Synthesis of Thiostannates, Oxo-Thiostannates and Tin-Sulfides Applying Transition Metal Complexes Containing Macrocyclic Amine Molecules : Development of new synthetic routes to synthesize Sn-S and S-Sn-O compounds and investigation of their properties

The aims of the present work were the synthesis and characterization of new thiostannates, oxo-thiostannates and tin-sulfide compounds. The salt Na4SnS414H2O was used as precursor, which was reacted with transition metal complexes containing macrocyclic amine ligands. The advantage of macrocyclic amine ligands is on the one hand they form very stable complexes and on the other hand they provide one or two free coordination sites so that a bond formation between thiostannate anion and transition metal cation is possible, if the transition metal cation prefers an octahedral environment. The formation of Na4SnS4·14H2O was investigated demonstrating that Na4SnS4·14H2O could be prepared through a new simple procedure reacting Na2S9H2O with SnCl45H2O in H2O at room temperature. For the precipitation of the product dried acetone was added to the aqueous solution. Furthermore, the stability of Na4SnS4·14H2O was investigated indicating that Na4SnS4·14H2O transforms slowly to the new compound Na4Sn2S6·5H2O in the solid state. The formation of Na4Sn2S6·5H2O probably requires a protonation of the terminal S2- anions and condensation of the protonated species under release of H2S. In addition, the stability of Na4SnS4·14H2O in H2O was investigated by 119Sn-NMR spectroscopy demonstrating that the [Sn2S6]4- anions were formed very fast in aqueous solution. Na4SnS414H2O was reacted with the complexes [Ni(cyclen)](ClO4)2 and [Ni(cyclen)(H2O)2](ClO4)2H2O under hydrothermal conditions leading to the generation of new oxo-thiostannate compounds: {[Ni(cyclen)]6[Sn6S12O2(OH)6]}2(ClO4)19H2O and [Ni(cyclen)(H2O)2]4[Sn10S20O4]~13H2O (cyclen = 1,4,7,10-tetraazacyclododecane). The crystal structure of {[Ni(cyclen)]6[Sn6S12O2(OH)6]}2(ClO4)19H2O is constructed by the rare cluster [Sn6S12O2(OH)6]10- and six Ni2+ centered complexes which are covalently bonded to the cluster via Ni–S und Ni–OH bonds. In [Ni(cyclen)(H2O)2]4[Sn10S20O4] ~13H2O only isolated cations and anions are observed. Both compounds display good photocatalytic activity for H2 generation. Investigations of the thermal properties of both compounds indicate that the water molecules of [Ni(cyclen)(H2O)2]4[Sn10S20O4]~13H2O can be reversibly removed and incorporated without structural collapse. However, the crystal water of {[Ni(cyclen)]6[Sn6S12O2(OH)6]}2(ClO4)19H2O cannot be reversibly removed and treatment with small amounts of water was required leading to the generation of the pristine material and an unidentified phase. Using the [Cu(cyclam](ClO4)2 complex (cyclam = 1,4,8,11-tetraazacyclotetradecane) the new layered compound {[Cu(cyclam)]2[Sn2S6]}n2nH2O could be obtained, which is the first thiostannate compound containing Cu(II) cations. {[Cu(cyclam)]2[Sn2S6]}n2nH2O was synthesized at room temperature using H2O as solvent. In the crystal structure distorted CuN4S2 octahedra are observed. The distortion of the octahedra was confirmed by EPR spectroscopy. The sample can be dehydrated and rehydrated without changing the crystallinity of the material. Similar to the synthesis of {[Cu(cyclam)]2[Sn2S6]}n2nH2O, syntheses were performed using the complexes [Ni(L1)](ClO4)2 and [Ni(L2)](ClO4)2 (L1 = 1,8-dimethyl- 1,3,6,8,10,13-hexaazacyclotetradecane and L2 = 1,8-diethyl-1,3,6,8,10,13- hexaazacyclotetradecane) at room temperature leading to crystallization of new compounds: [Ni(L1)][Ni(L1)Sn2S6]n∙2H2O and [Ni(L2)]2[Sn2S6]∙4H2O. Since the complexes [Ni(L1)](ClO4)2 and [Ni(L2)](ClO4)2 are poorly soluble in water but exhibit a good solubility in organic solvents like acetonitrile or dimethylsulfoxide, syntheses were carried out by overlaying an aqueous solution of Na4SnS4∙14H2O with the [Ni(L1)](ClO4)2 complex dissolved in acetonitrile or by overlaying a solution of the [Ni(L2)](ClO4)2 complex dissolved in dimethylsulfoxid with an aqueous solution of Na4SnS4∙14H2O.


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