Atom Exchange Versus Reconstruction: (Gex As4-x )x- (x=2, 3) as Building Blocks for the Supertetrahedral Zintl Cluster [Au6 (Ge3 As)(Ge2 As2 )3 ]3

The Zintl anion (Ge2 As2 )2- represents an isostructural and isoelectronic binary counterpart of yellow arsenic, yet without being studied with the same intensity so far. Upon introducing [(PPh3 )AuMe] into the 1,2-diaminoethane (en) solution of (Ge2 As2 )2- , the heterometallic cluster anion [Au6 (Ge3 As)(Ge2 As2 )3 ]3- is obtained as its salt [K(crypt-222)]3 [Au6 (Ge3 As)(Ge2 As2 )3 ]⋅en⋅2 tol (1). The anion represents a rare example of a superpolyhedral Zintl cluster, and it comprises the largest number of Au atoms relative to main group (semi)metal atoms in such clusters. The overall supertetrahedral structure is based on a (non-bonding) octahedron of six Au atoms that is face-capped by four (Gex As4-x )x- (x=2, 3) units. The Au atoms bind to four main group atoms in a rectangular manner, and this way hold the four units together to form this unprecedented architecture. The presence of one (Ge3 As)3- unit besides three (Ge2 As2 )2- units as a consequence of an exchange reaction in solution was verified by detailed quantum chemical (DFT) calculations, which ruled out all other compositions besides [Au6 (Ge3 As)(Ge2 As2 )3 ]3- . Reactions of the heavier homologues (Tt2 Pn2 )2- (Tt=Sn, Pb; Pn=Sb, Bi) did not yield clusters corresponding to that in 1, but dimers of ternary nine-vertex clusters, {[AuTt5 Pn3 ]2 }4- (in 2-4; Tt/Pn=Sn/Sb, Sn/Bi, Pb/Sb), since the underlying pseudo-tetrahedral units comprising heavier atoms do not tend to undergo the said exchange reactions as readily as (Ge2 As2 )2- , according to the DFT calculations.

Systematic DFT Studies on Binary Pseudo-tetrahedral Zintl Anions: Relative Stabilities and Reactivities towards Protons, Trimethylsilyl Groups, and Iron Complex Fragments

Binary pseudo-tetrahedral Zintl anions composed of (semi)metal atoms of the p-block elements have proven to be excellent starting materials for the synthesis of a variety of heterometallic and intermetalloid transition metal-main group metal cluster anions. However, only ten of the theoretically possible 48 anions have been experimentally accessed to date as isolable salts. This brings up the question whether the other species are generally not achievable, or whether synthetic chemists just have not succeeded in their preparation so far. To contribute to a possible answer to this question, global minimum structures were calculated for all anions of the type (TrTt3 )5- , (TrPn3 )2- , and (Tt2 Pn2 )2- , comprising elements of periods 3 to 6 (Tr: triel, Al⋅⋅⋅Tl; Tt: tetrel, Si⋅⋅⋅Pb; Pn: pnictogen, P⋅⋅⋅Bi). By analyzing the computational results, a concept was developed to predict which of the yet missing anions should be synthesizable and why. Additionally, the results of an electrophilic attack by protons or trimethylsilyl groups or a nucleophilic attack by transition metal complex fragments are described. The latter yields butterfly-like structures that can be viewed as a new form of adaptable tridentate chelating ligands.

[Co@Sn6 Sb6 ]3- : An Off-Center Endohedral 12-Vertex Cluster

We report on the asymmetric occupation of a 12-vertex cluster centered by a single metal atom. Three salts of related intermetalloid cluster anions, [Co@Sn₆ Sb₆ ]^3- (1), [Co₂ @Sn₅ Sb₇ ]^3- (2), and [Ni₂ @Sn₇ Sb₅ ]^3- (3) were synthesized, which have pseudo-C_4v -symmetric or pseudo-D_4h -symmetric 12-vertex Sn/Sb shells and interstitial Co^- ions or Ni atoms. Anion 1 is a very unusual single-metal-"centered" 12-atom cluster, with the inner atom being clearly offset from the cluster center for energetic reasons. Quantum chemistry served to assign atom types to the atomic positions and relative stabilities of this cluster type. The studies indicate that the structures are strictly controlled by the total valence electron count-which is particularly variable in ternary intermetalloid cluster anions. Preliminary ¹¹⁹ Sn NMR studies in solution, supported by quantum-chemical calculations of the shifts, illustrate the complexity regarding Sn:Sb distributions of such ternary systems.

