title: 1,1'-Bis(N-benzimidazolylidene)ferrocene: synthesis and study of a novel ditopic ligand and its transition metal complexes.
abstract: Diiridum complexes containing 1,1'-bis(N-benzimidazolylidene)ferrocene, a novel ditopic ligand comprised of two N-heterocyclic carbenes (NHCs) linked directly via their N-substituents to each cyclopentadienyl ring of a ferrocene moiety, were synthesized. Crystallographic analyses of these C(2)-symmetric bimetallic complexes revealed the benzimidazolylidene moieties were intramolecularly stacked in nearly opposing orientations, effectively forming Janus-type bis(NHC) structures in the solid state. Using a variety of electrochemical techniques, the oxidation potentials of the ferrocenyl groups in these complexes were found to depend on the auxillary ligands coordinated to the Ir centers (i.e., 1,5-cyclooctadiene vs. carbonyl). Similarly, the nu(CO) of carbonyls ligated to the Ir centers varied in accord with the oxidation state of the ferrocene contained with the bis(NHC) ligand. These results suggest that the Ir and Fe centers in these complexes are electronically coupled and that the electron donating ability of the bis(NHC) ligand reported herein can be tuned electrochemically.
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, TX 78712, USA.
authors.forename: C Daniel
authors.initials: CD
authors.lastname: Varnado
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Lynch
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Bielawski
mesh_terms: D001562:Benzimidazoles / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D008024:Ligands; D000075163:Metallocenes; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism
chemical_list: C551235:1,1'-bis(N-benzimidazolylidene)ferrocene; D001562:Benzimidazoles; D005296:Ferrous Compounds; D006571:Heterocyclic Compounds; D008024:Ligands; D000075163:Metallocenes; D009942:Organometallic Compounds; C030011:carbene; D007495:Iridium; D008697:Methane