Two new octahedral rhenium cluster complexes, [Re6S7O(3,5-Me(2)PzH)(6)]Br(2)(.)3,5-Me(2)PzH (1) and [Re6Se7O(3,5-Me(2)PzH)(6)]Br(2)(.)3,5-Me(2)PzH (2), with the organic ligand 3,5-dimethylpyrazole (3,5-Me(2)PzH), have been synthesised by reaction of rhenium chalcobromides Cs-3[Re-6(mu(3)-Q(7)Br)Br-6] (Q = S, Se) with molten dimethylpyrazole. During the reaction, all six apical bromine ligands of the cluster complexes are substituted by the organic ligand, which is coordinated through the aromatic nitrogen atom N2. Additionally, the inner hgand mu(3)-Br in the cluster core [Re-6(mu(3)-Q(7)O)](3+) is substituted by oxygen, giving cluster cores [Re-6(mu(3)-Q(7)O)](2+) with mixed chalcogen/oxygen ligands. Compounds 1 and 2 have been characterised by single-crystal X-ray diffraction analysis. They are isostructural and crystallise with four formula units in the unit cell. Absorption spectra and luminescence characteristics of these two cluster compounds have been investigated in methanol. Absorption starts below 400 rim. For both compounds, broad emissions were found. The fluorescence decays of the two compounds follow a diexponential decay behaviour. The main fluorescence intensity decays have longer fluorescence lifetimes of 3.07 +/- 0.03 (1) and 3.96 +/- 0.02 mus (2). Studying the thermal stability of both compounds in vacuo showed that the release of 3,5-dimethylpyrazole ligands begins near 200 degreesC, and decomposition, with the removal of 7 molecules of 3,5-Me2PzH, is complete at 330 degreesC. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
