Synthesis and characterization of a novel eight-membered cyclo-1,3,3,5,7,7-hexaphenyl-1,5-dibora-3,7-disiloxane and 4,4ˈ-bipyridine, 1D adduct European Journal of Chemistry 15 (3) (2024) 232-238 European Journal of Chemistry ISSN 2153-2249 (Print) / ISSN 2153-2257 (Online) – Copyright © 2024 The Authors – Atlanta Publishing House LLC – Printed in the USA. This work is published and licensed by Atlanta Publishing House LLC – CC BY NC – Some Rights Reserved. https://dx.doi.org/10.5155/eurjchem.15.3.232-238.2545 European Journal of Chemistry View Journal Online View Article Online Synthesis and characterization of a novel eight-membered cyclo-1,3,3,5,7,7- hexaphenyl-1,5-dibora-3,7-disiloxane and 4,4ˈ-bipyridine, 1D adduct Okpara Sergeant Bull *, Chioma Don-Lawson , and Ugo Nweke-Maraizu Department of Chemistry, Faculty of Science, Rivers State University, Nkpolu-Oroworukwo, Port Harcourt, PMB 5080, Nigeria * Corresponding author at: Department of Chemistry, Faculty of Science, Rivers State University, Nkpolu-Oroworukwo, Port Harcourt, PMB 5080, Nigeria. e-mail: bull.okpara@ust.edu.ng (O.S. Bull). 10.5155/eurjchem.15.3.232-238.2545 Received: 04 March 2024 Received in revised form: 11 May 2024 Accepted: 12 June 2024 Published online: 30 September 2024 Printed: 30 September 2024 Simple adducts of cyclo-diboradisiloxanes (Lewis acid) and amines (Lewis base) have been reported in the literature. However, the method for the synthesis of an 8-membered cyclo- diboratetrasiloxane, as well as its adducts, was modified in this report to save cost and achieve new results. In the literature, the synthesis of cyclo-1,3,3,5,7,7-hexaphenyl-1,5- dibora-3,7-disiloxane (Ph6B2Si2O4) (3) has been reported using diphenylsilanediol and phenylboronic acid and a Dean-Stark apparatus for the removal of water. However, in this study, molecular sieves were used for the facile removal of water, and the crude product recrystallized from diethyl ether and petroleum ether (3:1 ratio) to give compound 3. Compound 3 was reacted with 4,4’-bipyridine in a mixture of diethyl ether and petroleum ether solvents at reflux to give a 1D polymer [Ph6B2Si2O4]·L1 (4). Furthermore, compound 4 was characterized with various characterization methods such as single-crystal XRD, nuclear magnetic resonance, and FT-IR spectroscopy. The single crystal X-ray diffraction studies shows that the title compound crystalizes in the triclinic crystal system in the centrosymmetric space group P-1, a = 10.9372(4) Å, b = 18.4221(6) Å, c = 19.4697(6) Å, α = 70.533(3)°, β = 86.476(3)°, γ = 88.517(3)°, V = 3691.6(2) Å3, Z = 2, T = 173.0 K, μ(MoKα) = 0.122 mm-1, Dcalc = 1.204 g/cm3, 21463 reflections measured (5.196° ≤ 2Θ ≤ 56.45°), 14525 unique (Rint = 0.0185, Rsigma = 0.0483) which were used in all calculations, the final R1 was 0.0721 (I > 2σ(I)) and wR2 was 0.2143 (all data) with the 8-membered cyclo-1,3,3,5,7,7- hexaphenyl-1,5-dibora-3,7-disiloxane (Ph6B2Si2O4) (3) configuration. 