title: Redox flexibility of iron complexes supported by sulfur-based tris(o-methylenethiophenolato)amine relative to its tripodal oxygen-based congener.
abstract: Tripodal ligands designed to generate a local C3 symmetry have resulted in novel types of metal complexes that feature unusual bonding and electronic properties. However, most complexes reported to date are characterised by strong field ligands that enforce low or intermediate-spin states for the metal centres. Moreover, anionic sulfur-based tripodal ligands are particularly scarce due to their challenging synthesis. In this context, we herein report the synthesis, spectral characterization, structural, and electronic properties of an iron complex supported by the tripodal, trianionic ligand [N(CH2ArS)3](3-) as the trigonal-bipyramidal complexes [Fe{N(CH2ArS)3}(X)] ((X), X = DMSO, THF). The solid-state structures reveal local C3v symmetry around the Fe(3+) ions, while electron spin resonance measurements established a high-spin state (S = 5/2). Electrochemical studies demonstrate the redox flexibility of the FeS3 fragment by direct comparison with the oxygen-based analogue N(CH2ArOH)3, which displays an irreversible reduction; in contrast, (THF) has a reversible Fe(3+)/Fe(2+) redox process at -0.83 V (relative to the ferrocenium/ferrocene redox couple). The high spin and redox properties of (THF) are attributable to the weak ligand field provided by the NS3 fragment, as confirmed by the electronic structure calculated by density functional theory, which reveals substantial electronic delocalisation and covalency of the Fe-S bonds in (X).
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, CU, México DF, 04510, México. joseivan@unam.mx.
authors.forename: Alexander
authors.initials: A
authors.lastname: Mondragón
authors.affiliation: Departament de Química Inorgànica and Institut de Química Teòrica i Computacional, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
authors.forename: Paulina R
authors.initials: PR
authors.lastname: Martínez-Alanis
authors.affiliation: Departament de Química Inorgànica and Institut de Química Teòrica i Computacional, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Aullón
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, CU, México DF, 04510, México. joseivan@unam.mx.
authors.forename: Simón
authors.initials: S
authors.lastname: Hernández-Ortega
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, CU, México DF, 04510, México. joseivan@unam.mx.
authors.forename: Elvis
authors.initials: E
authors.lastname: Robles-Marín
authors.affiliation: Facultad de Química, División de Estudios de Posgrado, Universidad Nacional Autónoma de México, Ciudad Universitaria, México DF, 04510, México.
authors.forename: Marcos
authors.initials: M
authors.lastname: Flores-Alamo
authors.affiliation: Facultad de Química, División de Estudios de Posgrado, Universidad Nacional Autónoma de México, Ciudad Universitaria, México DF, 04510, México.
authors.forename: Víctor M
authors.initials: VM
authors.lastname: Ugalde-Saldívar
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, CU, México DF, 04510, México. joseivan@unam.mx.
authors.forename: Ivan
authors.initials: I
authors.lastname: Castillo