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Transition Metal Complexes of NHC Ligands Functionalized with the Cationic (η 5 ‐Cyclopentadienyl)(η 6 ‐phenyl)iron(II) Motif
Author(s) -
Malchau Christian,
Fries Daniela V.,
Mees Yannick,
Jakobs Marisa F.,
Sun Yu,
Becker Sabine,
NiednerSchatteburg Gereon,
Thiel Werner R.
Publication year - 2022
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.202200106
Subject(s) - chemistry , transmetalation , carbene , deprotonation , palladium , cyclopentadienyl complex , medicinal chemistry , rhodium , transition metal , ligand (biochemistry) , cationic polymerization , polymer chemistry , catalysis , organic chemistry , ion , biochemistry , receptor
Starting from [(η 5 ‐cyclopentadienyl)(η 6 ‐phenyl)iron(II)]imidazole, dicationic imidazolium salts were prepared by N ‐alkylation. Reaction of these compounds with basic metal precursors such as mesityl copper(I) or palladium(II) acetate led to mono respectively dicationic transition metal NHC complexes (NHC= N ‐heterocyclic carbene). Transmetalation using the copper(I) complexes opened up the access to NHC gold(I) compounds. PEPPSI‐type NHC complexes of palladium(II) and platinum(II) were prepared by offering a neutral pyridine ligand to the transition metal center. A rhodium(I) NHC complex was accessible by deprotonation of the dicationic imidazolium precursor and subsequent treatment with [(COD)Rh(μ 2 ‐Cl)] 2 (COD=1,5‐cyclooctadiene). The new NHC complexes were investigated by means of NMR spectroscopy, mass spectrometry as well as single crystal X‐ray structure analysis. Both, the palladium(II) containing PEPPSI‐type and the gold(I) complex, were investigated for their catalytic properties in typical model reactions such as cyclization reactions, Suzuki coupling and cyanation. In addition, a selenium adduct was synthesized in order to study the electronic properties of the underlying ligand backbone. Based on the chemical shift in the 77 Se NMR spectrum, it is evident that these NHC ligands possess rather poor π‐acidity.