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)

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]­AlH2 or the gallium amide [HC­{C­(Me)­N­(2,6-iPr2C6H3)}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.