1D Polymer 4,4ˈ-Bipyridine Diphenylsilanediol Phenylboronic acid Eight-membered ring Cyclodiboratetrasiloxane Cite this: Eur. J. Chem. 2024, 15(3), 232-238 Journal website: www.eurjchem.com 1. Introduction Inorganic cyclic systems such as borasiloxanes (B-O-Si), in addition to being highly attractive in appearance, also serve as important systems with a wide range of applications arising from their fascinating magnetic and optical properties, electronic structures, potential quasi-aromatic character, and the ability to form extended π-π intra- and intermolecular interactions [1]. In principle, rings of the general formula BnSimOn+m, will have 2(n + m) π-electrons available for deloca- lization from the oxygen lone pairs. If n + m = 3, the Hückel criterion of 6 π-electrons is met, while if n + m = 4, an anti- aromatic 8 π-electron count results [2]. Furthermore, the ring systems (B-O-Si) and (Si-O-Si) have been used as molecular building blocks in the construction of metal-organic frameworks (MOFs) [3-9], covalent organic frameworks (COFs) [3,10,11] and other supramolecular compounds such as silsesquioxanes [10]. Compounds containing Si-O-B and O-B-O abound in the literature [12], and the Si-O, B-O, and C-O bond energies are 452, 536 and 358 kJ/mol, respectively. Thus, the Si-O and B-O bonds are stronger than the typical C-O bond energy. A good number of these compounds possess and display unusual high elasticity when a stress is suddenly applied, as well as high plasticity when the stress is applied slowly [13]. These compounds containing Si-O-B and O-B-O exist in the form of metaboronic acid, six-, eight-, or ten- member cages, cyclo-borosiloxane derivatives, or borosilicate cages, as well as large rings as shown in Figure 1 [12,14]. Borosilicate scaffolds have promising applications as building blocks in supramolecular chemistry. For example, Hunt et al. [15] and Pascu et al. [16] reported the use of an 8- membered borosilicate cage whose nodes were used for the synthesis of a 3-D system (COF-202) and macrocycles, respectively. Liu et al. [17] used the same principle for the synthesis of π-extended polymeric borosilicate cages used as sensors for volatile organic amines. Gopalakrishnan et al. [18] reported the synthesis, structure, photophysical, and other calculations for a series of eight-membered cyclic-borasil- oxanes wherein the crystal packing pattern displayed noncovalent interactions. Recently, the synthesis of cage-like cyclic borosilicates based on boronic acid and the potential application in the assembly of triphenylboroxine and pipera- zine was reported [19,20]. Despite the myriad of applications for borosilicates and borosilicate adducts, only a few synthetic strategies for cyclic and cage-like molecular borosilicates and adducts are known. The reason for this may be mainly due to (i) the few comer- cially available silanols, (ii) the structural modifications of these compounds are difficult, and (iii) problems associated with stability [19]. ABSTRACT RESEARCH ARTICLE KEYWORDS https://dx.doi.org/10.5155/eurjchem.15.3.232-238.2545 https://www.eurjchem.com/ https://dx.doi.org/10.5155/eurjchem.15.3.232-238.2545 mailto:bull.okpara@ust.edu.ng http://www.eurjchem.com/ https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.15.3.232-238.2545&domain=pdf&date_stamp=2024-09-30 Bull et al. / European Journal of Chemistry 15 (3) (2024) 232-238 233 2024 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.15.3.232-238.2545 