Chemistry Reference
In-Depth Information
Fig. 7 Stereopair showing the tetrahedral framework of the NON-type clathrasils
nonahedron [4
1
5
8
] and octahedron [5
4
6
4
] cages, producing larger [5
8
6
12
] 20-hedron
one occludes different types of organic molecules used as templates during the
clathrate synthesis.
[5
4
6
4
]
[4
1
5
8
]
[5
8
6
12
].
Cages per unit cell: 8
þ
8
þ
4
þ
þ
Rings per unit cell: (4
4R)
(64
5R)
(48
6R).
Examples of this type of clathrate are:
(a) Oxides:
|(C
5
H
13
N)
4
|[Si
88
[4]
O
176
[2]
]
[
54
]
|(Co(C
5
H
5
)
2
)
4
F
4
|[Si
88
[4]
O
176
[2]
]
[
55
]
Neither clathrate hydrates nor Zintl phases are known for this structure type.
3.2.4 SGT-Type Clathrates
With formula |M
8
M
0
4
|[(T
16
T
0
16
T
00
16
T
000
16
)
P
64
[4]
O
128
[2]
], this clathrate has a skele-
ton formed by two different types of cavities, [4
3
5
6
] nonahedra and larger polyhedra
[5
12
6
8
] of 20 faces, consisting of five- and six-membered rings in a 3:2 ratio. It is
interesting to note that each small [4
3
5
6
] cavity shares its three four-ring faces with
three neighbouring nonahedron cavities, adopting a structure similar to that of the
Cages per unit cell: 8
[4
3
5
6
]
[5
12
6
8
].
þ
4
Rings per unit cell: (12
4R)
þ
(48
5R)
þ
(16
6R).
An example of this type of clathrate is:
(a) Oxides:
|(C
10
H
17
N)
4
|[Si
64
[4]
O
128
[2]
]
Sigma-2
[
56
]
Neither clathrate-hydrates nor Zintl phases of this type are known.
