Synthesis and Characterization of Heterobimetallic Al–O–Cu Complexes toward Models for Heterogeneous Catalysts on Metal Oxide Surfaces

The β-diketiminato aluminum-monohydroxide
and -dihydroxide were reacted with tetrameric (CuMes)4 (Mes
= 2,4,6-Me3C6H2) to prepare Cu­(I)
complexes bearing the Al–O–Cu moiety. All complexes
are characterized by elemental analysis, nuclear magnetic resonance,
and single-crystal X-ray diffraction. The reaction of aluminum–monohydroxide
LAlR­(OH) (L = HC­[C­(Me)­N­(Ar)]2; Ar = 2,6-iPr2C6H3; R = Me, Et) with (CuMes)4 afforded the Cu­(I) alumoxane [LAl­(R)­OCu·MesCu]2 (R = Me, 1; Et, 2). Using the aluminum-dihydroxide
LAl­(OH)2 as the precursor, the dimeric [LAl­(OH)­OCu·MesCu]2 (3) was isolated, bearing one reactive OH group
on each Al center. When the reaction of LAl­(OH)2 with (CuMes)4 was carried out at 70 °C, the dimeric octanuclear Cu­(I)
compound [LAl­(OCu·MesCu)2]2 (4) was formed, where two residual Mes groups are located at the neighboring
position on each of the two (OCu·MesCu)2 squares.
Compound 4 can be alternatively obtained by reacting 3 with 1 equiv of (CuMes)4 to demonstrate the stepwise
assembly of the Cu­(I) alumoxanes.