Si O O R' R' B B O O R R Si R' R'Si O R' R' B O R Si R' R'O (i) (ii) B O R B O R B RO (iii) L Si O O B B O O R Si (iv) L R' R' R'R' R (v) (vi) R, R' = Alkyl, aryl L = Donor SiO O Si OBO Si O Si R R' R' R' R' R' R' R' R' O Si O Si O B OSiO Si O B R' R' RR' R' R R' R' R' R' Figure 1. Structures of (i) 6-membered cyclo-boradisiloxane; (ii) 8-membered cyclo-diboradisiloxane; (iii) 1:1 adduct of a boroxine; (iv) 1:1 adduct of a cyclo- diboradisiloxane; (v) 10-membered cyclo-diboratetrasiloxane; (vi) 12-membered cyclo-diborahexasiloxane. Scheme 1. Preparation of (Ph6B2Si2O4) (3) and [Ph6B2Si2O4]·L1 (4) adduct. The basic methods used in the synthesis of these borasiloxanes rings involve the cyclocondensation reaction of appropriate organoboronic acids and Si-containing precursors such as dihydroxysiloxanes, diethoxysilanes, and α,ω-dihydro- siloxanes as well as the condensation of dichlorophenylborane with dihydroxysilanes [12,21,22]. Solvents used include dry toluene, triethylamine, sodium-dried-benzene, or a mixture of solvents under a nitrogen atmosphere in which water is continuously removed using a Dean-Stark apparatus because these reactions are readily reversible. In this study, we report the synthesis and characterization of an eight-membered cyclodiboradisiloxane ring in which the boron atoms are tricoordinate (Lewis acid) and its further reaction with a 4,4’- bipyridine ligand (Lewis base) to give further coordination adducts possessing interesting properties [23]. In the literature, the synthesis of cyclo-1,3,3,5,7,7-hexa- phenyl-1,5-dibora-3,7-disiloxane (Ph6B2Si2O4) (3) has been reported using diphenylsilanediol (1) and phenylboronic acid (2) and a Dean-Stark apparatus for the removal of water, with a reported 87% yield of compound 3 [2]. However, in the current research, molecular sieves were used for the removal of water and after the study, compound 3 was reacted with 4,4’- bipyridine to give a 1D polymer (4) adduct as shown in Scheme 1. Thus, the purpose of this research is to synthesis this eight- membered ring, characterize the eight-membered ring and then ligate it with a 4,4’-bipyridine ligand to give further coordi- nation adducts with extended π-π stacking interactions. 2. Experimental 2.1. Chemicals and reagents All chemicals, reagents, and solvents were purchased from Sigma-Aldrich or Alfa-Aesar and used as received unless otherwise stated. Molecular sieves (1.6 mm rods and 0.4 nm pores) were preheated to dryness in the oven at 120 °C for two weeks prior to use. 234 Bull et al. / European Journal of Chemistry 15 (3) (2024) 232-238 2024 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.15.3.232-238.2545 Table 1. Crystal data and structure refinement for [Ph6B2Si2O4]·L1 (4). Compound [Ph6B2Si2O4]·L1 (4) Empirical formula C69H57B3N3O6Si3, 0.6(C10H8N2), 1.4(C4H10O) Formula weight (g/mol) 1338.35 Temperature (K) 173.0 Crystal system Triclinic Space group P-1 a, (Å) 10.9372(4) b, (Å) 18.4221(6) c, (Å) 19.4697(6) α (°) 70.533(3) β (°) 86.476(3) γ (°) 88.517(3) Volume (Å3) 3691.6(2) Z 2 ρcalc (g/cm3) 1.204 μ (mm-1) 0.122 F(000) 1410.0 Crystal size (mm3) 0.58 × 0.33 × 0.2 Radiation MoKα (λ = 0.71073) 2Θ range for data collection (°) 5.196 to 56.45 Index ranges -14 ≤ h ≤ 14, -21 ≤ k ≤ 24, -24 ≤ l ≤ 21 Reflections collected 21463 Independent reflections 14525 [Rint = 0.0185, Rsigma = 0.0483] Data/restraints/parameters 14525/293/909 Goodness-of-fit on F2 1.033 Final R indexes [I≥2σ (I)] R1 = 0.0721, wR2 = 0.1929 Final R indexes [all data] R1 = 0.0963, wR2 = 0.2143 Largest diff. peak/hole (e.