title: Remote effects of axial ligand substitution in heterometallic Cr≡Cr···M chains.
abstract: The heterometallic complexes CrCrM(dpa)(4)Cl(2) (dpa = 2,2'-dipyridylamide) featuring linear Cl-Cr≡Cr···M-Cl chains can regiospecifically be modified via axial ligand substitution to yield OTf-Cr≡Cr···M-Cl chains (OTf = triflate) with M being Fe, Mn, or Co. The effect of OTf substitution on the Cr side of the molecule has an unusual and profound structural impact on the square-pyramidal transition metal M. Specifically, elongation of the four equatorial M-N(py) bonds and the axial M-Cl bonds by 0.03 and 0.09 Å for Fe and 0.07 and 0.11 Å for Mn is observed. The longer M-Cl and M-N(py) bonds result from subtle interactions between the equatorial dpa ligand and the three metal ions. The equatorial dpa ligand responds to the introduction of the more labile OTf ligand at Cr by binding more strongly to this Cr ion which in turn weakens bonding to M. The ligand field experienced by M can be tuned by changing the Cr axial ligand, and this effect is observed in electrochemical measurements of the iron compounds.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Nippe
authors.forename: Yevgeniya
authors.initials: Y
authors.lastname: Turov
authors.forename: John F
authors.initials: JF
authors.lastname: Berry
mesh_terms: D000577:Amides / Q000737:chemistry*; D002625:Chemistry, Organic / Q000379:methods*; D002857:Chromium / Q000737:chemistry*; D056831:Coordination Complexes / Q000032:analysis / Q000138:chemical synthesis*; D018360:Crystallography, X-Ray; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000032:analysis / Q000138:chemical synthesis*; D011725:Pyridines / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000577:Amides; D056831:Coordination Complexes; D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D002857:Chromium