Intriguing I₂ Reduction in the Iodide for Chloride Ligand Substitution at a Ru(II) Complex: Role of Mixed Trihalides in the Redox Mechanism

Abstract

The compound [Ru(CN(t)Bu)4(Cl)2], 1, reacts with I2, yielding the halogen-bonded (XB) 1D species {[Ru(CN(t)Bu)4(I)2]·I2}n, (2·I2)n, whose building block contains I(-) ligands in place of Cl(-) ligands, even though no suitable redox agent is present in solution. Some isolated solid-state intermediates, such as {[Ru(CN(t)Bu)4(Cl)2]·2I2}n, (1·2I2)n, and {[Ru(CN(t)Bu)4(Cl)(I)]·3I2}n, (3·3I2)n, indicate the stepwise substitution of the two trans-halide ligands in 1, showing that end-on-coordinated trihalides play a key role in the process. In particular, the formation of ClI2(-) triggers electron transfer, possibly followed by an inverted coordination of the triatomic species through the external iodine atom. This allows I-Cl separation, as corroborated by Raman spectra. The process through XB intermediates corresponds to reduction of one iodine atom combined with the oxidation of one coordinated chloride ligand to give the corresponding zerovalent atom of I-Cl. This redox process, explored by density functional theory calculations (B97D/6-31+G(d,p)/SDD (for I and Ru atoms)), is apparently counterintuitive with respect to the known behavior of the corresponding free halogen systems, which favor iodide oxidation by Cl2. On the other hand, similar energy barriers are found for the metal-assisted process and require a supply of energy to be passed. In this respect, the control of the temperature is fundamental in combination with the favorable crystallizations of the various solid-state products. As an important conclusion, trihalogens, as XB adducts, are not static in nature but are able to undergo dynamic inner electron transfers consistently with implicit redox chemistry.

The atomic level mechanism of white phosphorous demolition by di-iodine

“…Previously, we have already addressed some other peculiar behavior of XB adducts formed at a metal center upon the I 2 addition to a chloride ligand, which is intriguingly substituted by an in situ formed less electronegative iodide. 27,28 Also in this case, the key information was extracted by the computational monitoring of the system's evolution involving a XB dynamism. The general electronic underpinnings of the latter are briefly summarized in the next section.…”

“…one iodide from the hetero-diatomic I-Cl, which was experimentally detected by Raman spectra. 28 To generalize the expected trends of electronic redistribution in a linear XB system, we emphasize the qualitative implications of the generic HOMO in Scheme 1. 27 In the latter, the sp hybridization of the central atom depends on the lateral donor power.…”

Overcoming the Inertness of Iridium(III) in a Facile Single‐Crystal to Single‐Crystal Reaction of Iodine Vapor with a Cyclometalated Chloride Monomer

“…Thus, the crystal packing peculiarities of 1 result in formation of two different spatially separated chemical species Ir( L ) 2 ‐ClI 2 and Ir( L ) 2 ‐Cl(I 2 ) 2 inside the same crystal. The latter molecule is less stable than the former and, hence, readily changes the monodentate ligand to iodide …”

“…Thus, the crystal packing peculiarities of 1 result in formation of two different spatially separated chemical species Ir(L) 2 -ClI 2 and Ir(L) 2 -Cl(I 2 ) 2 inside the same crystal.T he latter molecule is less stable than the former and, hence, readily changes the monodentate ligand to iodide. [31] In summary,w ehave synthesized and studied the reactivity of at rigonal-bipyramidalp henanthroimidazole-based cyclometalated iridium(III) chloride. We predicted, and then undoubtedly confirmed, the monomeric structure of this complex by Xray diffraction analysis.…”

Extended Assemblies of Ru(bpy)(CO)2X2 (X = Cl, Br, I) Molecules Linked by 1,4-Diiodotetrafluoro-Benzene (DITFB) Halogen Bond Donors

“…This means that the M-X•••X angle in a halogen bonded M-X•••X-R system is typically ranging between 90 • and 150 • , depending on the nature of the metal center [13,30,31]. By using bidentate halogen bond donors, such as I 2 , it is possible to link metal complexes together to form non-covalent metallopolymers [14,30,31,[37][38][39][40][41][42][43][44][45][46][47]. However, I 2 is not necessarily the most desirable linking unit due to its redox behavior and its impact on the metal complex [45,47].…”