Å-3) 1.12/-0.90 2.2. Instrumentation 1H, 13C{1H}, 11B{1H}, and 29Si{1H} NMR spectra were recorded on Bruker Avance III HD 400 MHz or 500 MHz spectrometers in CDCl3 solvent unless otherwise stated. The chemical shifts (δ) for 1H and 13C{1H}, 29Si{1H}, and 11B{1H} are quoted in ppm with reference to Me4Si and BF3OEt2. The coupling constants are reported in Hz. Infrared spectra were obtained on a Perkin Elmer Spectrum 100 FTIR Spectrometer operating in ATR mode. 2.3. Synthesis 2.3.1. Preparation of Ph6B2Si2O4 (3) Diphenylsilanediol (1) 1.082 g (5.0 mmol) was mixed with 0.609 g (5.0 mmol) of phenylboronic acid (2) in dry toluene (50 mL) and 0.5 g of molecular sieves in a round bottom flask containing a magnetic stirrer bar. The mixture was refluxed under N2 for 20 h. Thereafter, the round bottom flask and its contents were cooled to room temperature. The cooled reaction mixture was filtered and the filtrate collected. The molecular sieves were washed with dry toluene (3×25 mL). The filtrates were combined and concentrated under reduced pressure, and the solid residue was recrystallized from diethyl ether and petroleum ether (3:1 ratio) to give compound 3, 1.30 g, 86% (Lit. 87% [2]); M.p.: 162-163 °C (Lit. 161-162 °C [2]). Cyclo-1, 3, 3, 5, 7, 7-hexaphenyl-1, 5-dibora-3, 7-disiloxane: Color: White. Yield: 86%. M.p.: 162.0-163.0 °C. 1H NMR (500 MHz, CDCl3, δ, ppm): 7.31-7.54 (m, 18H, m,p-C6H5), 7.73-7.75 (m, 8H o-C6H5Si), 8.08-8.10 (m, 4H, o-C6H5B). 13C NMR (125 MHz, CDCl3, δ, ppm): 127.93, 128.06, 130.60, 131.74, 133.40, 134.12, 135.65 (C6H5Si, C6H5B). 11B NMR (160 MHz, CDCl3, δ, ppm): 25.69. 29Si{1H} NMR (99 MHz, CDCl3, δ, ppm): -45.00. MS (70 eV, EI, m/z): 604 (M+), 527 (M-Ph)+, 423 (M-Ph-PhBO)+, 406 (M-Ph2SiO)+. FT-IR (ATR, ν, cm-1): 3023 (C-H aromatic), 1349 (B-O), 1307 (Si-C str.), 1071 (Si-O str.). 2.3.2. Preparation of [Ph6B2Si2O4]·L1 (4) In a round bottom flask, [Ph6B2Si2O4] (3), (0.25 g, 0.415 mmol) was added to 4,4’-bipyridine (L1) (0.065 g, 0.415 mmol) and a mixture of solvents (diethyl ether 21 mL and petroleum ether 7 mL). The mixture was heated at reflux while stirring for 4 h. The resultant solution was allowed to cool to room temperature followed by filtration. The filtrate was transferred to a vial, covered with perforated parafilm, and stored in the fumehood for slow evaporation of the solvent. Colourless crystals were obtained from the mixture of diethyl ether and petroleum ether solvents after 12 h to give compound 4, [Ph6B2Si2O4]·L1. Color: White. Yield: 84%. M.p.: 184-186 °C. FT- IR (ATR, ν, cm-1): 3067 (C-H aromatic), 1429 (B-O), 1324 (C-N), 1059 (Si-O str.). 1H NMR (500 MHz, CDCl3, δ, ppm): 7.32-7.56 (m, 18H, m, p-C6H5), 7.62-7.64 (m, 4H, m-C5H4N), 7.73-7.78 (m, 8H, o-C6H5Si), 8.09-8.17 (m, 4H, o-C6H5B), 8.80-8.82 (m, 4H, o-C5H4N). 