From Neutral Zn₄O₄ Clusters to a Cationic ZnO Dimer in Solution

Abstract

The suitability of the tetrameric ZnO aggregates [( i PrO)ZnMe] 4 ( 1a ) and [(Me 3 SiO)ZnMe] 4 ( 1b ) as potential sources for molecular models of low-coordinated zinc centers and active sites on zinc oxide catalysts is reported. The formation and fate of the resulting cationic Zn 4 O 4 degradation products by reaction of 1a and 1b with B(C 6 F 5 ) 3 in the presence of different organic donor substrates have been studied by means of ESI mass spectrometry. While 1a affords the cationic monozinc complexes [MeZn(L)] + ( 2a: L = THF, 2b: 15-c-5, 2c: DMAP), the cluster 1b furnishes in the presence of DMAP [MeZn(OSiMe 3 ) 2 Zn(DMAP) 2 ] + ( 3 ), the first dimeric ZnO aggregate cation in solution, and the [MeB(C 6 F 5 ) 3 ] anion. Additionally, the neutral dinuclear ZnO aggregate [(Me 3 SiO)Zn(C 6 F 5 )thf] 2 ( 4 ) results from Me/C 6 F 5 exchange reactions as the final product, which has been characterized by NMR spectroscopy and a single-crystal X-ray diffraction analysis.