Grafting of [Mn(CH2tBu)2(tmeda)] on silica and comparison with its reaction with a silsesquioxane.
The reaction of [Mn(CH2tBu)2(tmeda)] (1) and a silica partially dehydroxylated at 700 degrees C (SiO(2/700)) yields a single surface species [([triple bond]SiO)Mn(CH2tBu)(tmeda)] (2a; tmeda = tetramethylethylendiamine), while a mixture of 2a and [([triple bond]SiO)2Mn(tmeda)] (2b) is obtained by using SiO(2/200), SiO(2/300), or SiO(2/500) as evidenced by mass balance analysis, and IR and EPR spectroscopy. The reaction of 1 and (c-C5H9)7Si7O12SiOH (3), a soluble silanol that is a molecular model for a silica support, generates the bis-siloxy complex 4, [[(c-C5H9)7Si7O12SiO]2Mn(tmeda)2], in a quantitative yield; compound 4 was characterized by single-crystal X-ray diffraction. These reactions exemplify the limitation of considering molecular silanol derivatives as straightforward and reliable homogeneous models for silica, and address the need for thorough characterization of surface species by the use of surface-science techniques. These studies show the possibility of preparing coordinatively and geometrically unique surface species that would be difficult to prepare by solution chemistry methods; insights into the chemical and physical properties of these surface species are also gained.
Riollet
Virginie
V
Laboratoire de Chimie Organométallique de Surface, UMR 9986 CNRS-CPE Lyon, CPE Lyon, 43 Bd du 11 Novembre 1918, 69616 Villeurbanne Cedex, France.
Quadrelli
Elsje Alessandra
EA
Copéret
Christophe
C
Basset
Jean-Marie
JM
Andersen
Richard A
RA
Köhler
Klaus
K
Böttcher
Rolf-Michael
RM
Herdtweck
Eberhardt
E