Homoleptic Rare‐Earth Carbazolates and the Trends of Their E Redox Potentials: Mixed‐Valent Samarium in 1∞[Sm2(Cbz)5](CbzH) (CbzH = carbazole) and Trivalent Thulium, Neodymium and Gadolinium in [Ln2(Cbz)6

Abstract

AbstractThe solvent‐free melt reaction of carbazole (CbzH, C12H8NH) with samarium metal yields 1∞[Sm2(Cbz)5](CbzH) (1), whilst the melt reactions with thulium, neodymium and gadolinium give [Tm2(Cbz)6] (2), [Nd2(Cbz)6] (3) and [Gd2(Cbz)6] (4), respectively. Compounds 1 and 2 were obtained as single crystals and their crystal structures determined by single‐crystal X‐ray analysis, whilst 3 and 4 were obtained as powders. X‐ray powder diffraction studies show that the gadolinium‐containing complex 4 is isotypic to the thulium complex 2, whereas the neodymium‐containing complex 3 is not. Compound 1 contains alternating SmII and SmIII cations in a chain structure. Complex 2 only exhibits dimeric units of TmIII. Besides Ln−N coordination, the crystal structures of both compounds show η6‐π interactions with the phenyl rings of the carbazolate ligands. This leads to small coordination polyhedra, such as connected tetrahedra of two nitrogen atoms and two η6‐π‐coordinated phenyl rings around SmII, and trigonal bipyramids of five nitrogen atoms around SmIII for 1, as well as tetrahedra of three nitrogen atoms and one η6‐π‐phenyl interaction around TmIII for 2. From the trend of the E redox potentials, the complexes of neodymium and gadolinium are also trivalent. For 1−4 the results of FIR, MIR and Raman spectroscopy as well as simultaneous DTA/TG analyses are also presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)