title: Systematic variation of metal-metal bond order in metal-chromium complexes.
abstract: In the field of metal-metal bonding, the occurrence of stable, multiple bonds between different transition metals is uncommon, and is largely unknown for different first-row metals. Adding to a recently reported iron-chromium complex, three additional M-Cr complexes have been isolated, where the iron site is systematically replaced with other first-row transition metals (Mn, Co, or Ni), while the chromium site is kept invariant. These complexes have been characterized by X-ray crystallography. The Mn-Cr complex has an ultrashort metal-metal bond distance of 1.82 Å, which is consistent with a quintuple bond. The M-Cr bond distances increases across the period from M = Mn to M = Ni, as the formal bond order decreases from 5 to 1. Theoretical calculations reveal that the M-Cr bonds become increasingly polarized across the period. We propose that these trends arise from increasing differences in the energies and/or contraction of the metals' d-orbitals (M vs Cr). The cyclic voltammograms of these heterobimetallic complexes show multiple one-electron transfer processes, from two to four redox events depending on the M-Cr pair.
authors.affiliation: Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Clouston
authors.forename: Randall B
authors.initials: RB
authors.lastname: Siedschlag
authors.forename: P Alex
authors.initials: PA
authors.lastname: Rudd
authors.forename: Nora
authors.initials: N
authors.lastname: Planas
authors.forename: Shuxian
authors.initials: S
authors.lastname: Hu
authors.forename: Adam D
authors.initials: AD
authors.lastname: Miller
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi
authors.forename: Connie C
authors.initials: CC
authors.lastname: Lu