Manipulating Magnetism: Ru₂⁵⁺ Paddlewheels Devoid of Axial Interactions

Abstract

Variable-temperature magnetic and structural data of two pairs of diruthenium isomers, one pair having an axial ligand and the formula Ru2(DArF)4Cl (where DArF is the anion of a diarylformamidine isomer and Ar = p-anisyl or m-anisyl) and the other one being essentially identical but devoid of axial ligands and having the formula [Ru2(DArF)4]BF4, show that the axial ligand has a significant effect on the electronic structure of the diruthenium unit. Variable temperature crystallographic and magnetic data as well as density functional theory calculations unequivocally demonstrate the occurrence of π interactions between the p orbitals of the chlorine ligand and the π* orbitals in the Ru2(5+) units. The magnetic and structural data are consistent with the existence of combined ligand σ/metal σ and ligand pπ/metal-dπ interactions. Electron paramagnetic resonance data show unambiguously that the unpaired electrons are in metal-based molecular orbitals.

Synthesis, Crystal Structure, and Magnetic Properties of Amidate and Carboxylate Dimers of Ruthenium

“…The higher donor character of the amidate ligands with respect to the carboxylate groups produces a higher electronic density on the ruthenium atoms giving a larger Ru-Ru distance. This is in accordance with the higher Ru-Ru distance found in the [Ru2(µ-N-N)4]Cl compounds where N-N = formamidinate [20][21][22][23]. There are not significant differences in these distances with the change of the nature of the halide axial ligand.…”

Synthesis, Structure and Magnetic and Electrochmical Properties of Tetrakis(benzamidato)diruthenium(II,III) Tetrafluoroborate

“…The SOMO-LUMO and highest-occupied MO (HOMO)-LUMO gaps at α and β orbitals are estimated as 4.09 and 2.57 eV, respectively. 4 ]BF 4 is a unique complex with an S = 1/2 ground state due to the π* 3 electronic configuration, where the δ* orbital is energetically higher than the π* orbitals in the case of no anti-bonding π-type interactions with axial ligands having a π character, such as Cl − ions [10].…”

“…The spin state of S = 3/2 has also been thought to be common for the diruthenium(II,III) complex with diarylformamidinate (DArF − ) bridges having an N,N-donor set, the chemical structure of which is shown in Scheme 1a [1,[6][7][8], although a spin cross-over behavior was reported for [Ru2(DArF)4Cl] (Ar = p-methoxyphenyl group) [9]. Recently, [Ru2(DArF)4]BF4 (Ar = p-methoxyphenyl or m-methoxyphenyl group) obtained by the removal of the axial chloride ion from [Ru2(DArF)4Cl] was reported to show a singlet ground state (S = 1/2) [10]. Such spin state change from S = 3/2 to S = 1/2 has not been reported on the removal of the axial halogenide ligand from [Ru2(O2CR)4X].…”

Synthesis, structures, and properties of lantern-type dinuclear ruthenium(II,III) complexes cis-[Ru2{3,5-(CF3)2-pf}2(O2CMe)2Cl] and [Ru2{3,5-(CF3)2-pf}3(O2CMe)Cl], 3,5-(CF3)2-pf−=N,N′-bis[3,5-bis(trifluoromethyl)phenyl]formamidinate anion

“…60 cm À1 ) [3][4][5][6]. N,N 0 -Bis(alkylphenyl, alkoxyphenyl or chlorophenyl)formamidinate anions (R m -pf À ) work as bridging ligands with or without carboxylate ions (R 0 CO 2 À ) for ruthenium ions to give lantern-type dinuclear complexes, [Ru 2 (R m -pf)(O 2 CR 0 ) 3 Cl], [Ru 2 (R m -pf) 2 (O 2 CR 0 ) 2 Cl], [Ru 2 (R m -pf) 3 (O 2 CR 0 )Cl], and [Ru 2 (R m -pf) 4 Cl] [3,[7][8][9]. In the cases of [Ru 2 (R m -pf) 2 (O 2 CR 0 ) 2 Cl], their electronic structure were also reported to be r 2 p 4 d 2 (p ⁄ d ⁄ ) 3 , which can be changed when the other axial ligand takes place of the chloride ligand [10][11][12][13].…”