and O2 adsorption measurements at low temperatures.

Atom-Precise Organometallic Zinc Clusters.

The bottom-up synthesis of organometallic zinc clusters is described. The cation {[Zn10](Cp*)6 Me}(+) (1) is obtained by reacting [Zn2 Cp*2] with [FeCp2][BAr4 (F)] in the presence of ZnMe2. In the presence of suitable ligands, the high reactivity of 1 enables the controlled abstraction of single Zn units, providing access to the lower-nuclearity clusters {[Zn9 ](Cp*)6} (2) and {[Zn8 ](Cp*)5 ((t) BuNC)3}(+) (3). According to DFT calculations, 1 and 2 can be described as closed-shell species that are electron-deficient in terms of the Wade-Mingos rules because the apical ZnCp* units that constitute the cluster cage do not have three, but only one, frontier orbitals available for cluster bonding. Zinc behaves flexibly in building the skeletal metal-metal bonds, sometimes providing one major frontier orbital (like Group 11 metals) and sometimes providing three frontier orbitals (like Group 13 elements).

The σ-aromatic clusters [Zn3]⁺ and [Zn2Cu]: embryonic brass.

The triangular clusters [Zn3Cp*3](+) and [Zn2CuCp*3] were obtained by addition of the in situ generated, electrophilic, and isolobal species [ZnCp*](+) and [CuCp*] to Carmona's compound, [Cp*Zn-ZnCp*], without splitting the ZnZn bond. The choice of non-coordinating fluoroaromatic solvents was crucial. The bonding situations of the all-hydrocarbon-ligand-protected clusters were investigated by quantum chemical calculations revealing a high degree of σ-aromaticity similar to the triatomic hydrogen ion [H3](+). The new species serve as molecular building units of Cu(n)Zn(m) nanobrass clusters as indicated by LIFDI mass spectrometry.

A solvated zinc analogue of the calomel-dication.

The synthesis and characterisation of the solvent-stabilized salt [Zn2(THF)6](2+)[BAr4(F)]2(-) (1) is presented, which features the dizinc dication [Zn2](2+) as an analogue of the calomel dication [Hg2](2+). The labile tetrahydrofuran (THF) solvate molecules of 1 can be readily substituted by other ligands. Reaction with the strong donor ligand PMe3 (Me = CH3) leads to the Zn(ii) complex [Zn(PMe3)4](2+)[BAr4(F)]2(-) by disproportionation, while the π-acceptor-ligand phenylisocyanide (PhNC) gives the substitution product [Zn2(PhNC)6](2+)[BAr4(F)]2(-) (2) with an intact Zn-Zn bond.

Dizinc cation [Zn2](2+) trapped in a homoleptic metalloid coordination environment stabilized by dispersion forces: [Zn2(GaCp*)6][BAr4(F)]2.

The synthesis and characterization of the cationic mixed metal Ga/Zn cluster [Zn2(GaCp*)6](2+) (1) is presented. The reaction of [Zn2Cp*2] with [Ga2Cp*][BAr4(F)] leads to the formation of the novel complex being the first example of a [Zn2](2+) core exclusively ligated by metalloid group-13 organyl-ligands. Compound 1 exhibits two different coordination modes: In the solid state, two of the six GaCp* ligands occupy bridging positions, whereas VT (1)H NMR indicates the coexistence of a second isomer in solution featuring six terminal GaCp* ligands. Quantum chemical calculations have been carried out to assign the gallium and zinc positions; the bonding situation in 1 is characterized and the importance of dispersion forces is discussed.

Molecular brass: Cu4Zn4, a ligand protected superatom cluster.

The first example of ligand protected Cu-Zn clusters is described. Reaction of [CpCu(CN(t)Bu)] with [Zn2Cp*2] yields [(CuCN(t)Bu)4(ZnCp*)4] (1a) and [(CuCN(t)Bu)4(ZnCp*)3(ZnCp)] (1b). According to DFT calculations, the [Cu4Zn4] unit fulfils the unified superatom model for cluster valence shell closing.

Cp* as a removable protecting group: low valent Zn(I) compounds by reductive elimination, protolytic and oxidative cleavage of Zn-Cp*.

Zn-Cp* bond cleavage reactions leading to novel monovalent cationic zinc species are presented (Cp* = pentamethylcyclopentadienyl). The treatment of [Zn2Cp*2] with two equiv. of [H(Et2O)2][BAr4(F)] (BAr4(F) = B{C6H3(CF3)2}4) yields the triple-decker complex [Cp*3Zn4(Et2O)2][BAr4(F)] (1) via protolytic removal of a Cp* ligand as Cp*H, whereas the reaction with an equimolar amount of [FeCp2][BAr4(F)] (Cp = cyclopentadienyl) results in the formation of [Cp*Zn2(Et2O)3][BAr4(F)] (2) under oxidative cleavage of a Cp* ring giving decamethylfulvalene, (Cp*)2, and [FeCp2] as by-products. The molecular structures of compounds 1 and 2 are established by single-crystal X-ray diffraction studies. A new synthetic pathway for the formation of [Zn2Cp*2] based on the reductive elimination of Cp*H from in situ formed Cp*ZnH is presented.