Exploring the Role of Carbonate in the Formation of an Organomanganese Tetramer

N-Oxide Coordination to Mn(III) Chloride

We report on the synthesis and characterization of Mn(III) chloride (MnIIICl3) complexes coordinated with N-oxide ylide ligands, namely trimethyl-N-oxide (Me3NO) and pyridine-N-oxide (PyNO). The compounds are reactive and, while isolable in the solid-state at room temperature, readily decompose into Mn(II). For example, "[MnIIICl3(ONMe3)n]" decomposes into the 2D polymeric network compound complex salt [MnII(µ-Cl)3MnII(µ-ONMe3)]n[MnII(µ-Cl)3]n·(Me3NO·HCl)3n (4). The reaction of MnIIICl3 with PyNO forms varied Mn(III) compounds with PyNO coordination and these react with hexamethylbenzene (HMB) to form the chlorinated organic product 1-cloromethyl-2,3,4,5,6-pentamethylbenzene (8). In contrast to N-oxide coordination to Mn(III), the reaction between [MnIIICl3(OPPh3)2] and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) resulted in electron transfer-forming d5 manganate of the [TEMPO] cation instead of TEMPO-Mn(III) adducts. The reactivity affected by N-oxide coordination is discussed through comparisons with other L-MnIIICl3 complexes within the context of reduction potential.

A hemilabile manganese(i)–phenol complex and its coordination induced O–H bond weakening

Synthesis and characterization of [(HPO)(PO)Mn(CO)₂ (^H1), a phenol bound first-row transition metal complex, is reported. Thermochemical analysis of ^H1 indicated the presence of coordination induced O–H bond weakening.

Bisphosphine phenol and phenolate complexes of Mn(i): manganese(i) catalyzed Tishchenko reaction

We synthesized new organomanganese complexes using the phenolic “pincer” type ligand H-POP.

Photochemical Water-Splitting with Organomanganese Complexes

Certain organometallic chromophores with water-derived ligands, such as the known [Mn(CO)₃(μ₃-OH)]₄ (1) tetramer, drew our attention as possible platforms to study water-splitting reactions. Herein, we investigate the UV irradiation of various tricarbonyl organomanganese complexes, including 1, and demonstrate that dihydrogen, CO, and hydrogen peroxide form as products in a photochemical water-splitting decomposition reaction. The organic and manganese-containing side products are also characterized. Labeling studies with ¹⁸O-1 suggest that the source of oxygen atoms in H₂O₂ originates from free water that interacts with 1 after photochemical dissociation of CO (1-CO) constituting the oxidative half-reaction of water splitting mediated by 1. Hydrogen production from 1 is the result of several different processes, one of which involves the protons derived from the hydroxido ligands in 1 constituting the reductive half-reaction of water splitting mediated by 1. Other processes that generate H₂ are also operative and are described. Collectively the results from the photochemical decomposition of 1 provide an opportunity to propose a mechanism, and it is discussed within the context of developing new strategies for water-splitting reactions with organomanganese complexes.