13C NMR (125 MHz, CDCl3, δ, ppm): 149.96, 145.87, 135.36, 134.30, 134.10, 133.72, 131.32, 127.94, 127.94, 127.82, 121.59. 11B NMR (160 MHz, CDCl3, δ, ppm): 20.91. 29Si{1H} NMR (99 MHz, CDCl3, δ, ppm): -45.16. 3. Results and discussion The eight-membered borasiloxane compound 3 was characterized using standard analytical and spectroscopic methods. Compound 3 is a colorless crystalline solid and readily soluble in nonpolar organic solvents such as hexane and benzene. The 1H NMR spectrum of compound 3 shows well- resolved resonances with aromatic proton signals found within the range of δ 7.32-8.17 ppm, comparable to values reported in the literature [12,14,18]. The 13C{1H} NMR spectrum of compound 3 shows signals for aromatic carbons in the range of δ 127.93-135.65 ppm, which are also in agreement with the values in the literature [12,14,18]. The 11B{1H} NMR of compound 3 shows a broad singlet at δ 25.69 ppm, which is indicative of a single boron chemical environment. In the same way, the 29Si NMR of compound 3 showed a singlet at δ -45.00 ppm. Furthermore, the IR spectrum obtained from compound 3 showed strong absorption peaks in the regions: 3023 cm-1, νC-H; 1349 cm-1, νB-O; 1307 cm-1, νSi-C; 1071 cm-1, νSi-O [24]. Subsequently, compound 3 was treated with 4,4'-bipyridine (L1). Compound 4 crystallized in the triclinic unit cell with a space group of P-1. Crystallographic data, bond distance, and angle values are shown in Tables 1-3, respectively. Bull et al. / European Journal of Chemistry 15 (3) (2024) 232-238 235 2024 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.15.3.232-238.2545 Table 2. Selected bond lengths for [Ph6B2Si2O4]·L1 (4) *. Atom Atom Length, Å Atom Atom Length, Å Atom Atom Length, Å Atom Atom Length, Å B1 O2 1.436(4) O4 B5 1.437(4) Si7 C61' 1.907(7) O22 Si23 1.621(2) B1 O8 1.427(4) B5 O6 1.433(4) N9 C10 1.331(4) Si23 O24 1.610(2) B1 N9 1.695(4) B5 N25 1.695(4) N9 C14 1.319(4) Si23 C73 1.872(3) B1 C31 1.633(4) B5 C49 1.610(4) N18 C19 1.331(4) Si23 C79 1.872(3) B1 C31' 1.665(10) O6 Si7 1.614(2) N18 B21 1.708(4) O24 B211 1.433(4) O2 Si3 1.609(2) Si7 O8 1.610(2) C19 C20 1.384(4) N25 C26 1.322(4) Si3 O4 1.611(2) Si7 C55 1.880(3) B21 O22 1.438(4) N25 C30 1.322(4) Si3 C37 1.866(3) Si7 C55' 1.917(10) B21 O241 1.433(4) Si3 C43 1.874(3) Si7 C61 1.885(3) B21 C67 1.609(5) * Symmetry code: 1 -x, 1-y, 2-z. Table 3. Selected bond angles for [Ph6B2Si2O4]·L1 (4). Atom Atom Atom Angle, ° Atom Atom Atom Angle, ° Atom Atom Atom Angle, ° O2 B1 N9 103.0(2) O6 Si7 C55 104.60(17) O241 B21 C67 115.4(2) O2 B1 C31 114.5(2) O6 Si7 C55' 108.8(5) C67 B21 N18 102.0(2) O2 B1 C31' 111.0(5) O6 Si7 C61 107.0(2) B21 O22 Si23 134.0(2) O8 B1 O2 116.8(2) O6 Si7 C61' 115.8(3) O22 Si23 C73 105.51(12) O8 B1 N9 105.3(2) O8 Si7 O6 113.88(11) O22 Si23 C79 109.63(11) O8 B1 C31 111.9(2) O8 Si7 C55 113.71(19) O24 Si23 O22 113.68(11) O8 B1 C31' 111.8(5) O8 Si7 C55' 106.1(5) O24 Si23 C73 106.64(12) C31 B1 N9 103.5(2) O8 Si7 C61 104.47(15) O24 Si23 C79 111.01(13) C31' B1 N9 108.1(5) O8 Si7 C61' 103.5(3) C79 Si23 C73 110.16(13) B1 O2 Si3 138.80(18) C55 Si7 C61 113.2(2) B211 O24 Si23 143.30(19) O2 Si3 O4 113.21(11) C61' Si7 C55' 108.1(6) C26 N25 B5 122.8(2) O2 Si3 C37 111.00(12) B1 O8 Si7 147.0(2) C30 N25 B5 119.4(2) O2 