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Unusual Syntheses, Structures, and Electronic Properties of Compounds Containing Ternary, T3-Type Supertetrahedral M/Sn/S Anions [M5Sn(μ3-S)4(SnS4)4]10- (M = Zn, Co)

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posted on 08.08.2005 by Christian Zimmermann, Christopher E. Anson, Florian Weigend, Rodolphe Clérac, Stefanie Dehnen
A recently discovered series of quaternary compounds of the general type [Km(ROH)n][MxSnySez] (R = H, Me), containing ternary anions with [SnSe4]4--coordinated transition metal centers (M = Co, Mn, Zn, Cd, Hg) has now been extended by the synthesis and characterization of the two ortho-thiostannate-coordinated species, [Na10(H2O)32][M5Sn(μ3-S)4(SnS4)4]·2H2O (M = Zn (1), Co (2)). The central structural motifs of compounds 1 and 2 are highly charged [M5Sn(μ3-S)4(SnS4)4]10- anions, being the first T3-type supertetrahedral ternary anions reported to date. The exposure of single crystals of 2 to a dynamic vacuum for several hours resulted in the reversible formation of a partially dehydrated, but still monocrystalline material of the composition [Na10(H2O)6][Co5Sn(μ3-S)4(SnS4)4] (3). The loss of 28 of the 34 water molecules only slightly affects the internal structure of the ternary anion in 3 and leads to a significant compacting of the crystal structure with closer linkage of the [Co5Sn5S20]10- cluster units via the Na+ cations. Magnetic measurements on 3 show that the ground state of the Co/Sn/S cluster is S = 1/2, indicating a significant antiferromagnetic coupling between the Co centers, which has also been rationalized by DFT investigations of the electronic situation in the ternary subunits of 13.