Michael Wiebcke

N(nPr)4[B5O6(OH)4][B(OH)3]2 and N(nBu)4[B5O6(OH)4][B(OH)3]2: Clathrates with a diamondoid arrangement of hydrogen-bonded pentaborate anions

Single-crystal X-ray structure analyses of N(nPr)4[B5O6(OH)4][B(OH)3]2,1, and N(nBu)4 [B5O6(OH)4][B(OH)3]2,2, reveal that these materials are novel clathrates, the isotypic host structures of which are three-dimensional assemblies of hydrogen-bonded [B5O6(OH)4]− ionsand B(OH)3 molecules. The assembly of only the pentaborate anions is a distorted (i.e., along [102] elongated) fourconnected diamond-related network. The N(nPr)4+ and N(nBu)4+ ions are trapped within the complex three-dimensional channel systems of the host frameworks. Both1 and2 crystallize monoclinically with space groupP21/c andZ=4. The cell constants are:1:a=13.592(5),b=12.082(2),c=17.355(6) Å, β=106.60(2)° (298K);2:a=13.874(3),b=12.585(1),c=17.588(4) Å, β=107.04(1)° (238 K). The results obtained by both11B and13C MAS NMR spectroscopy are discussed. Thermogravimetric studies under a flowing inert-gas atmosphere suggest that water, stemming from polycondensation of the hydrous borate species, is released from the clathrates at ca. 443 K (1) and 398 K (2) before the decomposition of the organic cations starts at ca. 603 K (1) and 603 K (2).

Structural links between zeolite-type and clathrate hydrate-type materials: Redetermination of the crystal structure of [N(CH3)4]8[Si8O20]·65H2O by single-crystal X-ray diffraction and variable-temperature MAS NMR spectroscopy

Abstract The tetramethylammonium silicate hydrate [NMe4]8[Si8O20]·65H2O (1 hereafter) crystallizes triclinically with space group P 1 , Z = 1 and the cell constants a = 15.644(3), b = 15.756(4), c = 15.967(5) A, α = 119.31(2), β = 108.83(2), γ = 91.99(2)° (T = 215 K). It is shown that the polyhydrate is a host—guest compound with a mixed three-dimensional host structure composed of oligomeric [Si8O20]8− anions and H2O molecules linked via hydrogen bonds Oue5f8H⋯O (heteronetwork clathrate). The silicate anions possess a cube-shaped double four-ring structure. Four distinct large, irregular, cage-like voids house the guest species NMe4+. MAS NMR spectra measured at various temperatures between 170 and 290 K reveal that the 13C resonance of the NMe4+ cation is shifted continuously to higher field with decreasing temperature and depends primarily on the chemical composition of the cage wall rather than on the cage size. At room temperature the 1H MAS NMR spectrum is well resolved, suggesting that both the H2O molecules and NMe4+ cations are highly mobile on the NMR time scale. The water dynamics slow down at temperatures below ca. 250 K which in turn affects the motions of the guest species. The polyhydrate melts incongruently at 345 K with the formation of a liquid phase and a crystalline heteronetwork clathrate, the host structure of which possesses the topology of the zeolite structure type AST.

The tetraethylammonium cation in a double three-ring silicate heteronetwork clathrate and a polyhedral clathrate hydrate : low-temperature single-crystal X-ray diffraction studies on (NEt4)6[Si6O15].40.8H2O and NEt4OH.9H2O

