A mesoionic carbene complex of manganese in five oxidation states

Abstract

Reaction between a carbazole-based mesoionic carbene ligand and manganese(II) iodide results in the formation of a rare air stable manganese(IV) complex after aerobic workup. Cyclic voltammetry reveals the complex to...

Zinc(II) Complexes with Triplet Charge-Transfer Excited States Enabling Energy-Transfer Catalysis, Photoinduced Electron Transfer, and Upconversion

“…The ILCT states of our Zn II complexes complement the different types of photoactive excited states reported recently for first-row and other Earth-abundant transition-metal complexes, 28 which includes the classical MLCT states for d 6 complexes (Cr 0 , Mn I , Fe II , Co III ), 19 , 24 , 25 , 115 − 117 square-planar d 8 compounds (Ni II ) 26 , 118 and four-coordinate d 10 complexes (Cu I ), 3 , 78 ligand-to-metal charge-transfer (LMCT) states for Ti IV , Zr IV , 119 , 120 Mn IV , Fe III and Co III , 121 − 126 121 − 126 metal-centered (MC) states for V III , Cr III and Co III , 127 − 132 as well as ligand-to-ligand charge-transfer (LLCT) excited states for two-coordinate Cu I complexes. 29 − 33 Given these findings, it seems reasonable to conclude that Zn II complexes with charge-transfer and triplet excited states would perhaps deserve greater attention in future studies aiming to discover new photophysics and photochemistry in first-row transition-metal complexes.…”

The Full d3–d5 Redox Series of Mononuclear Manganese Complexes: Geometries and Electronic Structures of [Mn(dgpy)2]n+

“… − The highest potentials are achieved by pyridine and pyrazol donors, − while strong donors such as guanidines or carbenes and anionic donors such as guanidinates, hydrazides, amides, or azides lower the potential appreciably , (Chart ). Six carbene donors or four carbene donors with two amides furnish E (Mn IV/III ) potentials as low as −0.71 and −0.55 V, respectively. , …”

“…Six carbene donors or four carbene donors with two amides furnish E(Mn IV/III ) potentials as low as −0.71 and −0.55 V, respectively. 15,16 None of the reported manganese complexes with [MnN 6 ] coordination were structurally characterized in both the +III and +IV oxidation states and certainly not in the three oxidation states +II, +III, and +IV. Consequently, only limited information is available on molecular [MnN 6 ] complexes, while the full series of solid manganese oxides MnO (manganosite), Mn 2 O 3 (bixbyite), and MnO 2 (pyrolusite) represents standard textbook knowledge.…”

Manganese(iii) complexes stabilized with N-heterocyclic carbene ligands for alcohol oxidation catalysis

“…19 Even with potentially harder mesoionic carbenes (MICs) as a subclass of NHCs, [20][21][22] only a single example of a Mn(III) complex has been reported so far. 23 This underrepresentation is remarkable, when considering the Fig. 1 (a) Examples of higher-valent Mn complexes with catalytic activity in oxidation reactions (ref.…”

“…19 Even with potentially harder mesoionic carbenes (MICs) as a subclass of NHCs, 20–22 only a single example of a Mn( iii ) complex has been reported so far. 23 This underrepresentation is remarkable, when considering the strong σ-donor character of NHCs in general and of MICs in particular, and their beneficial effects in a variety of catalytic oxidation reactions. 24–26…”