ON STRUCTURES OF 4X5X'4YY'80H₂O AND 4XX'2YY'46H₂O CLATHRATE HYDRATES. E.A. Il'inchik, T.M. Polyanskaya, Institute of Inorganic Chemistry Sib. Branch RAS, Novosibirsk, Russia

In this work, we propose two possible structures with 3-dimensional polyhedral host hydrate frames possessing cage-like voids which are occupied by guest molecules 4X5X'4YY'80H₂O (I) and 4XX'2YY'46H₂O (II). Both frames are built of 4 cage types. In I, these are Pd [5₁₂6₃], Td [5₁₂6₂], Dd [5₁₂], and D [4₂5⁸]. Frame II involves Dd' [4₂5₈6₂] along with Pd, Td, D cages. X and X' guests occupy Pd and Td cages in both structures. Y and Y' occupy Dd and D in I and Dd' and D cages in II. When filling only large Pd and Td cages by the guests of one sort, I and II are simplified to X8,89H₂O and X9,2H₂O, respectively.

Both structures are four-storey when viewed along the c axis. In I, the storeys on the levels Z=0 and 1/2 are built of the immediately connected Pd, Td, and Dd cages in the 8Pd:8Td:4Dd ratio; in II, they are built of the Pd and Dd' cages in the 8Pd:4Dd' ratio. A three-dimensional frame is obtained from a successive superposition of the same storey which is rotated through 90 relative to the preceding one. Thus, 6-, 5-, 4- and 6-, 4-angle windows are located over each other and as a result, infinite columns of the Td, Dd, D and Td, D cages with their centers on the Z=1/4 and 3/4 levels are formed in I and II, respectively. In the intermediate storeys, the cages on these levels are not connected immediately. They have the 2Td:4Dd:2D ratio in I and 2Td:2D in II.

In both structures, there are combined voids (4Td and 2Td2Pd in I and 2Td2Pd in II) suitable for the arrangement of the cations of quaternary alkyl salts. Crystal data for I: tetragonal I4(-)c2,a=31,1, c=12.0 , Z=4, 59 positional parameters of 21 symmetrically inequivalent oxygens of H₂O molecules; for II: I4/mcm, a=23,3, c=12.0 , Z=4, 19 positional parameters of 9 oxygens. The unit cell parameters are given in this work for corresponding clathrasiles, silicides, germanides and stannides isotypic with the gas hydrate frame.