Abstract A reinvestigation of the crystal structure of the tetraethylammonium silicate hydrate with the approximate chemical composition (C 8 H 20 N) 6 [Si 6 O 15 ]xa0·xa040.8H 2 O ( 1 ) is reported. The crystal structure of tetraethylammonium hydroxide nonahydrate, (C 8 H 20 N)OHxa0·xa09H 2 O ( 2 ), has been determined for the first time. The structure of 1 has been refined to much higher precision in the centrosymmetric space group P 1 (Z=2) with a considerable degree of disorder, compared to a previous structure analysis in the non-centrosymmetric space group P1 without disorder (Sov. Phys. Crystallogr. 29 (1984) 421). 1 may be considered as a host–guest compound, in which trigonal-prismatic double three-ring silicate anions and water molecules form a complicated hydrogen-bonded host structure. The organic guest cations reside in straight channels and very irregular, not completely closed cages. The [Si 6 O 15 ] 6− oligoanions are stabilized in a specific organic–water environment by O–Hxa0⋯xa0O hydrogen bonds and electrostatic and van der Waals O ⋯ CH 3 and O ⋯ CH 2 ( N ) anion–cation interactions. The NEt + 4 cations occur as conformers of approximate 4 2m(D 2d ) and 4 (S 4 ) molecular symmetry, depending on the location around the oligoanion. 2 is the first representative of a polyhedral clathrate hydrate of the NEt + 4 cation. The novel host structure is built from hydrogen-bonded water molecules and hydroxide ions.

Clathrates with Three-Dimensional Host Structures of Hydrogen-Bonded Pentaborate [B5O6(OH)4]- Ions: Pentaborates with the Cations NMe4+, NEt4+, NPhMe3+ and pipH+ (pipH+ = Piperidinium)

X-ray structure analyses of crystalline [NMe4][B5O6(OH)4] · nH2O with n ≈ 0.25-0.50 (1), [NEt4][B5O6(OH)4] (2), [NPhMe3][B5O6(OH)4] (3), and [pipH][B5O6(OH)4] (4) reveal that these materials are novel clathrates with closely related three-dimensional host structures built up of hydrogen-bonded oligomeric pentaborate [B5O6(OH)4]- ions. The organic cations and water molecules (in 1) occupy as guest species large straight channel-like voids of nearly rectangular cross-section. Compound 1 crystallizes monoclinically with space group P2,/c (Z = 4); the compounds 2,3 and 4, which possess the same host-structure topology, crystallize triclinically with space group P1̄ (Z = 2). 11B-MAS NMR spectra allow the detection of small angular distortions in the pentaborate anions caused by the specific hydrogen bonding in the host frameworks. Upon heating the compounds on a thermobalance in a dynamic inert gas atmosphere dehydration occurs at temperatures of 563 K (1), 543 K (2), 558 K (3) and 523 K (4) before degradation of the organic cations starts at temperatures of 633 K (1), 623 K (2), 623 K (3) and 613 K (4).

Structural links between zeolite-type and clathrate hydrate-type materials: strands of small clusters of water molecules interconnect oligomeric silicate [Si8O18(OH)2]6– anions to generate the 3D host structure of the heteronetwork clathrate [DMPI]6[Si8O18(OH)2]·48.5h2O (DMPI = 1,1-dimethylpiperidinium)

The mixed silicate–water host framework, 3∞[{[Si8O18(OH)2]6–}2[H2O]97], of the title compound contains unprecedented and remarkable structural features, e.g. pseudo-hexagonal layer-like subunits with large circular apertures (free diameter ca. 7.9 A) that resemble layer-like structural units of large-pore zeolite-type materials; the preparation and X-ray structure of the heteronetwork clathrate are reported.

Two polymorphs of a piperazinium zincophosphate with different interrupted SOD-type frameworks

Abstract Two polymorphous forms of the piperazinium zincophosphate (ZnPO) (C 4 N 2 H 12 )[Zn 2 P 3 O 12 H 3 ] have been obtained under mild hydrothermal conditions from mixtures of ZnCl 2 , H 3 PO 4 piperazine and H 3 BO 3 in ethylene glycol/water solvents. Single-crystal X-ray structure analyses revealed that both polymorphs possess an open-framework structure with sodalite (SOD) topology. While polymorph I (formulation (C 4 N 2 H 12 )[Zn 2 (HPO 4 ) 3 ], space group P2 1 /c, Z =8) is reported for the first time, polymorph II (formulation (C 4 N 2 H 12 )[Zn 2 (PO 4 )(H 1.5 PO 4 ) 2 ], space group C2/c, Z =4) is a known phase. Its structure has been reinvestigated in order to unambiguously determine the hydrogen bonds. The interruptions in the ZnPO host structures possess the form of distorted tetrahedral [H 3 O 4 (P) 4 ] groupings (hydroxyl nests). A diprotonated piperazine molecule is enclosed in every [4 6 6 8 ] cage. The polymorphs differ in the host–guest N–H⋯O and C–H⋯O interactions, the degree of condensation of the distinct phosphate tetrahedra, the hydrogen-bonding systems in the interruptions, and the long-range ordering of interruptions in the host frameworks. Considerable differences are seen for the donor–acceptor O⋯O distances (ranging from 2.47 to 3. 14 A) in the total of three distinct [H 3 O 4 (P) 4 ] groupings.

