High-connectivity networks and hybrid inorganic rod materials built from potassium and rubidium p-halide-substituted aryloxides.

A series of complex networks have been synthesized from the association of potassium and rubidium p-halide-substituted aryloxides using 1,4-dioxane molecules as neutral linkers. The crystalline polymers [(4-F-C6H4OK)6 x (dioxane)4]infinity (1), [(4-I-C6H4OK)6 x (dioxane)6]infinity (2), and [(4-I-C6H4ORb)6 x (dioxane)6]infinity (3) are built from discreet, hexameric M6O6 aggregates. Compound 1 forms an unusual 16-connected framework involving both K-F and K-O(diox) interactions. Each hexamer connects to eight neighboring aggregates through double-bridging contacts, resulting in a body-centered cubic (bcu) topology. Compounds 2 and 3 are isostructural, 12-connected networks, where each aggregate utilizes six dioxane double bridges to form primitive cubic (pcu) nets. In contrast, the complexes [(4-Cl-C6H4OK)3 x (dioxane)]infinity (4), [(4-Br-C6H4OK)2 x (dioxane)0.5]infinity (5), and [(4-Br-C6H4ORb)5 x (dioxane)5]infinity (6) are built from one-dimensional (1D) inorganic rods composed solely of M-O(Ar) interactions. The extended structures of both 4 and 5 can be described as pcu nets, where parallel 1D inorganic pillars are connected through dioxane bridges. Compound 6 is also composed of parallel 1D inorganic rods, but in this instance the coordinated dioxane molecules do not bridge, resulting in isolated, close-packed chains in the solid state.

Manipulation of molecular aggregation and supramolecular structure using self-assembled lithium mixed-anion complexes.

A set of zero-, one-, two-, and three-dimensional materials have been synthesized by systematically varying the stoichiometry of the two components 2,4,6-Me3-C6H2OLi (ArOLi) and Me2N(CH2)(2)OLi (ROLi) within single aggregates, while using 1,4-dioxane (diox) as a ditopic linker. The homoleptic complex [{(ArOLi)4 x (diox)2} superset3(diox)](infinity) 1 forms a 3D diamondoid extended structure, where Li4O4 cubanes act as tetrahedral nodes. Attempts to rationally alter the dimensionality of the network through the sequential replacement of ArOLi vertices by potentially chelating ROLi units have succeeded. The mixed-anion complexes [{(ROLi)(ArOLi)3 x (diox)(1.5)} superset1/2(C6H14)](infinity) 2 and [(ROLi)4(ArOLi)2 x (diox)](infinity) 4 , adopt 2D hexagonal net and 1D chain structures respectively. Furthermore, the two complexes [{(ROLi)3(ArOLi)3 x (diox)(0.5)}(C6H14)](infinity) 3 and [(ROLi) 5(ArOLi) x (diox)(0.5)](infinity) 5 both form unusual 0D molecular dumbbell structures in the solid state. Incorporation of multiple ROLi units in the mixed-anion complexes not only results in reducing the number of possible sites for polymer extension through chelation, but also changes the aggregation state of the building block from tetrametallic Li4O4 units to hexametallic Li6O6 units.

High-connectivity networks: characterization of the first uninodal 9-connected net and two topologically novel 7-connected nets.

Ring and cage aggregates containing the large alkali metals potassium or rubidium have proven to be excellent building blocks for the creation of high-connectivity nets, as demonstrated by their use as septahedral and nonahedral nodes in synthesis of two new types of 7-connected nets and the first ever example of a 9-connected net.

X-ray and neutron diffraction studies of water-encapsulated inside potassium aryloxide aggregates: complementary host-guest stabilization of mono- and dihydrated cages.

The controlled hydrolysis of potassium 2-tert-butylphenoxide or 2-isopropylphenoxide leads to the unexpected encapsulation of the water inside K6O6 hexameric drum aggregates. Encapsulation of the neutral molecules is enabled in these instances through the formation of strong hydrogen bonds and dative interactions between the host and guest.

Organometallic polymers assembled from cation-pi interactions: use of ferrocene as a ditopic linker within the homologous series [{(Me3Si)2NM}2.(Cp2Fe)]infinity (M=Na, K, Rb, Cs; Cp=cyclopentadienyl).

