Darstellung von Metall-Schwefel-Clustern durch einfache Reaktion von Metallsalzen mit H2S: R2(NH4)[Cu3S12], R2[Cu4S12] � CH3CN, R2[Cu4S12,8], R2[Fe2S2(S5)2], R2[Fe4S4Br4], R2[Fe4S4Br2Cl2], R2[Fe4S4Cl4], R2[Fe2S2Cl4] (R = PPh4) und [Fe(DMF)6][Fe2S2Cl4]

Adamantane-type clusters: compounds with a ubiquitous architecture but a wide variety of compositions and unexpected materials properties

The research into adamantane-type compounds has gained momentum in recent years, yielding remarkable new applications for this class of materials. In particular, organic adamantane derivatives (AdR4) or inorganic adamantane-type compounds of the general formula [(RT)4E6] (R: organic substituent; T: group 14 atom C, Si, Ge, Sn; E: chalcogenide atom S, Se, Te, or CH2) were shown to exhibit strong nonlinear optical (NLO) properties, either second-harmonic generation (SHG) or an unprecedented type of highly-directed white-light generation (WLG) - depending on their respective crystalline or amorphous nature. The (missing) crystallinity, as well as the maximum wavelengths of the optical transitions, are controlled by the clusters' elemental composition and by the nature of the organic groups R. Very recently, it has been additionally shown that cluster cores with increased inhomogeneity, like the one in compounds [RSi{CH2Sn(E)R'}3], not only affect the chemical properties, such as increased robustness and reversible melting behaviour, but that such 'cluster glasses' form a conceptually new basis for their use in light conversion devices. These findings are likely only the tip of the iceberg, as beside elemental combinations including group 14 and group 16 elements, many more adamantane-type clusters (on the one hand) and related architectures representing extensions of adamantane-type clusters (on the other hand) are known, but have not yet been addressed in terms of their opto-electronic properties. In this review, we therefore present a survey of all known classes of adanmantane-type compounds and their respective synthetic access as well as their optical properties, if reported.

Structural insight into halide-coordinated [Fe4S4XnY4-n]2- clusters (X, Y = Cl, Br, I) by XRD and Mössbauer spectroscopy

Iron sulphur halide clusters [Fe₄S₄Br₄]^2- and [Fe₄S₄X₂Y₂]^2- (X, Y = Cl, Br, I) were obtained in excellent yields (77 to 78%) and purity from [Fe(CO)₅], elemental sulphur, I₂ and benzyltrimethylammonium (BTMA⁺) iodide, bromide and chloride. Single crystals of (BTMA)₂[Fe₄S₄Br₄] (1), (BTMA)₂[Fe₄S₄Br₂Cl₂] (2), (BTMA)₂[Fe₄S₄Cl₂I₂] (3), and (BTMA)₂[Fe₄S₄Br₂I₂] (4) were isostructural to the previously reported (BTMA)₂[Fe₄S₄I₄] (5) (monoclinic, Cc). Instead of the chloride cubane cluster [Fe₄S₄Cl₄]^2-, we found the prismane-shaped cluster (BTMA)₃[Fe₆S₆Cl₆] (6) (P1̄). ⁵⁷Fe Mössbauer spectroscopy indicates complete delocalisation with Fe^2.5+ oxidation states for all iron atoms. Magnetic measurements showed small χ_MT values at 298 K ranging from 1.12 to 1.54 cm³ K mol^-1, indicating the dominant antiferromagnetic exchange interactions. With decreasing temperature, the χ_MT values decreased to reach a plateau at around 100 K. From about 20 K, the values drop significantly. Fitting the data in the Heisenberg-Dirac-van Vleck (HDvV) as well as the Heisenberg Double Exchange (HDE) formalism confirmed the delocalisation and antiferromagnetic coupling assumed from Mössbauer spectroscopy.

