Table of Contents:
Within the scope of this thesis, d10 metals of groups 12 and 14 were reacted with group 16 elements under solvo- and ionothermal conditions. The topic was dealt with in three parts, the results of which are summarized in the following. In part A, the focus was on the purification and increase in yield of the selenidocadmate compounds K6[CdSe4] (A) and K2[Cd3Se4] (B) synthesized in my master thesis. Therefor wet chemical methods as well as solvothermal methods were to be used. A purification of A and B was not successful but from the reaction of A with 18-crown-6 in en the compound K2[CdSe2] (1) was obtained. The anion in 1 consists of one-dimensional strands that are built of edge-sharing [CdSe]-tetrahedra. Thus, a missing link, regarding the dimensionality, between A (0D) and B (2D) was found. Still outstanding would be the synthesis of a three-dimensional [CdSe]-network, for example K2[Cd6Se7] analogous to K2[Hg6Se7].
In part B the compounds A and B that were synthesized in part A were reacted with the selenidostannate compounds [K(H2O)]4[SnSe4] (C) and K2[Sn2Se5] (D) under ionothermal conditions to prepare novel compounds that combine structural features of zeolites and electronical properties of II/VI or IV/VI semi-conductors. From the reaction of A and D in (C4C1C1Im)[BF4] with en as auxiliary, the compound (C4C1C1Im)4[Cd2Sn2Se4] (i) was obtained. By single crystal xray diffraction it was only possibe to determine a unit cell, which showed the same cell parameters as the compound (C4C1C1Im)4[Hg2Sn2Se4], that was synthesized earlier by C. DONSBACH. Therefore it was assumed that that the anion in i was isostructral to the anion [Hg2Sn2Se4]4− and a corresponding structure was suggested. By using methanol as auxiliary with the same mixture of educts the compound (C4C1C1Im)4[CdxSn20-xSe35] (2) was built. The anoin in 2 is a T4-supertetrahedron made from corner-sharing [MSe4]-tetrahedra in which both Sn and Cd atoms are incorporated into the anion, as in i. Neither in i nor in 2 a clear assignment of Sn or Cd atoms to the metal positions in the anionic structures could be carried out. Measurements still have to be made to confirm the suggested structure of i. In i as well as in 2 the assignments of Sn and Cd atoms in the anionic structure must be determined and the investigation of physical properties of i and 2 is still lacking.
In a next step, the chemistry of selendiometalate compounds was transferred to corresponding complexes of the transition metal tungsten and the compound K4[WO2Se2][WOSe3] (3) was synthesized in a high temperature solid state reaction of K2Se with W and Se with following solvothermal extraction in methanol. The anion in 3 consists of two W atoms of which one is surrounded by two Se and two O ligands whereas the other one is surrounded by three Se ligands and one O ligands. By reacting the solid mixture K2[WSe4]/WSe2 obtained by the high temperature reaction with D in (C4C1C1Im)[BF4] the known compound (C4C1C1Im)4[Sn6Se14] as well as the new compound (C4C1C1Im)2[WSe4] (4) were isolated. Compound 4 is a salt of the [WSe4]2− anion whose charge is balanced by two IL cations. After investigating wether 4 is a IL per definition, reactions can be carried out in which 4 can be a source for both W and Se atoms.
In part C the synthesis of a „zeoball“ salt was used as starting point and then varied and extended. At first, the effect of the addition of the metallocenium salts [Cp2Fe][BF4] and [Cp2Co][PF6] on the building of products was investigated. Here, three unit cells were determined whose dimensions suggest „zeoball“ salts ii – iv As far as analyses were possible, in none oft he compounds IL cations were replaced by metallocenium cations. To enforce this the IL (Cp2FeC1C1Im)I (5) was synthesized, which carries a ferrocenyl substituent at the imidazolium ring. Reactions in it did not lead to any crystalline products yet. Further investigations in incorporating small molecules into the „zeoball“ anion are to be made by using less redoxactive substances. Also, suitable reaction conditions for the use of 5 as IL have tob e found.
