Jump to main content
Jump to site search

Issue 9, 2014
Previous Article Next Article

Unsymmetrical N-heterocyclic carbenes with a 1,1′-ferrocenediyl backbone

Author affiliations

Abstract

This paper focuses on ferrocene-based expanded-ring N-heterocyclic carbenes (NHCs) of the type [Fe(C5H4–NR–C–NR′–C5H4)] (1-R/R′), which contain two different N-substituents. Three combinations were addressed, with R = neopentyl (Np) in each case and R′ being either 2-adamantyl (Ad), phenyl (Ph) or 9-anthracenylmethyl (Acm). The NHCs were generated by reaction of the corresponding formamidinium tetrafluoroborates [H–1-R/R′][BF4] with lithium diisopropylamide (LDA). While only 1-Np/Ad was sufficiently stable for isolation, 1-Np/Ph and 1-Np/Acm could be efficiently trapped in situ by complexation reactions. Two series of RhI complexes were prepared, viz. [RhCl(cod)(1-R/R′)] (cod = 1,5-cyclooctadiene) by reacting [{Rh(μ-Cl)(cod)}2] with 1-R/R′ and cis-[RhCl(CO)2(1-R/R′)] by reacting [RhCl(cod)(1-R/R′)] with CO. All complexes exhibit pronounced anagostic α-CH⋯Rh interactions, both in solution and in the solid state, in accord with a strong influence of the N-substituents on the steric ligand properties, as is chemically illustrated by the huge reactivity difference of [RhCl(cod)(1-Ad)] (R = R′ = Ad) and [RhCl(cod)(1-Np/Ad)] towards CO, the former complex being inert. Tolman electronic parameter (TEP) values are 2050 ± 1 cm−1 for the unsymmetrical NHCs studied, indicating only a weak influence of the N-substituents on the electronic ligand properties.

Graphical abstract: Unsymmetrical N-heterocyclic carbenes with a 1,1′-ferrocenediyl backbone

Back to tab navigation
Please wait while Download options loads

Supplementary files

Publication details

The article was received on 25 Sep 2013, accepted on 13 Dec 2013 and first published on 16 Dec 2013


Article type: Paper
DOI: 10.1039/C3DT52669K
Citation: Dalton Trans., 2014,43, 3508-3520
  •   Request permissions

    Unsymmetrical N-heterocyclic carbenes with a 1,1′-ferrocenediyl backbone

    S. Rittinghaus, C. Färber, C. Bruhn and U. Siemeling, Dalton Trans., 2014, 43, 3508
    DOI: 10.1039/C3DT52669K

Search articles by author