title: Structure and bonding of group 4-nickel heterobimetallics supported by 2-(diphenylphosphino)pyrrolide ligands.
abstract: The synthesis of a full series of group 4/nickel complexes supported by a 2-(diphenylphosphino)pyrrolide (NP) ligand is reported. Treatment of the homoleptic, 8-coordinate M(NP)4 monometallic precursors with Ni(COD)2 (COD = 1,5-cyclooctadiene) yielded the heterobimetallic complexes (κ(2)-NP)M(μ2-NP)3Ni (M = Ti, Zr, Hf). Although X-ray crystallographic analysis reveals similarly short metal-metal distances in all three complexes, quantum chemical calculations indicate that ZrNi () and HfNi () contain only single Ni → M dative bonds while TiNi () has an additional Ti-Ni π-bond. All three complexes have quasireversible reductions by cyclic voltammetry, and 1-electron chemical reduction of by Na(Hg) yields the anion, [Na][(κ(2)-NP)Ti(μ2-NP)3Ni] (). X-ray and computational analysis indicate that the 1-electron reduction of completely breaks the metal-metal bond, yielding a formally Ti(III)-Ni(0) complex. Ti-Ni bonding can also be disrupted by coordination of CO, wherein Ni → CO backbonding effectively outcompetes Ni → Ti dative bonding.
authors.affiliation: Department of Chemistry, University of Minnesota - Twin Cities, 207 Pleasant St SE, Minneapolis, MN 55455, USA. itonks@umn.edu.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Dunn
authors.affiliation: Department of Chemistry, University of Minnesota - Twin Cities, 207 Pleasant St SE, Minneapolis, MN 55455, USA. itonks@umn.edu and Supercomputing Institute and Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Rebecca K
authors.initials: RK
authors.lastname: Carlson
authors.affiliation: Department of Chemistry, University of Minnesota - Twin Cities, 207 Pleasant St SE, Minneapolis, MN 55455, USA. itonks@umn.edu and Supercomputing Institute and Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi
authors.affiliation: Department of Chemistry, University of Minnesota - Twin Cities, 207 Pleasant St SE, Minneapolis, MN 55455, USA. itonks@umn.edu.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Tonks