Synthesis, Structure, and Molecular Orbital Studies of Yttrium, Erbium, and Lutetium Complexes Bearing eta(2)-Pyrazolato Ligands: Development of a New Class of Precursors for Doping Semiconductors.
Treatment of yttrium metal with bis(pentafluorophenyl)mercury (1.5 equiv), 3,5-di-tert-butylpyrazole (3 equiv), and pyridine (2 equiv) in toluene at ambient temperature for 120 h afforded tris(3,5-di-tert-butylpyrazolato)bis(pyridine)yttrium(III) (33%). In an analogous procedure, the reaction of erbium metal with 3,5-dialkylpyrazole (alkyl = methyl or tert-butyl), bis(pentafluorophenyl)mercury, and a neutral nitrogen donor (4-tert-butylpyridine, pyridine, n-butylimidazole, or 3,5-di-tert-butylpyrazole) yielded tris(3,5-di-tert-butylpyrazolato)bis(4-tert-butylpyridine)erbium(III) (63%), tris(3,5-di-tert-butylpyrazolato)bis(pyridine)erbium(III) (88%), tris(3,5-di-tert-butylpyrazolato)bis(n-butylimidazole)erbium(III) (48%), tris(3,5-dimethylpyrazolato)bis(4-tert-butylpyridine)erbium(III) (50%), and tris(3,5-di-tert-butylpyrazolato)(3,5-di-tert-butylpyrazole)erbium(III) (59%), respectively. Treatment of tris(cyclopentadienyl)lutetium(III) or tris(cyclopentadienyl)erbium(III) with 3,5-di-tert-butylpyrazole (3 equiv) and 4-tert-butylpyridine (2 equiv) in toluene at ambient temperature for 24 h afforded tris(3,5-di-tert-butylpyrazolato)bis(4-tert-butylpyridine)lutetium(III) (83%) and tris(3,5-di-tert-butylpyrazolato)bis(4-tert-butylpyridine)erbium(III) (41%), respectively. The X-ray crystal structures of all new complexes were determined. The X-ray structure analyses revealed seven- and eight-coordinate lanthanide complexes with all-nitrogen coordination spheres and eta(2)-pyrazolato ligands. Molecular orbital calculations were carried out on dichloro(pyrazolato)diammineyttrium(III). The calculations demonstrate that eta(2)-bonding of the pyrazolato ligand is favored over the eta(1)-bonding mode and give insight into the bonding between yttrium and the pyrazolato ligands. Complexes bearing 3,5-di-tert-butylpyrazolato ligands can be obtained in a high state of purity and sublime without decomposition (150 degrees C, 0.1 mmHg). Application of these complexes as source compounds for chemical vapor deposition processes is discussed.
Pfeiffer
Dirk
D
Department of Chemistry, Wayne State University, Detroit, Michigan 48202, Department of Chemistry, University of Delaware, Newark, Delaware 19716, and Department of Chemical Engineering, University of Wisconsin, Madison, Wisconsin 53706.
Ximba
Bhekumusa J.
BJ
Liable-Sands
Louise M.
LM
Rheingold
Arnold L.
AL
Heeg
Mary Jane
MJ
Coleman
David M.
DM
Schlegel
H. Bernhard
HB
Kuech
Thomas F.
TF
Winter
Charles H.
CH