title: Synthesis of open-shell, bimetallic Mn/Fe trinuclear clusters.
abstract: Concomitant deprotonation and metalation of hexadentate ligand platform (tbs)LH6 ((tbs)LH6 = 1,3,5-C6H9(NHC6H4-o-NHSiMe2(t)Bu)3) with divalent transition metal starting materials Fe2(Mes)4 (Mes = mesityl) or Mn3(Mes)6 in the presence of tetrahydrofuran (THF) resulted in isolation of homotrinuclear complexes ((tbs)L)Fe3(THF) and ((tbs)L)Mn3(THF), respectively. In the absence of coordinating solvent (THF), the deprotonation and metalation exclusively afforded dinuclear complexes of the type ((tbs)LH2)M2 (M = Fe or Mn). The resulting dinuclear species were utilized as synthons to prepare bimetallic trinuclear clusters. Treatment of ((tbs)LH2)Fe2 complex with divalent Mn source (Mn2(N(SiMe3)2)4) afforded the bimetallic complex ((tbs)L)Fe2Mn(THF), which established the ability of hexamine ligand (tbs)LH6 to support mixed metal clusters. The substitutional homogeneity of ((tbs)L)Fe2Mn(THF) was determined by (1)H NMR, (57)Fe Mössbauer, and X-ray fluorescence. Anomalous scattering measurements were critical for the unambiguous assignment of the trinuclear core composition. Heating a solution of ((tbs)LH2)Mn2 with a stoichiometric amount of Fe2(Mes)4 (0.5 mol equiv) affords a mixture of both ((tbs)L)Mn2Fe(THF) and ((tbs)L)Fe2Mn(THF) as a result of the thermodynamic preference for heavier metal substitution within the hexa-anilido ligand framework. These results demonstrate for the first time the assembly of mixed metal cluster synthesis in an unbiased ligand platform.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors.forename: Tamara M
authors.initials: TM
authors.lastname: Powers
authors.forename: Nina X
authors.initials: NX
authors.lastname: Gu
authors.forename: Alison R
authors.initials: AR
authors.lastname: Fout
authors.forename: Anne M
authors.initials: AM
authors.lastname: Baldwin
authors.forename: Raúl
authors.initials: R
authors.lastname: Hernández Sánchez
authors.forename: Denise M
authors.initials: DM
authors.lastname: Alfonso
authors.forename: Yu-Sheng
authors.initials: YS
authors.lastname: Chen
authors.forename: Shao-Liang
authors.initials: SL
authors.lastname: Zheng
authors.forename: Theodore A
authors.initials: TA
authors.lastname: Betley
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis*; D005296:Ferrous Compounds / Q000737:chemistry*; D008024:Ligands; D008345:Manganese / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D005296:Ferrous Compounds; D008024:Ligands; D008345:Manganese