NEt4OH·4H2O containing infinite hydro­xide–water ribbons

In tetraethylxadammonium hydroxadxide tetrahydrate, C8H20N+·xadOH−·xad4H2O, the array of mirror symmetric NEt4+ cations gives rise to a system of parallel channels which are filled with hydrogen-bonded anionic ribbons. The central part of each ribbon is constituted by a [OH−(HOH)4/2] spiro-chain, with each hydroxadxide ion accepting four strong linear hydrogen bonds [d(O⋯O) between 2.692u2005(1) and 2.727u2005(1)u2005A] but donating none. Additional (two-coordinate) H2O molxadecules bridge between the (four-coordinate) H2O molxadecules of the spiro-chain [d(O⋯O) between 2.831u2005(1) and 2.835u2005(1)u2005A].

Brønsted conjugate acid–base species b(OH)3)/[BO(OH)2]– coexist in the crystalline solid (NEt4)2[BO(OH)2]2·B(OH)3·5H2O

X-ray structure analysis reveals that in the title compound, which crystallizes in the ternary system (NEt4)2O–B2O3–H2O from strongly basic solutions, extensive intermolecular hydrogen bonding links the species B(OH)3, [BO(OH)2]– and H2O into two-dimensional anionic layers that are interleaved by NEt4+ cations.

Lead hydro sodalite [Pb2(OH)(H2O)3]2[Al3Si3O12]2: synthesis and structure determination by combining X-ray rietveld refinement, 1H MAS NMR FTIR and XANES spectroscopy.

Ion exchange of the sodium hydro sodalites [Na3(H2O)4]2-[Al3Si3O12]2 [Na4(H3O2)]2[Al3Si3O12]2 and [Na4(OH)]2[Al3Si3O12]2 with aqueous Pb(NO3)2 solutions yielded, whichever reactant sodalite phase was used, the same lead hydro sodalite, [Pb2(OH)-(H2O)3]2[Al3Si3O12]2. Thus, in the case of the non-basic reactant [Na3(H2O)4]2-[Al3Si3O12]2 an overexchange occurs with respect to the number of nonframework cationic charges. Rietveld structure refinement of the lead hydro sodalite based on powder X-ray diffraction data (cubic, a = 9.070 A, room temperature, space group P43n) revealed that the two lead cations within each polyhedral sodalite cage form an orientationally disordered dinuclear [Pb2(micro-OH)(micro-H2O)(H2O)2]3+ complex. Due to additional lead framework oxygen bonds the coordination environment of each metal cation (CN 3+3) is approximately spherical, and clearly the lead 6s electron lone pair is stereochemically inactive. This is also suggested by the absence of a small peak at 13.025 keV, attributed in other Pb2+-O compounds to an electronic 2p-6s transition, in the PbL3 edge XANES spectrum. 1H MAS NMR and FTIR spectra show that the hydrogen atoms of the aqua hydroxo complex (which could not be determined in the Rietveld analysis) are involved in hydrogen bonds of various strengths.

Heteronetwork clathrates with three-dimensional mixed silicate–water host frameworks and channel systems

X-Ray structure analysis reveals that in the crystalline silicate hydrates with the approximate chemical compositions [NPhMe3]6[Si8O18(OH)2]·38.7H2O and [NBnMe3]8[Si8O20]·53.6H2O (Bn = benzyl) cube-shaped octameric silicate anions and water molecules are linked via hydrogen bonds to form 3D mixed anionic host framework with channel systems; the interionic O ⋯ CH3(N) anion-cation interactions observed in the heteronetwork clathrates are of particular interest with regard to a very recently proposed mechanism for the formation of mesoporous silicate materials (M41S).