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.