Facile and Reversible Formation of Iron(III)–Oxo–Cerium(IV) Adducts from Nonheme Oxoiron(IV) Complexes and Cerium(III)

Abstract

CAN or CeIV(NH4)2(NO3)6 is often used in artificial water oxidation and generally considered to be an outer-sphere oxidant. Herein we report the spectroscopic and crystallographic characterization of [(N4Py)FeIII–O–CeIV(OH2)(NO3)4]+ (3), a complex obtained from the reaction of [(N4Py)FeII(NCMe)]2+ with 2 equiv. CAN or [(N4Py)FeIV=O]2+ (2) with CeIII(NO3)3 in MeCN. Surprisingly, the formation of 3 is reversible, the position of the equilibrium being dependent on the MeCN/water ratio of the solvent. These results suggest that the FeIV and CeIV centers have comparable reduction potentials. Moreover, the equilibrium entails a change in iron spin state, from S = 1 FeIV in 2 to S = 5/2 in 3, which is found to be facile despite the formal spin forbidden nature of this process. This observation suggests that FeIV=O complexes may avail of reaction pathways involving multiple spin states having little or no barrier.

A High‐Valent Manganese(IV)–Oxo–Cerium(IV) Complex and Its Enhanced Oxidizing Reactivity

“…Interestingly, when the rRaman spectra of the reaction solutions of 1-Sc 3+ and 1-Al 3+ with CAN were taken, we found that the bands at 790 and 789 cm -1 completely disappeared (SI, Figures S8b and S9b). Instead, we observed the appearance of a band at 675 cm -1 for 16 O-samples and a band at 645 cm -1 for 18 O-samples (SI, Figures S8b and S9b). Since we have shown above that 1-Ce 4+ exhibits an isotope-sensitive band at 675 cm -1 (vide supra), the results of the rRaman experiments demonstrate unambiguously that 1-Ce 4+ was formed in the substitution reactions of 1-Sc 3+ and 1-Al 3+ with CAN (Scheme 1, reaction c).…”

“…[15] More recently, Que and co-workers reported the spectroscopic and crystallographic characterization of [(N4Py)Fe III -O-Ce IV (OH2)(NO3)4] + (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine), which was obtained from the reaction of [(N4Py)Fe II ] 2+ with 2 equiv of CAN or [(N4Py)Fe IV =O] 2+ with Ce III (NO3)3. [16] However, besides the structural information of the Fe-O-Ce species in nonheme iron systems, no other metal-oxo species binding Ce 4+ ion have been reported yet. Moreover, to the best of our knowledge, the effect of the Ce 4+ ion on the chemical properties of high-valent metal-oxo species has never been discussed previously.…”

“…10 Figure S2). Upon 18 O-substitution using isotopically labeled H2 18 O instead of H2 16 O, the mass peaks at m/z = 820.1, 841.0, and 859.1 shifted to m/z = 822.1, 843.0, and 861.1, respectively, indicating that 1-Ce 4+ contains one oxygen atom derived from water (SI, Figure S2, inset).…”

A tetranuclear CuII2DyIII2 coordination cluster as a Suzuki (C–C) coupling reaction promoter

“…3 In this direction, 3d/4f in situ [4][5][6] or well characterised coordination clusters have recently emerged as sustainable catalytic platforms with advantages in their ease synthesis, good abundance (in spite of belonging to the so-called rare earths) and low cost. 7 Our group has established the efficacy of a series of tetranuclear [M II 2Ln III 2L4(X)2(solv)2] (M = Ni, Co, Cu, Zn, X = Cl, NO3, Ln = Y, Dy, Gd) for domino-electro cyclization and Lewis acid reactions, [8][9][10][11] whereas other groups have, successfully, used them in redox, [12][13][14] co-polymerization 15 and carbon dioxide fixation reactions. 16,17 The metal-promoted Suzuki-Miyaura coupling includes organoboron derivatives and carbon electrophiles, and represents a valuable procedure for a C-C bond formation (Scheme 1).…”

Dinucleating Schiff base ligand in Zn/4f coordination chemistry: synthetic challenges and catalytic activity evaluation

“…The second group of 3d/4f CCs includes paradigms of wellcharacterised pre-catalyst or postulated active species. [24][25][26][27][28][29][30][31][32][33] The advantage of the isolation and use of well-defined species compared to the former set is the possibility to extract mechanistic information by performing controlled experiments and thus shed light in the catalytic nature of the 3d/4f PCCs. Moreover, this approach allows to fine tune the reaction conditions (i.e.…”