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Nanocrystalline Lanthanide Nitride Materials Synthesised by Thermal Treatment of Amido and Ammine Metallocenes: X‐ray Studies and DFT Calculations
Author(s) -
Baisch Ulrich,
Pagano Sandro,
Zeuner Martin,
Barros Noémi,
Maron Laurent,
Schnick Wolfgang
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200501329
Subject(s) - lanthanide , cyclopentadienyl complex , nanocrystalline material , raman spectroscopy , chemistry , thermal decomposition , crystallography , nitride , inorganic chemistry , analytical chemistry (journal) , organic chemistry , catalysis , ion , physics , optics , layer (electronics)
The decomposition process of ammine lanthanide metallocenes was studied by X‐ray diffractometry, spectroscopy and theoretical investigations. A series of ammine‐tris(η 5 ‐cyclopentadienyl)lanthanide( III ) complexes 1 ‐Ln (Lanthanide (Ln)=Sm, Gd, Dy, Ho, Er, Yb) was synthesised by the reaction of [Cp 3 Ln] complexes (Cp=cyclopentadienyl) with liquid ammonia at −78 °C and structurally characterised by X‐ray diffraction methods, mass spectrometry and vibrational (IR, Raman) spectroscopy. Furthermore, amido‐bis(η 5 ‐cyclopentadienyl)lanthanide( III ) complexes 2 ‐Ln (Ln=Dy, Ho, Er, Yb) were synthesised by heating the respective ammine adduct 1 ‐Ln in an inert gas atmosphere at temperatures of between 240 and 290 °C. X‐ray diffraction studies, mass spectrometry and vibrational (IR, Raman) spectroscopy were carried out for several 2 ‐Ln species and proved the formation of dimeric μ 2 ‐bridged compounds. Species 1 ‐Ln are highly reactive coordination compounds and showed different behaviour regarding the decomposition to 2 ‐Ln. The reaction of 1 ‐Ln and 2 ‐Ln with inorganic bases yielded lanthanide nitride LnN powders with an estimated crystallite size of between 40 and 90 nm at unprecedented low temperatures of 240 to 300 °C. Temperature‐dependent X‐ray powder diffraction and transmission electron microscopy (TEM) investigations were performed and showed that the decomposition reaction yielded nanocrystalline material. Structural optimisations were carried out for 1 ‐Ln and 2 ‐Ln by employing density functional (DFT) calculations. A good agreement was found between the observed and calculated structural parameters. Also, Gibbs free energies were calculated for 1 ‐Ln, 2 ‐Ln and the pyrolysis reaction to the nitride material, and were found to fit well with the expected ranges.