A series of crystalline nonmetal borate compounds was prepared by reactions of linear α,ω-diaminoalkanes, H2N(CH2) n NH2 (n = 5−12), with excess boric acid in aqueous solution. These simple reagents self-assemble in water to form complex ordered structures. The products were characterized by a combination of elemental, thermal, and X-ray diffraction analyses as well as single-crystal X-ray diffraction studies. In each case except for n = 7 and 12, a bis(pentaborate) product of general formula [H3N(CH2) n NH3][B5O6(OH)4]2 (1, 2, 4−7) was obtained in good yield. When n = 12, the product, [H3N(CH2)12NH3][B5O6(OH)4]2·4H2O (8), contained interstitial water. When n = 7, a product of composition [H3N(CH2) 7 NH3][B8O10(OH)6]·2B(OH)3 (3) was obtained, containing an unusual octaborate anion and interstitial boric acid. The borate anions form hydrogen-bonded supramolecular anionic frameworks that host alkyldiammonium dications. These cations contribute to hydrogen bonding and arrange either extended linearly or folded to varying degrees across channels. This study reveals an interplay between the anionic borate host and the cationic guest in which the nature of the cation controls the borate framework structure, which in turn influences cation conformation.

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Borate compounds in which boron is bound only to oxygen have considerable mineralogical and industrial importance. These contain anionic components composed of BO 3 and BO 4 groups that may link together by sharing oxygen atoms to form isolated rings and cages or polymerize into infinite chains, sheets, and networks. Many examples of isolated boron oxoanions containing one to six borons exist in mineral and synthetic borates. However, isolated boron oxoanions having more than six borons are rare and no previous examples have nine borons. 2 This communication describes the synthesis and structural characterization of crystalline guanidinium and imidazolium borates, [C(NH 2 ) 3 ] 3 [B 9 O 12 (OH) 6 ] (I) and [C 3 H 5 N 2 ] 3 [B 9 O 12 (OH) 6 ] (II), containing the first examples of the isolated nonaborate anion, [B 9 O 12 (OH) 6 ] 3-. These borates have resolved oxide formulas [C(NH 2 ) 3 ] 2 O‚3B 2 O 3 ‚2H 2 O and [C 3 H 5 N 2 ] 2 O‚3B 2 O 3 ‚2H 2 O. Isolated boron oxoanions are found in the commercially significant metaborates ([B(OH) 4 ] -), tetraborates ([B 4 O 5 (OH) 4 ] 2-), and pentaborates ([B 5 O 6 (OH) 4 ] -), as well as in triborates ([B 3 O 3 (OH) 4 ] -and [B 3 O 3 (OH) 5 ] 2-). 3 Also, some mineral and synthetic borates contain the isolated hexaborate anion, [B 6 O 7 (OH) 6 ] 2-. 2 The mineral ammonioborite contains an unusual example of a large isolated anion, [B 15 O 20 (OH) 8 ] 3-. 2 Polyborate anions can be regarded as products of varying degrees of neutralization of orthoboric acid, B(OH) 3 , with a strong base in relatively concentrated aqueous solution. The [B 3 O 3 (OH) 4 ] -and [B 6 O 7 (OH) 6 ] 2-anions, as well as the [B 9 O 12 (OH) 6 ] 3-anion described herein, can all be viewed as products of a 1 / 3 neutralization with strong base of boric acid to [B(OH) 4 ] -. At least three crystalline binary guanidinium borates exist. Guanidinium tetraborate, [C(NH 2 ) 3 ] 2 [B 4 O 5 (OH) 4 ]‚2H 2 O (III), was reported as early as 1921, 4 and brief references are made to guanidinium pentaborates, including [C(NH 2 ) 3 ][B 5 O 6 (OH) 4 ]‚2H 2 O (IV). 5 We have recently found that the novel guanidinium nonaborate I crystallizes in the [C(NH 2 ) 3 ] 2 O-B 2 O 3 aqueous system at temperatures above ca. 45°C at B 2 O 3 /[C(NH 2 ) 3 ] 2 O mole ratios (defined as q) greater than ca. 2.5 over a range of concentrations. Tetraborate III crystallizes at lower temperatures or q values. At q > 5 either boric acid or guanidinium pentaborate IV crystallizes, depending on concentrations. Nonaborate I can be prepared by aqueous stoichiometric or near-stoichiometric reaction of guanidinium carbonate with boric acid: 6Alternatively, I can be prepared by reaction of guanidinium salts with borax and boric acid under appropriate conditions. 7 Nonaborate I exhibits temperature-dependent stability in water contact. At 20°C, an aqueous slurry of I converts to tetraborate III and boric acid in about 1 day. At elevated temperatures, I is stable in aqueous slurry and can be recrystallized from water. Nonaborate I can also be pre...

The nonmetal borate [H3N(CH2)7NH3][B7O9(OH)5].H2O (1) was prepared via a neat reaction of 1,7-diaminoheptane with excess boric acid under mild nonhydrothermal conditions. Single-crystal X-ray characterization of 1 revealed a new isomer of the heptaborate anion, B7O9(OH)5(2-). The heptaborate anion in 1 is comprised of four fused (BO)3 rings sharing three four-coordinate boron atoms and a single three-coordinate oxygen atom. This anion is a structural isomer of another recently described heptaborate anion, consisting of a chain of three (BO)3 rings. Compound 1 crystallized in the triclinic space group P1 with a=9.3266(17) A, b=10.1222(19) A, c=10.847(2) A, alpha=89.422(2) degrees, beta=82.349(2) degrees, gamma=75.158(2) degrees, V=980.7(3) A3, and Z=2.

