An iron-sulfur-tin cluster with amino-ligands and its reactions with thiols

The dinuclear complex Fe2(mu2-eta2-S2)(CO)6 (1) has been reacted with the bis(amino)stannylene Sn(mu-Nt-Bu)2SiMe2 (2) to form the new 1:1 complex Me2Si(mu-Nt-Bu)2SnFe2(mu3-S)2(CO)6 (4). The 'double-star'shape of its Fe2S2Sn central core (X-ray structure analysis, multinuclear NMR) contains a tetracoordinated tin atom, which provides a spirocyclic connection between the Fe2S2 butterfly and the four-membered SnN2Si cycle. The reaction can thus be described as an insertion of the divalent tin into the sulphur-sulphur bond of the Fe2(mu2-eta2-S2)(CO)6 precursor. All distances and angles in 4 are in accordance with tin being in the formal oxidation state +4. The Sn-N bonds in this cluster can serve as excellent targets for the subsequent addition of thiols (sulphanes). Indeed, these bonds are highly reactive and when HS(CH2)2SH is allowed to react with 4, the cluster is destroyed and the spiro-cyclic tin sulphide Sn[S2(CH2)2]2 is the only isolable reaction product. If HS(CH2)2SH is replaced by Me3Si(CH2)2SH, the 1:1 adduct Me2Si(mu-Nt-Bu)[mu-N(H)t- Bu]Sn{S(CH2)2SiMe3}(mu3-S)2Fe2(CO)6 (6a) is isolated. This new cluster contains a five-coordinate tin atom (three S and two N donors) and has several functional groups (X-ray structure analysis, NMR). The proton of the thiol reagent Me3Si(CH2)2SH has migrated to one of the nitrogen atoms as a result of selective S-H addition across an Sn-N bond, while the Fe2S2Sn core remains intact. To the best of our knowledge, no other tin compound displaying two nitrogen and three sulphur ligands has been structurally described before.