title: Synthesis, structures and reactivity of lanthanoid(II) formamidinates of varying steric bulk.
abstract: New reactive, divalent lanthanoid formamidinates [Yb(Form)(2)(thf)(2)] (Form=[RNCHNR]; R=o-MeC(6)H(4) (o-TolForm; 1), 2,6-Me(2)C(6)H(3) (XylForm; 2), 2,4,6-Me(3)C(6)H(2) (MesForm; 3), 2,6-Et(2)C(6)H(3) (EtForm; 4), o-PhC(6)H(4) (o-PhPhForm; 5), 2,6-iPr(2)C(6)H(3) (DippForm; 6), o-HC(6)F(4) (TFForm; 7)) and [Eu(DippForm)(2)(thf)(2)] (8) have been prepared by redox transmetallation/protolysis reactions between an excess of a lanthanoid metal, Hg(C(6)F(5))(2) and the corresponding formamidine (HForm). X-ray crystal structures of 2-6 and 8 show them to be monomeric with six-coordinate lanthanoid atoms, chelating N,N'-Form ligands and cis-thf donors. However, [Yb(TFForm)(2)(thf)(2)] (7) crystallizes from THF as [Yb(TFForm)(2)(thf)(3)] (7a), in which ytterbium is seven coordinate and the thf ligands are "pseudo-meridional". Representative complexes undergo C-X (X=F, Cl, Br) activation reactions with perfluorodecalin, hexachloroethane or 1,2-dichloroethane, and 1-bromo-2,3,4,5-tetrafluorobenzene, giving [Yb(EtForm)(2)F](2) (9), [Yb(o-PhPhForm)(2)F](2) (10), [Yb(o-PhPhForm)(2)Cl(thf)(2)] (11), [Yb(DippForm)(2)Cl(thf)] (12) and [Yb(DippForm)(2)Br(thf)] (16). X-ray crystallography has shown 9 to be a six-coordinate, fluoride-bridged dimer, 12 and 16 to be six-coordinate monomers with the halide and thf ligands cis to each other, and 11 to have a seven-coordinate Yb atom with "pseudo-meridional" unidentate ligands and thf donors cis to each other. The analogous terbium compound [Tb(DippForm)(2)Cl(thf)(2)] (13), prepared by metathesis, has a similar structure to 11. C-Br activation also accompanies the redox transmetallation/protolysis reactions between La, Nd or Yb metals, Hg(2-BrC(6)F(4))(2), and HDippForm, yielding [Ln(DippForm)(2)Br(thf)] complexes (Ln=La (14), Nd (15), Yb (16)).
authors.affiliation: School of Chemistry, Monash University, Victoria 3800, Australia.
authors.forename: Marcus L
authors.initials: ML
authors.lastname: Cole
authors.forename: Glen B
authors.initials: GB
authors.lastname: Deacon
authors.forename: Craig M
authors.initials: CM
authors.lastname: Forsyth
authors.forename: Peter C
authors.initials: PC
authors.lastname: Junk
authors.forename: Kristina
authors.initials: K
authors.lastname: Konstas
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Henry
authors.initials: H
authors.lastname: Bittig
authors.forename: Daniel
authors.initials: D
authors.lastname: Werner
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D007536:Isomerism; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D015018:Ytterbium / Q000737:chemistry
chemical_list: D056831:Coordination Complexes; D028581:Lanthanoid Series Elements; D015018:Ytterbium