Halide coordinated homoleptic [Fe4S4X4](2-) and heteroleptic [Fe4S4X2Y2](2-) clusters (X, Y = Cl, Br, I)--alternative preparations, structural analogies and spectroscopic properties in solution and solid state

New facile methods to prepare iron sulphur halide clusters [Fe4S4X4](2-) from [Fe(CO)5] and elemental sulphur were elaborated. Reactions of ferrous precursors like tetrahalidoferrates(ii) or simple ferrous halides with [Fe(CO)5] and sulphur turned out to be efficient methods to prepare homoleptic [Fe4S4X4](2-) (X = Cl, Br) and heteroleptic clusters [Fe4S4X4-nYn](2-) (X = Cl, Br; Y = Br, I). Solid materials were obtained as salts of BTMA(+) (= benzyltrimethylammonium); the new compounds containing [Fe4S4Br4](2-) and [Fe4S4X2Y2](2-) (X, Y = Cl, Br, I) were all isostructural to (BTMA)2[Fe4S4I4] (monoclinic, Cc) as inferred from synchrotron X-ray powder diffraction. While the solid materials contain defined heteroleptic clusters with a halide X : Y ratio of 2 : 2, dissolving these compounds leads to rapid scrambling of the halide ligands forming mixtures of all five possible [Fe4S4X4-nYn](2-) clusters as could be shown by UHR-ESI MS. The variation of X and Y allowed assignment of the absorption bands in the visible and NIR; the long-wavelength bands around 1100 nm were tentatively assigned to intervalence charge transfer (IVCT) transitions.

Hexa-kis-(dimethyl-formamide-κO)manganese(II) μ-oxido-bis-[trichlorido-ferrate(III)]

The title compound, [Mn(C₃H₇NO)₆][Fe₂Cl₆O], was obtained unintentionally as a product of an attempted synthesis of heterometallic complexes with Schiff base ligands using manganese powder and FeCl₃·6H₂O as starting materials. In the [Fe₂OCl₆]²⁻ anion, the O atom and the Fe atom occupy positions with site symmetry and 3, respectively, resulting in a linear Fe—O—Fe angle and a staggered conformation. The octa­hedrally surrounded cation (site symmetry ) and the [Fe₂Cl₆O]²⁻ anion are alternately stacked along [001].

Synthesis and Reactivity of Haloacetato Derivatives of Iron(II) Including the Crystal and the Molecular Structure of [Fe(CF3COOH)2(μ-CF3COO)2]n

The syntheses of haloacetates of iron(II) and their reactivity are described. The compound Fe(CF3COO)2, 1, crystallizes from CF3COOH/(CF3CO)2O solution as the polynuclear [Fe(CF3COO)2(CF3COOH)2]n, 2, which contains bridging trifluoroacetates and monodentate trifluoroacetic acid groups. Fe(CF3COO)2(DMF)x, as obtained from Fe(CO)5 and CF3COOH/(CF3CO)2O in DMF, reacts with dioxygen at room temperature to give two micro3-oxo compounds, namely, [Fe3(micro3-O)(CF3COO)6(DMF)3], 3, a Fe(II)-Fe(III)-Fe(III) derivative, and [Fe4(micro3-O)2(micro2-CF3COO)6(CF3COO)2(DMF)4], 4, containing Fe(III) atoms only, which have been characterized by X-ray diffraction methods. Iron(II) chloro- and bromoacetates can be isolated by exchange reactions of iron(II) acetate with chloro- and bromo-substituted acetic acids in moderate to good yields. The stability of iron(II) haloacetates decreases on increasing the atomic weight and the number of halogens on the alpha-carbon atom. The species Fe(CX3COO)2 (X = Cl, 7; Br, 8), in THF solution, slowly convert into [Fe3(micro3-O)(CCl3COO)6(THF)3], 11, or [Fe3(micro3-O)(CBr3COO)6(THF)3][FeBr4], 10, respectively. Likewise, when iron(II) acetate (or trifluoroacetate) is left for several hours in the presence of a variety of haloacetic acids in THF, selective formation of different species, depending on the nature of the starting compound and of the acid employed, is observed. The formation of these products is the result of C-X bond activation (X = Cl, Br) and haloacetato decomposition, which occurs with concomitant oxidation at the metal centers. Carboxylic acid degradation species (CH2XCOOH, CX4, CX3H, CX2H2, X = Cl, Br) have been observed by GC-MS.