Quantenchemische Untersuchungen zu Stabilitäten und Reaktivitäten binärer Zintl-Anionen und intermetalloider Cluster und zu organisch funktionalisierten Münzmetall-Chalkogenid-Clustern

In the course of this PhD thesis, systematic quantumchemical investigations were performed reagarding reactivities and stabilities of binary Zintl anions and intermetalloid clusters, as well as of binary and ternary coinage metal chalcogenide clusters. The studies of binary, pseudotetrahedral Zintl anions consisting of atoms of groups 13 to 15 were discussed first. By applying DFT methods, stable minimum structures on the potential energy surface could be found for all 48 possible element combinations. Those anions that should be synthesizable were identified based on the inspection of the covalent radii. The anions of type (TrTt3)5− or (TrPn3)2− with a ratio of the covalent radii of 1 or slightly less are favored. This is due to the effect that longer Tt–Tt or Pn–Pn bonds make a closer approach of the Tr atoms towards the center of the trigonal bases possible, similar to a close-packed lattice, which leads to the formation of stronger bonds. This does not apply to the anions of the type (Tt2Pn2)2− because of their element element ratio of 1:1. In this case, those anions with only small differences of the radii are favored. Examining the electronic properties of said anions showed possible derivatization patterns. Doubly protonating the anions yielded bridged bonds of the respective anions and the formation of 3c2e interactions. These clusters were highly favored in comparison to the face-centered isomers. Because of the higher steric demand of trimethylsilyl groups the structural motives obtained upon doubly silylating the anions became much more versatile compared to the protonated species. It could be furthermore shown that the applicability of the anions [{CpFe(CO)2}2(Tt2P2)]2− and [{CpFe(CO)2}2(Tt2As2)]2− strongly depends on the element combination within the central butterfly-like moiety. According to the pseudo-element concept the three anoins (SiP6)q−, (GeP6)q− und (SiAs6)q− should have a charge of 4−. However, only two counterions were found. This led to the assumption that these anions are doubly protonated. Further studies showed that the group 14 atom is most likely situated either in the trigonal cluster base or in the apical position. Two of the three two-bonded sites are protonated, since the atoms here have the highest negative partial charge, according to population analyses. Similar studies were undertaken for the intermetalloid clusters [Nb@As8Hm]n− and [Nb@As11Hp]q−. According to the pseudo-element concept the first cluster should have a structure analogous to the S8 ring in monoclinic sulphur with an overall charge of 3−. The second cluster should have a charge of 4−. Yet again, only two counterions were detected. Calculated structural data and the simulation of IR spectra showed, that [Nb@As8H]2− with the proton bridging an As•••Nb contact seemed to be most plausible. For the second cluster the calculations yielded two different isomers of the oubly protonated anion [Nb@As11H2]2−. The investigations shown in this chapter are still ongoing since the calculated and the experimental data match poorly. In part two of this PhD thesis, binary and ternary coinage metal chalcogenide clusters were investigated. In a first study palladophilic interactions and multicenter interactions were proven to stabilize the trigonal bipyramidal cluster core within the two cations [Pd3(PPh3)5(SeH)(μ3-Se)2]+ and [Pd3(PPh3)5(SnCl3)(μ3-Se)2]+. Significant multicenter interactions were also shown to exist in the [(SnR)2Se4] moieties in a series of copper containing ternary clusters. They are also responsible for the color of the respective clusters since the LUMO is located at these moieties. The calculated HOMO LUMO gaps correspond well with the observed colors. Clusters without [(SnR)2Se4] moieties are colorless. No cuprophilic interactions could be detected in this cluster series. The two ternary tin-silver selenide clusters [Ag6(μ6-Se)(Ag8Se12){(R1Sn2)Se2}6] (R1: CMe2CH2C(O)Me) and [Ag7(μ7-Se)(Ag7Se12){(R2Sn2)Se2}6] (R2: CMe2CH2C(NNH2)Me) contain isomeric cluster cores. The first cluster is more symmetric than the second one and, according to the comparison of total energies, favored for both organic functional groups. This implies that the second cluster might be a kinetic product. The last study focused on the investigation of the high-nuclearity gold(I) sulfido complex [Au10S2(PPh2)2(dppma2)4(dppma3)]∙[Au6S2(dppma2)2(dppma3)], which is composed of two neutral subunits. Quantumchemical calculations showed that these subunits are solely held together by S•••H and O•••H bridges, each of which contributes −54 kJ•mol−1. Aurophilic or Au•••S dipole interactions do not play a significant role in stabilizing the molecular structure.