title: Role of the metal in the bonding and properties of bimetallic complexes involving manganese, iron, and cobalt.
abstract: A multidentate ligand platform is introduced that enables the isolation of both homo- and heterobimetallic complexes of divalent first-row transition metal ions such as Mn(II), Fe(II), and Co(II). By means of a two-step metalation strategy, five bimetallic coordination complexes were synthesized with the general formula M1M2Cl(py3tren), where py3tren is the triply deprotonated form of N,N,N-tris(2-(2-pyridylamino)ethyl)amine. The metal-metal pairings include dicobalt (1), cobalt-iron (2), cobalt-manganese (3), diiron (4), and iron-manganese (5). The bimetallic complexes have been investigated by X-ray diffraction and X-ray anomalous scattering studies, cyclic voltammetry, magnetometry, Mössbauer spectroscopy, UV-vis-NIR spectroscopy, NMR spectroscopy, combustion analyses, inductively coupled plasma optical emission spectrometry, and ab initio quantum chemical methods. Only the diiron chloride complex in this series contains a metal-metal single bond (2.29 Å). The others show weak metal-metal interactions (2.49 to 2.53 Å). The diiron complex is also distinct with a septet ground state, while the other bimetallic species have much lower spin states from S = 0 to S = 1. We propose that the diiron system has delocalized metal-metal bonding electrons, which seems to correlate with a short metal-metal bond and a higher spin state. Multiconfigurational wave function calculations revealed that, indeed, the metal-metal bonding orbitals in the diiron complex are much more delocalized than those of the dicobalt analogue.
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Tereniak
authors.forename: Rebecca K
authors.initials: RK
authors.lastname: Carlson
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Clouston
authors.forename: Victor G
authors.initials: VG
authors.lastname: Young
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.forename: Rémi
authors.initials: R
authors.lastname: Maurice
authors.forename: Yu-Sheng
authors.initials: YS
authors.lastname: Chen
authors.forename: Hyun Jung
authors.initials: HJ
authors.lastname: Kim
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi
authors.forename: Connie C
authors.initials: CC
authors.lastname: Lu
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure
chemical_list: D056831:Coordination Complexes; D003035:Cobalt; D008345:Manganese; D007501:Iron