Addition of ferrocene to solutions of alkali metal hexamethyldisilazides M(HMDS) in arenes (in which M=Na, K, Rb, Cs) allows the subsequent crystallization of the homologous series of compounds [{(Me(3)Si)(2)NM}(2) (Cp(2)Fe)](infinity) (1-4). Similar reactions using LiHMDS led to the recrystallization of the starting materials. The crystal structures of 1-4 reveal the formation of one-dimensional chains composed of dimeric [{M(HMDS)}(2)] aggregates, which are bridged through neutral ferrocene molecules by eta(5)-cation-pi interactions. In addition, compounds 3 and 4 also contain interchain agostic M--C interactions, producing two-dimensional 4(4)-nets. Whereas 1 and 2 were prepared from toluene, the syntheses of 3 and 4 required the use of tert-butylbenzene as the reaction media. The attempted crystallization of 3 and 4 from toluene resulted in formation of the mixed toluene/ferrocene solvated complexes [{(Me(3)Si)(2)NM)(2)}(2) (Cp(2)Fe)(x)(Tol)(y)](infinity) (in which M=Rb, x=0.6, y=0.8, 5; M=Cs, x=0.5, y=1, 6). The extended solid-state structures of 5 and 6 are closely related to the 4(4)-sheets 3 and 4, but are now assembled from a combination of cation-pi, agostic, and pi-pi interactions. The charge-separated complex [K{(C(6)H(6))(2)Cr}(1.5)(Mes)][Mg(HMDS)(3)] (15) was also structurally characterized and found to adopt an anionic two-dimensional 6(3)-network through doubly eta(3)-coordinated bis(benzene)chromium molecules. DFT calculations at the B3 LYP/6-31G* level of theory indicate that the binding energies of both ferrocene and toluene to the M(HMDS) dimers increases in the sequence Li

Kinetics and mechanism of ketone enolization mediated by magnesium bis(hexamethyldisilazide).

Magnesium bis(hexamethyldisilazide), Mg(HMDS)(2), reacts with substoichiometric amounts of propiophenone in toluene solution at ambient temperature to form a 74:26 mixture of the enolates (E)- and (Z)-[(HMDS)(2)Mg(2)(mu-HMDS){mu-OC(Ph)=CHCH(3)}], (E)-1 and (Z)-1, which contain a pair of three-coordinate metal centers bridged by an amide and an enolate group. The compositions of (E)-1 and (Z)-1 were confirmed by solution NMR studies and also by crystallographic characterization in the solid state. Rate studies using UV-vis spectroscopy reveal the rapid and complete formation of a reaction intermediate, 2, between the ketone and magnesium, which undergoes first-order decay with rate constants independent of the concentration of excess Mg(HMDS)(2) (DeltaH++ = 17.2 +/- 0.8 kcal/mol, DeltaS++ = -11 +/- 3 cal/mol.K). The intermediate 2 has been characterized by low-temperature (1)H NMR, diffusion-ordered NMR, and IR spectroscopy and investigated by computational studies, all of which are consistent with the formulation of 2 as a three-coordinate monomer, (HMDS)(2)Mg{eta(1)-O=C(Ph)CH(2)CH(3)}. Further support for this structure is provided by the synthesis and structural characterization of two model ketone complexes, (HMDS)(2)Mg(eta(1)-O=C(t)Bu(2)) (3) and (HMDS)(2)Mg{eta(1)-O=C((t)Bu)Ph} (4). A large primary deuterium isotope effect (k(H)/k(D) = 18.9 at 295 K) indicates that proton transfer is the rate-limiting step of the reaction. The isotope effect displays a strong temperature dependence, indicative of tunneling. In combination, these data support the mechanism of enolization proceeding through the single intermediate 2 via intramolecular proton transfer from the alpha carbon of the bound ketone to the nitrogen of a bound hexamethyldisilazide.

Use of tetrameric cubane aggregates of lithium aryloxides as secondary building units in controlling network assembly.

Pre-aggregation of lithium aryloxides into tetrahedral arrangements followed by crystallization with the divergent Lewis base dioxane results in the preparation of three types of coordination polymers: zig-zag chains, (6,3) sheets, and diamondoid lattices.