Si3 C43 107.53(12) C10 N9 B1 121.0(2) C30 N25 C26 117.7(3) O4 Si3 C37 105.19(12) C14 N9 B1 121.4(2) N25 C26 C27 122.0(3) O4 Si3 C43 112.58(11) C14 N9 C10 117.5(3) N25 C30 C29 123.1(3) C37 Si3 C43 107.22(12) C17 N18 B21 118.6(2) C32' C31' B1 121.2(8) B5 O4 Si3 133.44(19) C19 N18 C17 118.7(3) C36' C31' B1 118.7(8) O4 B5 N25 102.4(2) C19 N18 B21 122.5(2) C38 C37 Si3 121.2(2) O4 B5 C49 113.2(3) N18 C19 C20 122.0(3) C42 C37 Si3 121.0(2) O6 B5 O4 115.4(2) C19 C20 C15 119.7(3) C91 O90 C93 113.9(7) O6 B5 N25 105.5(2) O22 B21 N18 105.8(2) O90 C91 C94 116.4(9) O6 B5 C49 112.8(3) O22 B21 C67 113.0(3) O90 C93 C92 107.8(7) C49 B5 N25 106.2(2) O241 B21 N18 102.7(2) C123 O120 C121 125.3(16) B5 O6 Si7 137.52(19) O241 B21 O22 115.8(2) O120 C121 C122 113.0(11) Figure 2. 1-D crystal structure of compound 4. Yellow = B, brown = Si, grey = C, blue = N, red= O. H atoms are omitted for clarity. Compound 4 is a 1-D borasiloxane/bipyridine polymer obtained as colourless crystals from the slow evaporation of diethyl ether and petroleum ether solvents mixture. At room temperature, compound 4 was soluble in organic solvents such as dichloromethane, ether, toluene and acetone. The 11B{1H} NMR spectrum of compound 4 showed a singlet at δ 20.91 ppm typical of 4-coordinate boron, while that of the starting material, compound 3 was δ 25.69 ppm typical of 3-coodinate B. Similarly, the 29Si{1H} NMR spectrum of compound 4 showed a singlet at δ -45.16 ppm and compound 3 was δ -45.00 ppm. Data obtained from a single crystal X-ray diffraction study show that compound 4 consists of an eight-membered ring structure derived from compound 3 with two B atoms coordinated to 4,4’-bipyridine (L1), resulting in the formation of a 1-D polymer as shown in Figure 2. The B-O-Si angles in compound 4 range from 133.44(19) to 147.0(2)° with an average value of 139.19(2)° and display some distortion at the O atoms as revealed in the ellipsoid plot Figure 3, and when compared with the B-O-Si angles of compound 3 (145.3(3) and 160.9(3)°) [2]. The four B-O distances in compound 4 are 1.426(4) Å (B1-O2), 1.427(4) Å (B1-O8), 1.437(4) Å (B5-O4), and 1.433(4) Å (B5-O6), and are longer than the B-O lengths for the tri-coordinated B in compound 3 (Si2B2O4), which range from (1.36-1.39 Å) [13,18,24]. However, the values reported here are similar to other B-O distances for tetrahedrally coordinated B in compounds such as N(CH2 CH2O)B (1.43(1) Å, [25]), Ph2BOCH2CH2NH2 (1.484(3) Å [26]) and Ph(OSiR2Rˊ)B{OCH2)3N} (R or Rˊ = Ph or CH3) (1.439(4) Å and 1.461(3) Å [27]) and [ButSi(OPhBO)3SiBut]·NC5H5 (1.457(18) Å and 1.469(18) Å, [24]) where the B is directly bonded to two O atoms, a phenyl group, and the N atom. The observed longer bond length at the tetrahedrally bonded B site compared to the tri-coordinated B may be linked to a reduction in B-O π-bonding component on changing from trigonal to tetrahedral coordination geometry at the B. 236 Bull et al. / European Journal of Chemistry 15 (3) (2024) 232-238 2024 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.15.3.232-238.2545 Table 4. Intramolecular hydrogen bonds for compound 4 (Å, °). Donor-H···Acceptor D-H H···A D···A ∠ D-H···A C(10)-H(10A)···O(8) 0.95 2.50 2.8480(1) 