A Phosphorus Analogue of Bis(η4‐cyclobutadiene)iron(0)

P makes it possible : The convenient oxidative synthesis of the 16‐electron organophosphorus iron sandwich complex [Fe(η⁴‐P₂C₂tBu₂)₂] (see structure) suggests that the elusive all‐carbon complex [Fe(η⁴‐C₄H₄)₂] is a viable synthetic target.

     

Titelbild: A Phosphorus Analogue of Bis(η4‐cyclobutadiene)iron(0) (Angew. Chem. 17/2009)

Ein Phosphoranalogon des Komplexes Bis(η⁴‐cyclobutadien)eisen(0) wird von K. Lammertsma et al. in ihrer Zuschrift auf S. 3150 ff. vorgestellt. Im Hintergrund des Titelbilds posiert John Montagu (1718–1792), 4th Earl of Sandwich und Erster Lord der Admiralität, der es sich sicherlich nicht hätte träumen lassen, dass eines Tages eine wichtige Klasse von Organometallverbindungen nach ihm benannt werden würde. Die Synthese von [Fe(P₂C₂tBu₂)₂] belegt, dass die Sandwich‐Komplexe immer noch ein aktuelles Forschungsgebiet sind.

     

Ligand Design for Site‐Selective Metal Coordination: Synthesis of Transition‐Metal Complexes with η6‐Coordination of the Central Ring of Anthracene

A polycyclic aromatic ligand for site‐selective metal coordination was designed by using DFT calculations. The computational prediction was confirmed by experiments: 2,3,6,7‐tetramethoxy‐9,10‐dimethylanthracene initially reacts with [(C₅H₅)Ru(MeCN)₃]BF₄ to give the kinetic product with a [(C₅H₅)Ru]⁺ fragment coordinated at the terminal ring, which is then transformed into the thermodynamic product with coordination through the central ring. These isomeric complexes have markedly different UV/Vis spectra, which was explained by analysis of the frontier orbitals. At the same time, the calculations suggest that electrostatic interactions are mainly responsible for the site selectivity of the coordination.