Self-Assembly and Redox Modulation of the Cavity Size of an Unusual Rectangular Iron Thiolate Aryldiisocyanide Metallocyclophane

The decarbonylation reaction of ferric carbonyl dicationic [Cp2Fe2(μ-SEt)2(CO)2](BF4)2 [1(BF4)2] carried out in refluxing acetonitrile affords a binuclear iron–sulfur core complex [Cp2Fe2(μ-SEt)2(CH3CN)2](BF4)2 [2(BF4)2] containing two acetonitrile coordinated ligands. The treatment of 2(BF4)2 with 2 equiv of the 1,4-diisocyanobenzene (1,4-CNC6H4NC) results in the formation of the diisocyanide complex [Cp2Fe2(μ-SEt)2(1,4-CNC6H4NC)2](BF4)2 [3(BF4)2]. The rectangular tetranuclear iron thiolate aryldiisocyanide metallocyclophane complex [Cp4Fe4(μ-SEt)4(μ-1,4-CNC6H4NC)2](BF4)4 [4(BF4)4] has been synthesized by a self-assembly reaction between equimolar amounts of 2(BF4)2 and 1,4-diisocyanobenzene or by a stepwise route involving mixing of a 1:1 molar ratio of complexes 2(BF4)2 and 3(BF4)2. Chemical reduction of 4(BF4)4 by KC8 was observed to produce the reduction product 4(BF4)2. The spectroscopic and electrochemical properties of the iron–sulfur core complexes 1(PF6)2, 3(BF4)2, 4(BF4)4, and 4(BF4)2 were determined. Finally, differences between the redox control cavities of rectangular tetranuclear iron thiolate aryldiisocyanide complexes are revealed by a comparison of the X-ray crystallographically determined structures of complexes 4(BF4)4 and 4(BF4)2.