Unusual syntheses, structures, and electronic properties of compounds containing ternary, T3-type supertetrahedral M/Sn/S anions [M 5Sn(μ3-S)4(SnS4) 4]10- (M = Zn, Co)

Article abstract of DOI:10.1021/ic050466o

A recently discovered series of quaternary compounds of the general type [K_m(ROH)_n][M_xSn_ySe_z] (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][M ₅Sn(μ₃-S)₄(SnS₄) ₄]·2H₂O (M = Zn (1), Co (2)). The central structural motifs of compounds 1 and 2 are highly charged [M₅Sn(μ ₃-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-(SnS ₄)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 1-3.