Syntheses and structures of two new M6L18(N3)a6 cluster-unit based compounds:: Cs4Re6S8(N3)6•H2O and Na2Mo6Br8(N3)6•2H2O

The two new cluster compounds, Cs4Re6S8(N-3)(6).H2O (1) and Na2Mo6Br8(N-3)(6).2H(2)O (2), have been prepared via solution chemistry route, starting from the Cs4Re6S8Br6-CsBr and Mo6Br12 precursors synthesized by solid state chemistry techniques, and structurally characterized (crystal data: Cs4Re6S8(N-3)(6).H2O (1): Orthorhombic, space group Pnam, a = 10.0651(1) Angstrom, b = 15.8856(2) Angstrom, c = 20.1714(3) Angstrom, V = 3225.2(7) Angstrom(3), Z = 4, d(calc) = 4.48 g cm(-3), mu = 27.43 mm(-1); Na2Mo6Br8(N-3)(6).2H(2)O (2): Orthorhombic, space group Ibam, a = 11.5643(3) Angstrom, b = 14.3959(5) Angstrom, c = 17.0340(7) Angstrom, V = 2835.8(2) Angstrom(3), Z = 4, d(calc) = 3.63 g cm(-3), mu = 13.91 mm(-1)). Their structures revealed that in both cases, the M6L8i cluster core remains unchanged in the starting and final compounds whereas the bromine apical ligands (Br-a) are substituted by N-3 azide groups leading to M6L8i(N-3)(6)(a) cluster unit. The new Cs4Re6S8(N-3)(6).H2O is the first example of a compound containing an octahedral rhenium cluster coordinated to azide groups. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.