Phenylimido complexes of rhenium: fluorine substituents provide protection, reactivity, and solubility

Abstract

Reactions of [Re(NPhF)Cl₃(PPh₃)₂] ({NPhF}²⁻ = p-fluorophenylimide) with a variety of alkyl and aryl isocyanides have been studied. Different reactivity patterns and products have been obtained depending on the steric and electronic properties of the individual ligands. This involves the formation of 1 : 1 and 1 : 2 exchange products of Re(V) with the general formulae mer-[Re(NPhF)Cl₃(PPh₃)(isocyanide)] and cis- or trans-[Re(NPhF)Cl₃(isocyanide)₂]. The stability of the obtained products is correlated with the substitution pattern of the isocyanide ligands. The products have been studied by single-crystal X-ray diffraction and spectroscopic methods, including IR and multinuclear NMR spectroscopy as well as mass spectrometry. The use of partially fluorinated starting materials and ligands allows the modulation of the solubilities of the starting materials and the products as well as the monitoring of the reactions by means of ¹⁹F NMR. The attachment of the CF₃ or F substituent on the isocyanides gives control over the steric bulk and the electronic properties of the ligands and, thus, their reactivity.