Heterometallic alumo- and gallodisilicates with M(O-Si-O) 2M′ and [M(O-Si-O)2]2M′ Cores (M = Al, Ga; M′ = Ti, Zr, Hf)

Article abstract of DOI:10.1021/ic400156n

The synthesis and stabilization of alumo- and gallodisilicates [HC{C(Me)N(2,6-iPr₂C₆H₃)}₂]M[(μ- O)Si(OH)(OtBu)₂]₂ [M = Al (1), Ga (2)] containing two silicate subunits have been achieved through reactions between 2 equiv of the silanediol (tBuO)₂Si(OH)₂ and the aluminum hydride [HC{C(Me)N(2,6-iPr₂C₆H₃)}₂]AlH ₂ or the gallium amide [HC{C(Me)N(2,6-iPr₂C ₆H₃)}₂]Ga(NHEt)₂, respectively. Compounds 1 and 2 exhibit M(O-SiO₂-OH)₂ moiety and represent the first molecular metallosilicate-based analogues of neighboring silanol groups found in silicate surfaces. The substitution of both SiOH groups led to the formation of bimetallic compounds with 4R topologies, which are regularly found in zeolitic materials. Thus, reactions between group 4 metal amides M′(NEt₂)₄ (M′ = Ti, Zr, Hf) and 1 and 2 resulted in the formation of nine heterometallic silicates (3-11) containing inorganic M(O-Si-O)₂M′ and [M(O-Si-O)₂] ₂M′ cores with 4R and spiro-4R topologies, respectively. The latter have M···M distances of 0.81 nm. NMR studies of the heterometallic derivatives showed a fluxional behavior at room temperature due to a high flexibility of the eight-membered ring.