102 C(14)-H(14A)···O(2) 0.95 2.42 2.7850(1) 103 C(19)-H(19A)···O(24) 0.95 2.37 2.7630(1) 104 C(26)-H(26A)···O(4) 0.95 2.34 2.7373(1) 105 C(42)-H(42A)···O(4) 0.95 2.58 3.0297(1) 109 C(54)-H(54A)···O(6) 0.95 2.55 2.9094(1) 103 C(66)-H(66A)···O(8) 0.95 2.57 3.0164(1) 109 C(72)-H(72A)···O(22) 0.95 2.58 2.9367(1) 103 Table 5. Geometrical parameters of C–H⋅⋅⋅π contacts for the compound 4 (Å, °) *. C-H(I)···Cg(J) Symmetry H···Cg H-Perp Gamma X-H···Cg X···Cg C(105)-H(10D)···Cg(15) x, y, z 2.68 2.33 29.73 143 3.4840(1) C(13)-H(13A)···Cg(6) 1-x, -y, 2-z 2.85 2.73 16.60 135 3.5928(1) C(20)-H(20A)···Cg(5) 1-x, -y, 2-z 2.88 -2.87 4.60 130 3.5613(1) C(66'-H(66B)···Cg(3) x, y, z 2.83 2.78 10.50 119 3.3895(1) * Cg(3): N(25)-C(26)-C(27)-C(28)-C(29)-C(30); Cg(5): C(37)-C(38)-C(39)-C(40)-C(41)-C(42); Cg(6): C(43)-C(44)-C(45)-C(46)-C(47)-C(48); Cg(15): C(61')- C(62')-C(63')-C(64')-C(65')-C(66'); Cg(J) = Center of gravity of ring J; H-Perp = Perpendicular distance of H to ring plane J; Gamma = Angle between Cg-H vector and ring J normal; X-H···Cg = X-H-Cg angle (degrees); X···Cg = Distance of X to Cg (Angstrom). Figure 3. An ellipsoid view of a fragment of [Ph6B2Si2O4]·L1 (4) with some atom labelling. Yellow = B, brown = Si, grey = C, blue = N, red= O. H atoms are omitted for clarity. Figure 4. Crystal packing in [Ph6B2Si2O4]·L1(4) with four polymeric chains running parallel to the a-axis leading to formation of channels. Colour identity, pink = B, green = Si, grey = C, blue = N, red= O. H atoms and disordered solvent molecule are omitted for clarity. In addition, the four Si-O bond lengths in compound 4 range from 1.606(2) to 1.614(2) Å, and are relatively short compared to the lengths of Si-O bonds in the literature for a tetra- coordinate Si bonded to two O atoms and two carbon atoms with a mean value of 1.645 Å [18,24]. However, some Si-O bond distances similar to those reported here have been observed in the literature (1.585 to 1.634 Å) [24,27]. The shorter Si-O distances associated with compound 4 suggest an increase in the electron density in the Si-O bond, which is also consistent with the decrease in the electron density of B-O. The B-N bond lengths in compound 4 are 1.695(4) and 1.708(4) Å with an average value of 1.702(4) Å. For a simple borosiloxane such as Ph(OSiR2Rˊ)B{OCH2)3N} (R or Rˊ = Ph or CH3) [27] and [ButSi(OPhBO)3SiBut]·NC5H5 [24], the B-N distances reported were 1.639 Å and 1.655 Å, respectively. However, values of 1.556, 1.651, 1.653, 1.654, 1.676, 1.679, Bull et al. / European Journal of Chemistry 15 (3) (2024) 232-238 237 2024 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.15.3.232-238.2545 1.681, and 1.688 Å have been reported elsewhere in the literature for B-N bond length in boroxine adducts for which the B atoms were also tetra-coordinated [28-34]. The Si-C bond lengths in compound 4 range from 1.866(3) to 1.885(3) Å with an average of bond distance of 1.877(3) Å. These are as expected for single Si-C bonds [18,24,27]. The internal ring angles O2-B1-O8 and O4-B5-O6 are 116.8(2)° and 115.4(2)°, respectively, with a mean value of 116.1(2)°. These angles in compound 4 at the B centres are higher than 109.5° expected for a tetrahedral geometry, but