Stable and Highly Persistent Quinoxaline-Centered Metalloorganic Radical Anions: Preparation, Structural, Spectroscopic, and Computational Investigations

Heavy Alkali Metal Manganate Complexes: Synthesis, Structures and Solvent-Induced Dissociation Effects

Rare examples of heavier alkali metal manganates [{(AM)Mn(CH₂ SiMe₃ )(N^'Ar )₂ }_∞ ] (AM=K, Rb, or Cs) [N^'Ar =N(SiMe₃ )(Dipp), where Dipp=2,6-iPr₂ -C₆ H₃ ] have been synthesised with the Rb and Cs examples crystallographically characterised. These heaviest manganates crystallise as polymeric zig-zag chains propagated by AM⋅⋅⋅π-arene interactions. Key to their preparation is to avoid Lewis base donor solvents. In contrast, using multidentate nitrogen donors encourages ligand scrambling leading to redistribution of these bimetallic manganate compounds into their corresponding homometallic species as witnessed for the complete Li - Cs series. Adding to the few known crystallographically characterised unsolvated and solvated rubidium and caesium s-block metal amides, six new derivatives ([{AM(N^'Ar )}_∞ ], [{AM(N^'Ar )⋅TMEDA}_∞ ], and [{AM(N^'Ar )⋅PMDETA}_∞ ] where AM=Rb or Cs) have been structurally authenticated. Utilising monodentate diethyl ether as a donor, it was also possible to isolate and crystallographically characterise sodium manganate [(Et₂ O)₂ Na(ⁿ Bu)Mn[(N^'Ar )₂ ], a monomeric, dinuclear structure prevented from aggregating by two blocking ether ligands bound to sodium.

A redox-active Mn(0) dicarbene metalloradical

A rare redox-active Mn(0) dicarbene anion with solvent-dependent electrochemical behaviour has been synthesized and thoroughly characterized.

Mechanisms for CO production from CO2 using reduced rhenium tricarbonyl catalysts

The chemical conversion of CO(2) has been studied by numerous experimental groups. Particularly the use of rhenium tricarbonyl-based molecular catalysts has attracted interest owing to their ability to absorb light, store redox equivalents, and convert CO(2) into higher-energy products. The mechanism by which these catalysts mediate reduction, particularly to CO and HCOO(-), is poorly understood, and studies aimed at elucidating the reaction pathway have likely been hindered by the large number of species present in solution. Herein the mechanism for carbon monoxide production using rhenium tricarbonyl catalysts has been investigated using density functional theory. The investigation presented proceeds from the experimental work of Meyer's group (J. Chem. Soc., Chem. Commun.1985, 1414-1416) in DMSO and Fujita's group (J. Am. Chem. Soc.2003, 125, 11976-11987) in dry DMF. The latter work with a simplified reaction mixture, one that removes the photo-induced reduction step with a sacrificial donor, is used for validation of the proposed mechanism, which involves formation of a rhenium carboxylate dimer, [Re(dmb)(CO)(3)](2)(OCO), where dmb = 4,4'-dimethyl-2,2'-bipyridine. CO(2) insertion into this species, and subsequent rearrangement, is proposed to yield CO and the carbonate-bridged [Re(dmb)(CO)(3)](2)(OCO(2)). Structures and energies for the proposed reaction path are presented and compared to previously published experimental observations.