New Adducts of Triphenylboroxine and Bis-pyridines: Syntheses and Crystal Structures of (Ph3B3O3)(η 1-4,4′-bpy), (Ph3B3O3)2(μ-4,4′-bpy) and (Ph3B3O3)2(μ-bpe)

Abstract

The treatment of phenylboronic acid PhB(OH) 2 with 4,4 0 -bipyridine (4,4 0 -bpy) in a 3:1 ratio afforded adduct [(Ph 3 B 3 O 3 )(g 1 -4,4 0 -bpy)] (1), whereas the reaction of PhB(OH) 2 with 4,4 0 -bpy in a 6:1 ratio afforded adduct [(Ph 3 B 3 O 3 ) 2 (l-4,4 0 -bpy)] (2). Similarly, the reaction of PhB(OH) 2 with trans-1,2-bis(4-pyridyl)ethylene (bpe) in a 6:1 ratio gave bpe bridged adduct [(Ph 3 B 3 O 3 ) 2 (l-bpe)] (3). The crystal structures of 1ÁC 6 H 6 , 2Á2C 7 H 8 , 2ÁC 6 H 14 , and 3ÁC 6 H 6 , along with other spectroscopic properties are reported. The weak NÁÁÁH-C hydrogen-bonds exist in the one-dimensional chains of 1ÁC 6 H 6 . Graphical Abstract Treatment of PhB(OH) 2 with 4,4 0 -bpy or bpe under different conditions afforded three new adducts [(Ph 3 B 3 O 3 )(g 1 -4,4 0 -bpy)] (1), [(Ph 3 B 3 O 3 ) 2 (l-4,4 0 -bpy)] (2) and [(Ph 3 B 3 O 3 ) 2 (l-bpe)] (3) through the B-N dative bonds.

Structural Induction via Solvent Variation in Assemblies of Triphenylboroxine and Piperazine—Potential Application as Self-Assembly Molecular Sponge

“…The N→B bond distances in 1a·THF (1.702 and 1.707 Å) are practically identical to those in 1a·Acetone (1.694 and 1.699 Å). For comparison, N→B bond distances for monoadducts (ArBO) 3 L and 1:2 adducts (PhBO) 3 ·2L with Ar = aryl and L = aliphatic or aromatic N-donor ligand have values in the range of 1.61–1.67 Å and 1.64–1.74 Å, respectively. − ,− , The coordination geometry around the sp 3 boron atoms in 1a·THF and 1a·Acetone corresponds to a distorted tetrahedron with bond angles in the range of 101.3–115.7°. The third noncoordinated boron atom has a trigonal-planar geometry with angles between 117.6° and 122.9°.…”

“…For comparison, N→B bond distances for monoadducts (ArBO) 3 L and 1:2 adducts (PhBO) 3 •2L with Ar = aryl and L = aliphatic or aromatic N-donor ligand have values in the range of 1.61−1.67 Å and 1.64−1.74 Å, respectively. [65][66][67][68][69][70][71][72][73][79][80][81][82][83]91 The coordination geometry around the sp 3 The propagation of neighboring chains in compounds 1a• THF and 1a•Acetone generates pseudocavities, which are filled by the corresponding solvent (Figure 2). In both cases, the oxygen atom of the solvent is involved in the formation of asymmetric 4c).…”

“…In both cases, the solvent molecules are located in the cavities formed between the N→B complexes. Similar 2:1 adducts {(PhBO) 3 L(PhBO) 3 } have been reported for L = 4,4′bipyridine, 82 1,2-di(4-pyridyl)ethylene, 82 hexamethylenetetr- amine, 81 1,4-diazabicyclo[2.2.2]octane, 58 p-phenylenediamine, 58 and trans-1,4-cyclohexanediamine. 91 N→B Adducts Formed from Halogenated Solvents.…”

“…Derivatives of boronic acids have been widely used as building blocks in the development of ordered structures to generate macrocycles, cages, calixarene systems, or two- and three-dimensional networks. − Boroxines are anhydrides of organoboronic acids and contain a heterocyclic B 3 O 3 ring and have been also successfully applied as building blocks for macrocycles, molecular cages, polymers, and three-dimensional networks, − with applications in methane storage, electronic , and optical devices, and as a source of aryl and vinyl groups. , Additionally, they can easily form supramolecular systems due to their ability to generate N→B coordinative bonds with organic amines . Although the boroxine B 3 O 3 ring is theoretically capable of coordinating up to three nitrogen atoms, it is well-known that the most stable adducts involve the interaction with only one nitrogen atom per ring, − as reflected in the number of structures reported with this stoichiometric composition. − In contrast, triarylboroxine species carrying aryl rings with amine substituents in the ortho position represent the few examples, in which a B 3 O 3 ring is coordinated to more than one nitrogen atom. − The number of 1:2 boroxine/amine adducts is limited and 1:3 adducts with independent organic amines are currently unknown. − With the interest in organoboron compounds and their applications in supramolecular chemistry taken into account, the study of the susceptibility of these assemblies toward the properties of the solvent is relevant, mainly because the lability of the N→B bond in the corresponding adducts is well-known …”

Mechanochemical Mediated Coexistence of B←N Coordination and Hydrogen Bonding

“…As a building block in a supramolecular synthesis, the B(OH) 2 group of an aryl BA can react to participate in hydrogen bonds [12][13][14][15][16][17][18] (i.e., OÀ H•••X) and/or B-coordination (i.e., BÀ X), [5,[18][19][20][21][22][23] depending on reaction conditions. Thus, hydrogen-bonded cocrystals of boronic acids will typically form from solution at room temperature [14][15][16][17] while boroxines typically form with addition of heat [23][24][25] or added reaction time. [22] Moreover, the dual nature of BAs in participating in different types of noncovalent bonds can effectively enable BAs to provide information on chemical environment in a dynamic selfassembly process.…”