In further investigations the focus was on the replacement of Sn or Ge atoms in the „zeoball“ anion by transition metal atoms like Ti or Zr. Therefore [K4(H2O)3][Ge4Se10] (E) was not reacted with SnCl4∙5H2O but with TiCl4 or ZrCl4 in ILs. A reaction with TiCl4 in (C2C1Im)[B(CN)4] lead tot he formation of (C2C1Im)6[Ge8Se19] (6). During the investigation of 6 it was shown that the use of TiCl4 is not necessary but the nature of the IL was crucial. So the formation of 6 could not be observed by when ILs containing F− ions were used. Still the physical properties of 6 have to be determined.
In order to lower the reactivity of TiCl4 and to achieve a better control of the reaction process, TiCl4 was reacted with (C4C1C1Im)Cl in advance and (C4C1C1Im)2[TiCl6] (7) was obtained. However, ionothermal reactions of E with 7 did not result in the formation of crystalline products. In the future, the right reaction conditions to get crystalline products from reactions with 7, different ILs as reaction media and different reaction temperatures should be used.
In analogy to the inclusion of I2 into the anion of the „zeoball“ salt F, as described in the introduction, a corresponding study was carried out with a solution of Br2 in cyclohexane. In this, a change of colour of the solution and of the „zeoball“ salt crystals was observed as well. UV/Vis spectroscopy of the supernatant enabled monitoring of the process. Weighing the crystals after the experiment showed an increase in mass, that was confirmed by TGA measuremnts. In the following treatment of the crystals in ethanol again a change of colour was observed and monitored by UV/Vis spectroscopy. The reaction allowed inference on the release of Br− and the formation of Br3−.
In part C, syntheses were also performed in different ILs. First the highly reactive IL (C6C1Im)Br9 was used as reaction medium but seemed to decay the educs very quickly so it was used only as additive and (C4C1C1Im)2[SnBr6] (8) was obtained. After investigating if 8 is a IL per definition, reactions could be performed in which 8 might act as both reaction media and source for Sn atoms.
Reactions in the ILs (C4ImC8ImC4)Br2 and (C4ImC8ImC4)[BF4]2, that contain bications lead to the formation of (Cat)4[Sn7Se16] (9), the anion of which consists of a new selenidostannate network structure. Furthermore a new „zeoball“ salt (C4ImC8ImC4)14[Ge18Sn42Se134] (10) was synthesized in bi-cat ILs. Compared to the anion in F, the anion in 10 comprises a slightly different composition and a different structure. The anionic substructure in 10 is formed by 14 [Sn3Se7] defect heterocubane units, 12 of which are linked in a zig-zag fashion by µ-Se bridges to form a ring. The two remaining defect heterocubane units as well as 6 [Ge3Se9] building units are located above and below the ring. Thus, the anion in 10 shows pseudo-D3d-symmetry and is a bit smaller than the anion in F with an outer diameter of 24,3 Å (23,9 Å in F).
Finally, syntheses for the formation of „zeoball“ salts were performed in Tunable Aryl Alkyl Ionic Liquids (TAAILs). From syntheses in these sterically demanding ILs with the general formula [PhRCnIm][NTf2], in the case of n = 4 a new „zeoball“ salt [Ph4-BrC4Im]24[Ge24Sn36Se132] (11) was formed, as well as the two compounds [Ph4-MeC4Im][DMMPH][Ge0,9Sn2,1Se7] (12) and
[Ph4-BrC4Im][DMMPH][GeSn2Se7] (13), that have one-dimensional strands as anions. In the TAAIL with n = 12 the compound K2[Sn3Se7] (14) was synthesized, in which the anionic substructure is a two-dimensional layer and not the cations of the IL balance the charge, but K+ cations.
In the framework of this thesis a total of 18 new compounds were synthesized. For four of these compounds (i – iv) it was only possible to determine unit cells due to lo single crystal diffraction data quality. Based on the dimensions of the unit cells and due to previous knowledge, strucutre suggestions were made. By single crystal xray diffraction it was possible to determine the structures oft he other compounds 1 – 14. Not in all compounds the cations could be located in single crystal structure determination. Still a broad spectrum of anionic substructures was determined, ranging from IL salts with molecular anions (4 – 8) to anionic strands (12, 13) to a new three-dimensional network (9). In addition, a new „zeoball“ salt (10) was prepared.