A new synthetic methodology for adding carbon-based nucleophiles to the carbocyclic ring of quinolines has been developed, based on the electron-deficient bonding of the C(8) carbon and the protective coordination of the nitrogen atom to the metal core in the complexes Os 3 (CO) 9 (µ 3 -η 2 -C 9 H 5 (R)N)(µ-H), 1a-1h. These compounds react with a wide range of carbanions (e.g., R′Li) to give the nucleophilic addition products Os 3 (CO) 9 (µ 3 -η 3 -C 9 H 7 (5-R′)N)(µ-H), 2a-2l, and Os 3 (CO) 9 (µ 3 -η 3 -C 9 H 6 (3-, 4-, or 6-R)(5-R′)N)(µ-H), 3b-3g, after quenching with trifluoroacetic acid, in isolated yields of 25-86%. In the 6-substituted derivatives, this addition is stereoselective, forming only the cis-diastereomer. In the case the 6-chloro derivative, a second product is obtained, Os 3 (CO) 9 (µ 3 -η 2 -C 9 H 5 (6-Cl)(5-C(CH 3 ) 2 CN)N)(µ-H) 2 , 4, the result of protonation at the metal core and rearrangement of the carbocyclic ring. The trans-diastereomer of the 6-substituted derivatives can be obtained by quenching the intermediate anion of the unsubstituted complex with (CH 3 O) 2 SO 2 or acetic anhydride. Nucleophilic addition to the 5-chloro complex occurs across the 3,4-bond to give Os 3 (CO) 9 (µ 3η 2 -C 9 H 6 (5-Cl)(4-C(CH 3 ) 2 CN)N)(µ-H), 5. The addition products, types 2 and 3, can be rearomatized by reaction with diazobicyclononane (DBU)/dichlorodicyanoquinone (DDQ) or by reaction of the intermediate anion with trityl cation or DDQ. The resulting rearomatized complexes can be cleanly cleaved from the cluster by heating in acetonitrile under a CO atmosphere, yielding the functionalized quinoline and Os 3 (CO) 12 as the only two products. Solid structures of cis-3e, trans-3e, 4, and 5 are reported.

The thermal decomposition of guanidinium tetraborate, pentaborate, and nonaborate has been characterized under nitrogen and ammonia atmospheres, and conditions have been defined for bulk powder and aqueous aerosol transformations of these precursors to boron nitride (BN). The bulk pyrolyses under ammonia (600-1400 °C) produce micrometer-and sub-micrometer-sized platelet morphology particles with oxygen contents of 3-18 wt. %. Subsequent pyrolysis of these powders at 1600 °C under NH 3 reduces the oxygen contents to <1 wt. %. Pyrolysis of aqueous aerosols containing the guanidinium borates gives submicrometer spherical morphology BN particles. The chemistry and processing of guanidinium borates are compared with the behavior of alternative precursors.

The triborate and pentaborate compounds 3-hydroxy-2,2-dimethylpropylammonium triborate(1+), [HOCH2C(CH3)2NH3][B3O3(OH)4] (1), and 2-hydroxyethylammonium pentaborate(1-), [HOCH2CH2NH3][B5O6(OH)4].H2O (2), were prepared by crystallization from concentrated aqueous boric acid solutions containing the respective alcoholamines at a boric acid-alcoholamine mole ratio of 3.33:1.00. Compound 1 crystallized in the triclinic space group P1 with a = 5.9595(9) A, b = 6.3024(9) A, c = 15.594(2) A, alpha = 91.218(2) degrees , beta = 91.138(2) degrees , gamma = 118.034(2) degrees , V = 516.56(13) A (3), and Z = 2; 2 crystallized in the monoclinic space group P2 1/ n with a = 11.2469(8) A, b = 9.5091(6) A, c = 11.5422(8) A, beta = 90.175(1) degrees , V = 1234.41(15) A (3), and Z = 4. Compound 1 contains a rare example of a structurally characterized hydroxyl-hydrated triborate monoanion. Comparisons are made with other known examples of this anion.

Structure Structure D 2000 Structural Characterization and Chemistry of the Industrially Important Zinc Borate, Zn[B 3 O 4 (OH) 3 ]. -As revealed by single crystal XRD, the title compound crystallizes in the monoclinic space group P2 1 /n with Z = 4. The structure is a complex network consisting of infinite polytriborate chains cross-linked by coordination with Zn and further integrated by hydrogen bonding. The new structural information leads to a revision of the chemical formula 2ZnO·3B 2 O 3 ·3.5H 2 O, typically used to describe this material as an article of commerce, to 2ZnO·3B 2 O 3 ·3H 2 O. -(SCHUBERT*, D. M.; ALAM, F.; VISI, M. Z.; KNOBLER, C. B.; Chem. Mater. 15 (2003) 4, 866-871;