Lanthanide complexes of a cross-bridged cyclam ligand: Isolation and structural characterization of unusual trinuclear μ3-imido Yb(III) cluster cations and a mixed valence Yb(II/III) salt containing an Yb(II) anion

The reaction of the cross-bridged cyclam ligand H2CBC with divalent ytterbium precursors, Yb[N(SiMe3)2]2[L]2 (L = THF or Et2O) or Yb(C5Me5)2(OEt2) afforded polymeric [Yb(CBC)]n (1), as the primary product. In addition, the Yb[N(SiMe3)2]2[L]2 reactions also afforded a small amount of an unusual mixed valence salt containing a trinuclear Yb(III) cluster cation featuring a triply bridging NH group and a mononuclear Yb(II) anion, {[Yb(CBC)]3[μ3-NH]}+ {Yb[N(SiMe3)2]3}− (2). A related cluster containing an iodide counterion, {[Yb(CBC)]3[μ3-NH]}+ I− (3), was also isolated in one case. The structures of salts 2 and 3 were determined by X-ray crystallography. Reaction of [Yb(CBC)]n with p-tolyldisulfide, (C6H4MeS)2, produced burgundy crystals of [Yb(CBC)(S-p-C6H4Me)]n (4). The 1H NMR spectra of 2 suggests that the trinuclear cation remains intact in THF-d8 solution.