title: Stabilizing coordinated radicals via metal-ligand covalency: a structural, spectroscopic, and theoretical investigation of group 9 tris(dithiolene) complexes.
abstract: Proper assignment of redox loci in coordination complexes with redox-active ligands to either the metal or the ligand is essential for rationalization of their chemical reactivity. However, the high covalency endemic to complexes of late, third-row transition metals complicates such assignments. Herein, we systematically explore the redox behavior of a series of group 9 tris(dithiolene) complexes, [M(mnt)3]3– (M = Ir, Rh, Co; mnt = maleonitriledithiolate). The Ir species described comprise the first examples of homoleptic Ir dithiolene complexes. The enhanced metal–ligand covalency of the Ir–S interaction leads to remarkable reactivity of [Ir(mnt)3]3– and stabilization of mononuclear [Ir(mnt)3]2– complex ions as well as dimerized versions featuring weak, covalent, intermolecular S–S bonds. The dianionic Rh and Co analogues are, in contrast, highly unstable, resulting in the rapid formation of [Rh2(mnt)5]4– and [Co(mnt)2]22–, respectively. The synthesized complexes were studied by single-crystal X-ray diffraction, X-ray absorption spectroscopy, optical spectroscopy, magnetometry, density functional theory, and spectroscopy-oriented configuration interaction calculations. Spectroscopic and theoretical analyses suggest that the stability of [Ir(mnt)3]2– may be attributed to dilution of ligand radical character by a high degree of Ir 5d character in the singly occupied molecular orbital.
authors.affiliation: †Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States.|‡Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
authors.forename: Thorbjørn J
authors.initials: TJ
authors.lastname: Morsing
authors.affiliation: †Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States.
authors.forename: Samantha N
authors.initials: SN
authors.lastname: MacMillan
authors.affiliation: †Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States.
authors.forename: Jacob W H
authors.initials: JW
authors.lastname: Uebler
authors.affiliation: ‡Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
authors.forename: Theis
authors.initials: T
authors.lastname: Brock-Nannestad
authors.affiliation: ‡Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Bendix
authors.affiliation: †Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States.
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Lancaster