Between Localization and Delocalization: Ru(cod)2+ Units in the Zintl Clusters [Bi9 {Ru(cod)}2 ]3- and [Tl2 Bi6 {Ru(cod)}]2

Reactions of [K(crypt-222)]₂ (TlBi₃ )⋅0.5 en (1 b) with [Ru(cod)(H₂ CC(Me)CH₂ )₂ ] (A) in 1,2-diaminoethane (en) led to the formation of two compounds with new bismuth-rich cluster anions, [K(crypt-222)]₃ [Bi₉ {Ru(cod)}₂ ]⋅1.5 en (2) and [K(crypt-222)]₂ [Tl₂ Bi₆ {Ru(cod)}]⋅2 tol (3), alongside the salt of a binary nido cluster, [K(crypt-222)]₃ (Tl₄ Bi₅ )⋅2 en (4). The anions in 2 and 3 are two further examples of rare heterometallic clusters containing Ru atoms. As one cod ligand is retained on each Ru atom in both clusters, the anions may be viewed as intermediates on the way towards larger, ligand-free intermetalloid clusters. Quantum-chemical studies provided insight into the bonding situation in these clusters. According to these studies, the anion of 2 features both electron-precise and electron-deficient parts. Electrospray ionization mass spectrometry analysis indicated that the clusters undergo stepwise fragmentation.

Bismuthanes as Hemilabile Donors in an O2 -Activating Palladium(0) Complex

A xanthene-based bismuthane/phosphane chelating ligand has been accessed that has enabled the synthesis of a palladium(0) bismuthane complex. The bismuthane donor proved to be hemilabile as it switched to a dangling position upon addition of O₂ that gave a palladium(II) peroxide complex. Unlike the corresponding 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) palladium peroxide, the bismuth analogue could be employed for catalytic phosphane oxidation and oxidative phenol coupling.

{[CuSn5 Sb3 ](2-) }2 : A Dimer of Inhomogeneous Superatoms

Reaction of the binary Zintl anion (Sn2 Sb2 )(2-) with the β-diketiminato complex [LCu(NCMe)] (L=nacnac=[(N(C6 H3 (i) Pr2 -2,6)C(Me))2 CH](-) ) in ethylenediamine or DMF affords the ternary cluster dimer {[CuSn5 Sb3 ](2-) }2 (1) as its [K(crypt-222)](+) salt. The chemical formulation of 1 is supported by energy-dispersive X-ray spectroscopy (EDX) and quantum chemical calculations. Each monomeric part of the dimer represents a trimetallic "[CuSn5 Sb3 ](2-) " cluster, with an architecture in between a tricapped trigonal prism and a capped square antiprism. As shown by quantum chemical investigations, the presence of Sb atoms and, in particular, of Cu atoms in the cluster skeleton makes the monomeric unit behave like an inhomogeneous superatom, which clearly prefers to dimerize, thereby producing a relatively short, yet virtually non-bonding Cu⋅⋅⋅Cu distance.

Origin and location of electrons and protons during the formation of intermetalloid clusters [Sm@Ga(3-x)H(3-2x)Bi(10+x)](3-) (x = 0, 1)

Reaction of [GaBi3](2-) with [Sm(C5Me4H)3] yielded the first protonated ternary intermetalloid clusters [Sm@Ga(3-x)H(3-2x)Bi(10+x)](3-) (1; x = 0,1). The presence of the Ga-H bonds and the transfer of electrons and protons during the formation of 1 were elucidated by a combination of experimental and quantum chemical methods, thereby rationalizing the role of the solvent ethane-1,2-diamine as a Brønsted acid. As an organic by-product, we observed the previously unknown octamethylfulvene (2) upon C-C coupling of (C5Me4H)(-).