Coordinatively Unsaturated Polynuclear Mixed-Valent SnII–SnIV and CuII–SnIV Oxo-Centered Carboxylates

Hydrated and Solvated Tin(II) Ions in Solution and the Solid State, and a Coordination Chemistry Overview of the d10 s2 Metal Ions

The coordination chemistry of d¹⁰ s² metal ions is strongly affected by an (at least partially) occupied d¹⁰ s² metal ion-ligand atom antibonding orbital, which may cause a void in the coordination sphere due to repulsion between the electrons in the antibonding orbital on the metal ion and those on the ligands. The character of the formed d¹⁰ s² metal ion-ligand atom bond plays an important role in the electron density in the antibonding orbital and thereby also in the coordination chemistry. The hydrated tin(II) ion, [Sn(H₂ O)₃ ]²⁺ , and the trihydroxidostannate ion, [Sn(OH)₃ ]^- , have very different mean Sn-O bond lengths (2.21 and 2.08 Å, respectively) and O-Sn-O angles (ca. 78 and 90°, respectively) both in the solid state and in solution. On increasing the covalency of the tin(II)-ligand bonds, the repulsion decreases and higher coordination numbers are obtained, as seen in the dimethylsulfoxide- and N,N-dimethylthioformamide-solvated tin(II) ions, both of which are five-coordinate with square-pyramidal structures.

Building a two-dimensional network from mixed-valence copper units held together by acetone bridges

The mixed-valence supramolecular product di-μ2-acetone-di-μ3-trifluoroacetato-deca-μ2-trifluoroacetato-octacopper(I)dicopper(II), [Cu10(C2F3O2)12(C3H6O)2] or {[Cu(I)4(O2CCF3)4]2-{μ2-OC(CH3)2}2-[Cu(II)2(O2CCF3)4]}, was prepared by co-deposition of two building units, namely a bis-acetone adduct of [Cu(II)2(O2CCF3)4] and a very electrophilic tetranuclear [Cu(I)4(O2CCF3)4] complex. The asymmetric unit contains one molecule of the compound with a total of ten independent Cu atoms. Acetone molecules serve as bridges between the [Cu(II)2(O2CCF3)4] and [Cu(I)4(O2CCF3)4] units. Additionally, the tetracopper(I) trifluoroacetate units are involved in intermolecular Cu···O interactions, forming a layered two-dimensional network in the extended structure.