The Pentagallium Cation in Zeolite Y. Preparation and Crystal Structure of Ga_(42)Tl_(9.3)-Si_(121)Al_(71)O_(384) Containing Ga5~(7+), Ga~+, Ga~(2+), Ga~(3+), and Tl~+

摘要

The extraframework gallium cations GaGa5~(7+), Ga~+, Ga~(2+), and Ga~(3+) have been introduced into zeolite Y. Ga,Tl-Y (GacTl"-Y or |(Ga5~(7+))_(5.8)Ga_(6.6)~+Ga~(2+)_(4.8)Ga~(3+)_(1.5) Tl~+_(93)| [Si_(121)Al_(71)O_(384)] -FAU) was prepared by the reaction of Tl_(71)- Y with Ga° under anhydrous conditions at 623 K. Its structure was determined by single-crystal crystallography with synchrotron X-radiation, and its composition was confirmed by energy dispersive X-ray analysis. The structure was refined in the space group Fd3m (a = 24.527(1) A; with all 1126 unique data; the final error index, R1 = 0.074, was calculated using only the 935 reflections with F_o > 4σ(F_o). Ga~0 reacted with 87% of the Tl~+ ions in the zeolite, mostly to give Ga_5~(7+) cations (centered tetrahedral, Ga-Ga = 2.512(3) A). Ga_5~(7+) centers 5.8 of the 8 sodalite cavities per unit cell; each terminal atom (at site I') bonds to three framework oxygen atoms of a double 6-ring (Ga- O = 2.050(S) A and O- Ga-O= 99.0(2)°). The remaining Ga ions occupy five crystallographkally distinct cationic sites: 2.3 Ga~+ at site I', 4.3 Ga~+ at site II, 2.1 Ga~(2+) at a second site II, 2.7 Ga~(2+) at site III', and 1.5 Ga~(3+) at a second site I'. The gallium ions at sites I' and II bond only to three 6-ring oxygen atoms; those at sites II and III' extend into the supercage and are easily accessible for sorption and catalysis. All Tl~+ ions occupy supercage sites.