Reactivity of Labile Triosmium Complexes, [Os3(CO)10(MeCN)2] and [Os3(CO)10(µ-H)2] with Tetraethylthiuram Disulfide (Disulfiram)

Abstract

Reactions of the anti-alcohol drug disulfiram (tetraethylthiuram disulphide = Et₄TDS) with low valent triosmium complexes are described. Room temperature reaction with [Os₃(CO)₁₀(MeCN)₂], affords three new open polynuclear clusters, [Os₃(CO)₁₀(S₂CNEt₂)₂] (1), [Os₄(CO)₁₂{µ₃-η¹(C),κ²(O,O)-CO₂}(S₂CNEt₂)(µ-S₂CNEt₂)] (2) and [Os₃(CO)₉(µ₃-SCNEt₂){µ-SC(O)NEt₂}] (3) together with the known mononuclear complex cis-[Os(CO)₂(S₂CNEt₂)₂] (4). All result from oxidative-addition of disulfiram to the triosmium centre, with 2 also capturing CO₂, while cluster 3 has undergone further C–S bond scission and partial oxidation of one of the generated thiocarboxamide ligands. With [Os₃(CO)₁₀(µ-H)₂], complexes 1 and 4 are also formed along with previously reported [Os₃(CO)₁₀(µ-S₂CNEt₂)(µ-H)] (5), [Os₃(CO)₉(µ₃-S₂CNEt₂)(µ-H)] (6), and the new cluster, [Os₃(CO)₉(µ-S₂CNEt₂)(µ-H)] (8), which is an isomer of 6. The product distribution is rationalized by completing pathways following the oxidative-addition of disulfiram. Thus, reductive-elimination of H₂ affords 1, which in turn converts to 4, while reductive-elimination of the (unstable) dithiocarbamic acid, Et₂NCS₂H, leads to the formation of 5, which can further lose CO to afford isomers 6 and 8. Heating disulfiram with [Os₃(CO)₁₂] at 110 °C predominantly affords 4, together with smaller amounts of the novel trithiocarbamate complex, cis-[Os(CO)₂(S₂CNEt₂)(S₃CNEt₂)] (9). All the compounds have been characterized by elemental analysis, IR and ¹H NMR spectroscopy, together with single crystal X-ray diffraction analysis of six molecules.