Servicenavigation

Project Details

Back

Projekt Print View

Dimetallocenes

Subject Area Inorganic Molecular Chemistry - Synthesis and Characterisation
Term from 2016 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 317535824
 
Final Report Year 2024

Final Report Abstract

Due to their paramagnetic properties, dimetallocenes of the pentaisopropylcyclopentadienyl metal dinuclear complexes [5CpFe]2 and [5CpNi]2 or the tri(tert-butyl)cyclopentadienyl ligand [Cp'''Ni]2 can easily be combined with the also paramagnetic dihydrides [5CpFe(µ-H)]2 and [5CpNi(µ-H)]2 or [Cp'''Ni(µ-H)]2 can be confused: The bridging hydrido ligands are not detected in the 1H NMR spectrum and are within the error limits of elemental analysis, give signals of weak intensity in the IR spectrum in a spectral range in which other bands dominate and can hardly or not be localized at all in crystal structure analysis. Diferrocene has not yet been conclusively clarified, the dinuclear complex described as dinickelocene is probably a second crystal modification of the dihydrido complex and dichromocene reduction experiments in pentane solution clearly revealed the novel dihydrides [5CpCr(µ-H)]2 and [Cp'''Cr(µ-H)]2 result, because the hydride bridges could be localized in the crystal structure determination of the Cp’’’ derivative. Attempted reduction with the early transition metals titanium, zirconium and hafnium only led to the oxidation state +III; the desired oxidation states +II or +I could not be obtained from the half-sandwich compounds [Cp'''MX3] (X = Cl, Br, OtBu). In a reduction experiment, the starting compound [Cp'''Zr(OCtBu)3] was recovered unchanged after 12 hours of stirring with liquid potassium in boiling toluene. During the reduction of the iron dinuclear complex [5CpFe(µ-Br)]2 in a nitrogen atmosphere, it was found that in the preliminary work there was contamination of the nitrogen complex [5CpFe(µ-N)]2 with bridging hydroxide ligands instead of N- atoms had not noticed. This problem was solved with freshly prepared sodium amalgam, whereupon a sample of [5CpFe(µ-N)]2 gave a correct N value in elemental analysis for the first time. With the pentaalkylcyclopentadienyl ligands with noticeably greater steric complexity than with the pentaisopropylcyclopentadienyl derivative, the addition of LiNMe2 to the 6-dimethylaminopentafulvene iPr4C5=CHNMe2 to form lithium tetraisopropyl-bis(dimethylamino)methylcyclopentadienide was successful, but the addition of isopropyllithium to the 1,2,3,4,6-pentaisopropyl-pentafulvene iPr4C5=CH(CHMe2) to lithium tetraisopropyl(diisopropylmethyl)cyclopentadienide was not successful despite the comparable steric situation. Since the bis(dimethylamino)methyl group is expected to have similar problems in the planned subsequent reactions as the tetraisopropyl-(1-naphthyl)dimethylaminomethyl ligand, which tends to split off the dimethylamino group, the only hope that remains is the tetraisopropyl-diphenylmethyl ligand. Addition of phenyllithium to the 1,2,3,4-tetraisopropyl(6-phenyl)pentafulvene iPr4C5=CHPh afforded the lithium salt of this tetraisopropyl-benzhydrylcyclopentadienide.

Publications

 
 

Additional Information

© 2025 DFG Disclaimer / Copyright / Privacy Policy

Textvergrößerung und Kontrastanpassung