Web Release Date: October 12,
Organometallic Synthesis of Colloidal 
-/
-NiAl Nanoparticles and
Selective Aluminum Oxidation in -Ni1-xAlx Nanoalloys
and
Lehrstuhl für Anorganische Chemie II-Organometallics and Materials, Lehrstuhl für Physikalische Chemie I, and Lehrstuhl für Technische Chemie, Ruhr-Universität Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany
Received May 24, 2007
Revised Manuscript Received September 4, 2007
Abstract:
A novel soft chemical synthesis of Ni1-xAlx nanoparticles (0.09 
x 0.50) by cohydrogenolysis of
[Ni(cod)2] (1) with [(AlCp*)4] (2) or with [(Me3N)AlH3] (3) in nonaqueous solution is presented (cod =
1,5-cyclooctadiene, Cp* = 1,2,3,4,5-cyclopentadienyl). The treatment of equimolar amounts of 1 and 2
in mesitylene solution under 3 bar of H2 at 150 
C gave a brown-black colloidal solution of intermetallic
-NiAl particles, characterized by transmission electron microscopy/energy dispersive X-ray analysis
(TEM/EDX) and powder X-ray diffraction (XRD). The solution was stable under 3 bar of H2 at 150 C
for up to 8 h. The -NiAl colloids were treated postsynthesis with 17O-enriched 1-adamantanecarboxylic
acid (ACA) as a surface capping group, giving nearly monodisperse -NiAl colloids that were stable
under argon at room temperature for weeks. The coordination of ACA at the -NiAl surface was studied
by 17O NMR and IR spectroscopy. A series of -Ni1-xAlx samples with a variety of compositions (x =
0.50, 0.33, 0.25, 0.17, 0.09) were prepared analogously, and the samples were characterized by means of
elemental analysis (ICP), XRD, and TEM/EDX. Air oxidation of -Ni1-xAlx nanoparticles leads to core-shell particles of the type (Al2O3)
/2@Ni1-xAlx- (0.09 x 0.50; x > ). XRD, X-ray photoelectron
spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) analyses showed that the Ni core is
protected against oxidation down to an Al content of about 10 atom %.
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