Untersuchungen zur Anbindung von organischen Liganden an Sn/S-Cluster zum potenziellen Einfang von Übergangsmetallionen

Three methods were developed to either functionalize the Sn/S cluster A, [(RSn)4S6] A with R: (Me)OCCH2CMe2, with organic substituents which can serve as complexating agents for transition metals or to functionalize A with precoordinated complexes. The first method consists of reacting a precoordinated transition metal complex possessing a hydrazone or hydrazine functionality with the keto groups of A. This approach was successfully demonstrated for ruthenocene, which was first activated as acetylruthenocene RcAcNNH2. The hydrazone compound readily reacted with A. Single crystal X-ray diffraction showed a reorganization of the inorganic cluster core from the Sn4S6 topology to Sn6S10, the topology, with preservation of four organic substituents in compound [(RRcSn)4Sn2S10] (RRc: CMe2CH2C(Me)=N–N=C(Me)Rc, Rc: (C5H5)2Ru) (2). This phenomenon was observed for all subsequently performed functionalizations of A as well. The electrochemical and optical properties of 2 were examined in detail. 2 shows broad luminescence band at 500 nm could be observed and attributed to both the inorganic cluster core and the metal organic ligand. Attempts to tether other, more reactive precoordinated transition metal complexes to A in the same fashion were unsuccessful. It appears that only stable, 18 valence electron complexes can be used to perform this functionalization without decomposition. The second method is to functionalize A with hydrazine first and subsequently react the hydrazone derivative A’ with aldehydes, ketones or acetales. During the course of the investigations, it became apparent that ketones show insufficient reactivity and that the more reactive aldehydes can be used for functionalization. Reaction of A with 3-Methyl-2-butenale led to the butene functionalized cluster [(RBuSn)4Sn2S10] with RBu: CMe2CH2C(Me)=N-N=C(H)C=CMe2. Tethering an acetale to the cluster was only successful in one case, using 2-Furaldehyde-diethyl acetale to produce the cluster [(RFuSn)4Sn2S10] with RFu: CMe2CH2C(Me)=N-N=C(H)C4H3O. This underlines the great influence of the acetale substituent on the reactivity of the whole molecule. Altogether, the hydrazone-functionalized cluster A’ is considerably less reactive than its ketone precursor A, so this method is generally the least promising route for functionalization. The third method combines A and hydrazone functionalized ligands possessing donor atoms to give products that can then react with transition metals. During the course of the investigations, it became evident that the reactivity of the hydrazines H2N-NHR towards A varies greatly depending on the organic substituents R. While 2-Hydrazinobenzothiazole reacts with A to form the functionalized cluster [(RBT Sn)4Sn2S10] with RBT : CMe2CH2C(Me)=N-N-[C(S,N)C2]C4H4, 2,2’:6’2”-4’-Hydrazino-Terpyridine doesn’t show any reaction, possibly due to its outstanding complexation properties which may come along with chelated tin atoms. Photoluminescene measurements on the furan and benzothiazole decorated clusters 5 and 6 in comparison with the ruthenocene decorated cluster in 2 show that the (metal)organic substituents influence the luminescence properties of the compounds as they show broader signals which in case of 5 are slided to smaller wavelengths. A series of aromatic substituents with ascending size from benzaldehyde to anthracene and hetero aromatic substituents with hetero atoms in different positions, e.g. (iso-)quinoline were tethered to A. The most promising compound for capturing transition metals in this series is the 2,2’-bipyridine decorated cluster [(R6−BipySn)4Sn2S10] with R6−Bipy: CMe2CH2C(Me)=N-N=C(Me)(C5H4N−C5H3N)) (23). Unfortunately, its reaction with transition metals has so far only produced metal complexes without a cluster core attached. It is not yet clear whether these complexes result from an excess of ligand during the reaction or whether the Lewis acidic transition metal salts in combination with water molecules formed from the condensation reaction lead to a break of the ketazine bond. The reaction of 23 with Bis(1,5-cyclooctadiene)diiridium(I)dichloride led to the completely unexpected complex {[(COD)3Ir3S2]SSnCl}2 (26·2 CH2Cl2. Quantum chemical investigations of the complex show a great amount of delocalization of the Ir3S2 fragments to the point of cluster orbitals, while the central Sn2S2 ring and its bonds to the Ir3S2 fragments are built through localized 2e2c-bonds. The last method appeared the most promising route of all three, although reactions with transition metal complexes didn’t lead to the desired product.