Different delocalized ranges in mixed valence cyanido-metal-bridged Fe-Ru-Fe complexes controlled by terminal ligand substitution modification

• Published in: Dalton transactions : an international journal of inorganic chemistry 2023-11, Vol.52 (45), p.16858-16869
• Main Authors: Zeng, Chen, Xu, Qing-Dou, Liu, Xiao-Lin, Hu, Sheng-Min, Wu, Xin-Tao, Sheng, Tian-Lu
• Format: Article
• Language: English
• Subjects: Charge transfer; Crystallography; Energy levels; Ethane; Iron; Mossbauer spectroscopy; Oxidation
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d3dt02208k

In order to investigate the properties of metal to metal charge transfer (MMCT) influenced by the relative energy level between the bridging unit and the terminal unit, two groups of heterotrimetallic cyanido-metal-bridged complexes, trans -[Cp(dppe)Fe-CN-Ru(MeOpy) 4 -NC-Fe(dppe)Cp][X] n ( 1[X] n ; n = 2, 3, or 4; X = PF 6 or BF 4 ) (Cp = cyclopentadiene, dppe = 1,2-bis(diphenylphosphino)ethane, MeOpy = 4-methoxypyridine) and [Cp*(dppe)Fe-CN-Ru(MeOpy) 4 -NC-Fe(dppe)Cp*] [X] n ( 2[X] n ; Cp* = 1,2,3,4,5-pentamethylcyclopentadiene; n = 2, 3, or 4; X = PF 6 or BF 4 ) were synthesized and fully characterized. The crystallography data suggest different oxidation sites in the ground state for one-electron oxidation products 1 3+ and 2 3+ , and the electrochemical and Mössbauer spectra suggest that in the one-electron oxidation compounds 1 3+ , the charge is delocalized all along the trimetal backbone Fe-Ru-Fe, while in 2 3+ , the charge is rather delocalized between the two metal parts Fe-Ru. Further oxidation of N 3+ gives N 4+ ( N = 1 or 2), during which a spin transfer towards the terminal units is observed in both series. A substituent change from Cp to Cp* in cyanidometal bridged Fe-Ru-Fe complexes makes the one-electron oxidation products not only show a redox site change from Ru to Fe, but also exhibit a delocalization range change from Fe-Ru-Fe to Fe-Ru.