Formation and structural properties of 1,1′,2,2′-tetra(tert-butylcarbamoyl)-ferrocene and -ruthenocene†

Abstract

Sodium cyclopentadienide adds two molar equivalents of tert-butylisocyanate to yield the 1,2-bis(N-tert-butylcarbamoyl)cyclopentadienide reagent 1. This reacts with RuCl₂(PPh₃)₄ 3 in a 2∶1 stoichiometry to yield the metallocene [η⁵-C₅H₃(CONHCMe₃)₂]₂Ru 5. Complex 5 was characterized by an X-ray crystal structure analysis. It shows a near to eclipsed C₂-symmetric metallocene conformation with the carboxamide substituents pairwise connected by intramolecular hydrogen bridges between –CONHR groups attached to different Cp ligands. The intermediate of the substitution reaction sequence, the complex [η⁵-C₅H₃(CONHCMe₃)₂]RuCl(PPh₃)₂ 4, was also isolated and characterized by X-ray diffraction. Treatment of 1 with FeCl₂ (2∶1) yields 1,1′,2,2′-tetra(N-tert-butylcarbamoyl)ferrocene 6. The X-ray crystal structure analysis of 6 features a staggered C_i metallocene conformation.