[NPHME(3)](6)[SI8O18(OH)(2)]CENTER-DOT-38.7H(2)O AND [NBNME(3)](8)[SI8O20]CENTER-DOT-53.6H(2)O, HETERONETWORK CLATHRATES WITH 3-DIMENSIONAL MIXED SILICATE-WATER HOST STRUCTURES AND CHANNEL SYSTEMS

The phenyltrimethylammonium and benzyltrimethylammonium silicate hydrates with the approximate chemical compositions [NPhMe(3)](6)[Si8O18(OH)(2)]. 38.7H(2)O (1) and [NBnMe(3)](8)[Si8O20]. 53.6H(2)O (Ph=phenyl, Me=methyl, Bn=benzyl) (2) have been prepared, and their crystal structures were determined by single-crystal X-ray diffraction methods. Crystal data: 1: monoclinic, P2(1)/n, Z=4, a=23.70(1) Angstrom, b=15.733(5) Angstrom, c=28.49(1) Angstrom, beta=93.72(4)degrees, T=225 K; 2: triclinic, P $($) over bar$$ 1, Z=2, a=15.48(1) Angstrom, b=18.594(6) Angstrom, c=25.413(5) Angstrom, alpha=78.42(3)degrees, beta=87.03(4)degrees, gamma=86.74(7)degrees, T=175 K. Compounds 1 and 2 are host-guest compounds with mixed three-dimensional host structures composed of cube-shaped octameric silicate anions and water molecules linked via hydrogen bonds O-H ... O (heteronetwork clathrates). The microchannels in 1 and 2, which open up into rather large cavities in 2, are occupied by the quaternary ammonium cations, [NPhMe(3)](+) or [NBnMe(3)](+), as guest species. The cube-shaped oligomeric [Si8O18(OH)(2)](6-) and [Si8O20](8-) anions are stabilized within very similar local organic-water surroundings by O-H ... O bonds as well as electrostatic and Van der Waals O ... CH3(N) and O ... CH2(N) anion-cation interactions. Some features of the crystal structures are of considerable interest with regard to a recently proposed mechanism for the formation of mesostructured silicate-surfactant composite materials (M41S) in alkaline solution.