title: Ferromagnetic Coupling in "Double-Bridged" Dihydrogenpyrophosphate Complexes of Cobalt(II) and Nickel(II).
abstract: Three isostructural compounds of the formula {[M(bipy)(H2O)(H2P2O7)]2·2H2O} [bipy = 2,2'-bipyridine; M = Ni (1), Co (2), Mn (3)] have been isolated from aqueous solutions containing the corresponding metal(II) chloride hydrate with a bipy and sodium pyrophosphate solution in a 1:1:2 molar ratio, and their structures were determined by single-crystal X-ray diffraction. The structures of 1-3 consist of neutral aqua(2,2'-bipyridine)metal(II) dinuclear units bridged by two dihydrogenpyrophosphate groups adopting a bidentate/monodentate mode. Each metal ion in 1-3 is six-coordinate in a distorted octahedral geometry, with the reduced value of the angle subtended by the chelating bipy at the metal ion [79.6(1)° (1), 77.32(7)° (2), and 72.9(1)° (3)] being the main source of this distortion. The values of the intramolecular metal-metal separation are 5.271(1) Å (1), 5.3065(8) Å (2), and 5.371(1) Å (3). Magnetic susceptibility measurements on polycrystalline samples of 1-3 in the temperature range 1.9-300 K shows weak intramolecular ferromagnetic [J = +1.86(2) cm(-1) (1) and +0.25(1) cm(-1) (2)] and antiferromagnetic [J = -0.48(1) cm(-1) (3)] coupling, with the spin Hamiltonian being defined as H = -JSM1·SM1a. This rarely observed coordination mode for dihydrogenpyrophosphate leads to ferromagnetic coupling in complexes of nickel(II) or cobalt(II).
authors.affiliation: †Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100, United States.
authors.forename: Tiffany J
authors.initials: TJ
authors.lastname: Greenfield
authors.affiliation: †Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100, United States.
authors.forename: Amanda E
authors.initials: AE
authors.lastname: Hoffman
authors.affiliation: †Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100, United States.
authors.forename: Nadia
authors.initials: N
authors.lastname: Marino
authors.affiliation: †Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100, United States.
authors.forename: Alan G
authors.initials: AG
authors.lastname: Goos
authors.affiliation: ‡Departament de Quimica Inorganica/Instituto de Ciencia Molecular, Facultat de Química, Universitat de València, Catedratico Jose Beltran 2, 46980 Paterna, Valencia, Spain.
authors.forename: Francesc
authors.initials: F
authors.lastname: Lloret
authors.affiliation: ‡Departament de Quimica Inorganica/Instituto de Ciencia Molecular, Facultat de Química, Universitat de València, Catedratico Jose Beltran 2, 46980 Paterna, Valencia, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Julve
authors.affiliation: †Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100, United States.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Doyle