Synthesis and Characterization of MoFe3S4 and Mo2Fe2S4 Single Cubanes

Variations in the Interplay of Intermetallic and Metal Chalcogenide Units in Organotin-Copper Selenide Clusters

We report the formation and structures of two new organotin-copper selenide clusters that were obtained in a two-step procedure. First, [(R¹Sn)₄Se₆] [R¹ = CMe₂CH₂C(O)Me] is reacted with [Cu(PPh₃)₃Cl] and (SiMe₃)₂Se to form a bright-orange powder, the nature of which could not be identified in detail, yet a suspension of it in CH₂Cl₂ reacts with N₂H₄·H₂O to afford single crystals of two cluster compounds, either [(Cu₃Sn){(R²Sn)₂Se₄}₂{(R²Sn₂)Se₃}] (1) or [(N₂H₄)(Cu₄Sn){(R²Sn)₂Se₄}₃] [2; R² = CMe₂CH₂C(NNH₂)Me]. Both are based on an intermetallic Cu_xSn cluster core (x = 3, 4), which is surrounded by organotin selenide units in different fashions. The results foster the assumption of a complex equilibrium to be present in according reaction mixtures.

Ternary Mixed-Valence Organotin Copper Selenide Clusters

Reactions of the organotin selenide chloride clusters [(R¹ Sn^IV )₃ Se₄ Cl] (A, R¹ =CMe₂ CH₂ C(O)Me) or [(R¹ Sn^IV )₄ Se₆ ] (B) with [Cu(PPh₃ )_3-x Cl_x ] yield cluster compounds with different inorganic, mixed-valence core structures: [Cu₄ Sn^II Sn^IV₆ Se₁₂ ], [Cu₂ Sn^II₂ Sn^IV₄ Se₈ Cl₂ ], [Cu₂ Sn^II Sn^IV₄ Se₈ ], [Cu₂ Sn^II₂ Sn^IV₂ Se₄ Cl₄ ], and [Cu₂ Sn^IV₂ Se₄ ]. Five of the compounds, namely [(CuPPh₃ )₂ {(R¹ Sn^IV )₂ Se₄ }] (1), [(CuPPh₃ )₂ Sn^II {(R² Sn^IV )₂ Se₄ }₂ ] (2), [(CuPPh₃ )₂ (Sn^II Cl)₂ {(RSn^IV )₂ Se₄ }₂ ] (3) [(CuPPh₃ )₂ (Sn^II Cu₂ ){(R¹ Sn^IV )₂ Se₄ }₃ ] (4), and [Cu(CuPPh₃ )(Sn^II Cu₂ ){(R¹ Sn^IV )₂ Se₄ }₃ ] (5) are structurally closely related. They are based on [(CuPPh₃ )₂ {(RSn^IV )₂ Se₄ }_n ] aggregates comprising [(RSn^IV )₂ Se₄ ] and [CuPPh₃ ] building units, which are linked by further metal atoms. A sixth compound, [(CuPPh₃ )₂ (Sn^II Cl)₂ {(R¹ Sn^IV Cl)Se₂ }₂ ] (6), differs from the others by containing [(RSn^IV Cl)Se₂ ] units instead, which affects the absorption properties. The compounds were analyzed by single-crystal X-ray diffraction, NMR and ¹¹⁹ Sn Mössbauer spectroscopy, DFT calculations as well as optical absorption experiments.

The [MoFe3S4]2+ oxidation state: synthesis, substitution reactions, and structures of phosphine-ligated cubane-type clusters with the S=2 ground state

The cluster [(Tp)MoFe(3)S(4)(PEt(3))(3)](1+) containing the cubane-type [MoFe(3)(μ(3)-S)(4)](2+) reduced core undergoes facile ligand substitution reactions at the iron sites leading to an extensive set of mono- and disubstituted species [(Tp)MoFe(3)S(4)(PEt(3))(3-n)L(n)](1-n) with L = halide, N(3)(-), PhS(-), PhSe(-), R(3)SiO(-), and R(3)SiS(-) and n = 1 and 2. Structures of 10 members of the set are reported. For two representative clusters, Curie behavior at 2-20 K indicates a spin-quintet ground state. Zero-field Mössbauer spectra consist of two doublets in a 2:1 intensity ratio. (57)Fe isomer shifts are consistent with the mean oxidation state Fe(3)(2.33+) arising from electron delocalization of the mixed-valence oxidation state description [Mo(3+)Fe(3+)Fe(2+)(2)]. Reaction of [(Tp)MoFe(3)S(4)(PEt(3))(2)Cl] with (Me(3)Si)(2)S affords [(Tp)MoFe(3)S(4)(PEt(3))(2)(SSiMe(3))], a likely first intermediate in the formation of the tricluster compound {[(Tp)MoFe(3)S(4)(PEt)(2)](3)S}(BPh(4)) from the reaction of [(Tp)MoFe(3)S(4)(PEt(3))(3)](BPh(4)) and NaSSiMe(3) in tetrahydrofuran (THF). The tricluster consists of three cluster units bound to a central μ(3)-S atom in a species of overall C(3) symmetry. Relatively few clusters in the [MoFe(3)S(4)](2+) oxidation state have been prepared compared to the abundance of clusters in the oxidized [MoFe(3)S(4)](3+) state. This work is the first comprehensive study of the [MoFe(3)S(4)](2+) state, one conspicuous feature of which is its ability to bind hard and soft σ-donors and strong to weak π-acid ligands. (Tp = tris(pyrazolyl)hydroborate(1-)).

Dimerization of pentanuclear clusters [Fe3Q(AsMe)(CO)9] (Q = Se, Te) as a conversion pathway to novel cubane-like aggregates

The first examples of carbonyl heterocubane-type clusters, [Fe(4)(μ(3)-Q)(2)(μ(3)-AsMe)(2)(CO)(12)] (2, Q = Se (a), Te (b)), which simultaneously contain elements of group 15 and 16, were obtained by thermolysis of [Fe(3)(μ(3)-Q)(μ(3)-AsMe)(CO)(9)] (1) in acetonitrile. The clusters 2 possess a cubic Fe(4)Q(2)As(2) core with alternating Fe and Q/As atoms. The coordination environment of the Fe atoms is close to octahedral, and those of Q or As atoms are tetrahedral, which determines the distorted cubic cluster core geometry. The second main products of thermolysis are the clusters [Fe(6)(μ(3)-Q)(μ(4)-Q)(μ(4)-AsMe)(2)(CO)(12)] (3a,b), whose core contains double the elemental composition of the initial cluster 1. In the case of the Se-containing cluster two other minor products [Fe(4)(μ(4)-Se)(μ(4)-SeAsMe)(CO)(12)] (4) and [Fe(3)(μ(3)-AsMe)(2)(CO)(9)] (5) are formed. Based on the structures and properties of the products, a reaction route for the conversion of 1 into 2 is proposed, which includes the associative formation of the clusters 3 as intermediates, unlike the dissociative pathways previously known for the transformations of similar clusters of the type [Fe(3)Q(2)(CO)(9)].