Synthesis and electrochemical properties of organometallic macrocyclic crown ethers containing redox-active tetrahedral Mo2Fe(μ3-S) cluster cores. Crystal structures of [Mo2Fe(μ3-S)(CO)7][η5-C5H4CH2(CH2OCH2)n CH2C5H4-η5] (n=1–3)

The self-assembly cyclization reactions of the ether chain-bridged dicyclopentadienyl Mo/Na salts [NaMo(CO)3]2[η5-C5H4CH2(CH2OCH2)nCH2C5H4-η5] (Ia-d, n=1–4) with the same chain-bridged dicyclopentadienyl double clusters [MoCoFe(μ3-S)(CO)8]2[η5-C5H4CH2(CH2OCH2)nCH2C5H4-η5] (Iia–d, n=1–4) have been found, depending on the lengths of the bridged ether chains in starting materials I and II, to give several different types of novel organometallic macrocyclic crown ethers. While reaction of the Mo/Na salts (I, n=1, 4) with double clusters (II, n=1, 4) produced single Mo2Fe(μ3-S) cluster crown ethers [Mo2Fe(μ3-S)(CO)7][η5-C5H4CH2(CH2OCH2)n CH2C5H4-η5] (IIIa, n=1; IIId, n=4), the Mo/Na salts (I, n=2, 3) reacted with double clusters (II, n=2, 3) to afford single, double and triple Mo2Fe(μ3-S) cluster crown ethers [Mo2Fe(μ3-S)(CO)7]m[η5-C5H4CH2(CH2OCH2)nCH2 C5H4-η5]m (IIIb, n=2, m=1; IIIc, n=3, m=1; IVb, n=2, m=2; IVc, n=3, m=2; Vb, n=2, m=3; Vc, n=3, m=3), respectively. While structures of IIIa–d, IVb,c and Vb,c were characterized fully by elemental analyses, IR, 1H-NMR and FAB-MS spectrocopies, those of IIIa–c were further confirmed by X-ray diffraction techniques. In addition, the electrochemical properties of IIIa–d, IVb,c and Vb,c have been studied using cyclic voltammetry.