a similar observation has been reported in the literature [24]. Similarly, the O2-Si3-O4 and O6-Si7-O8 angles are 113.21(11)° and 113.88(11)°, respectively, with a mean value of 113.6(11)°, which is also slightly higher than 109.5° expected for a tetrahedral silicon. The bond angles at the Si centre as well as the Si-C bonds are comparable to other borasiloxane compounds and simple adducts in the literature [18,24,35]. In addition to the covalent and dative bonds found in compound 4, the crystal packing (Figure 4) of the compound also shows intramolecular interactions. The parameters of the intramolecular short contacts for compound 4 are given in Table 4. Similar non-covalent interactions have been reported in cycloborasiloxane of eight-membered rings [18]. The various intermolecular and intramolecular interactions give rise to chains running parallel to the a-axis and crosslinking to form potential channels. Detailed geometric information of C-H⋅⋅⋅π stacking contacts of compound 4 is given in Table 5. 4. Conclusions In this article, Lewis acid cyclo-1,3,3,5,7,7-hexaphenyl-1,5- dibora-3,7-disiloxane (Ph6B2Si2O4) (3), has been successfully synthesized and the structure confirmed by standard analytical and spectroscopic techniques. Following this synthesis, a 4,4ˈ- bipyridine, which acted as a Lewis base, was complexed with compound 3 to give a 1D polymeric structure [Ph6B2Si2O4]·L1 (4). This novel 1D polymeric material has been characterized by standard analytical and spectroscopy methods. The polymer has channels in its packing and possesses inter molecular and intramolecular π-π interactions as well as other interactions such hydrogen bonding. Acknowledgements We gratefully acknowledge the financial support given to us by the Nigerian Government through the Petroleum Technology Development Fund (PTDF), the Tertiary Education Trust Fund (TETFUND), and the Rivers State University, Port Harcourt, Nigeria. Supporting information CCDC-2356307 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/ data_request/cif, or by e-mailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-336033. Disclosure statement Conflict of interest: The authors declare that they have no conflict of interest. Ethical approval: All ethical guidelines have been adhered to. Sample availability: Samples of the compounds are available from the author. CRediT authorship contribution statement Conceptualization: Okpara Sergeant Bull, Chioma Don-Lawson; Methodology: Okpara Sergeant Bull; Formal Analysis: Okpara Sergeant Bull; Investigation: Okpara Sergeant Bull; Resources: Chioma Don-Lawson; Data Curation: Okpara Sergeant Bull; Writing - Original Draft: Okpara Sergeant Bull; Writing -Review and Editing: Ugo Nweke-Maraizu; Visualization: Ugo Nweke- Maraizu; Funding acquisition: Chioma Don-Lawson; Supervision: Okpara Sergeant Bull; Project Administration: Ugo Nweke-Maraizu. ORCID and Email Okpara Sergeant Bull bull.okpara@ust.edu.ng https://orcid.org/0000-0002-5810-1483 Chioma Don-Lawson chioma.don-lawson@ust.edu.ng https://orcid.org/0009-0005-2593-7873 Ugo Nweke -Maraizu nwekemaraizuugo@gmail.com https://orcid.org/0009-0003-4188-0542 References [1]. Kishore, P. V. V. N.; Baskar, V. Twelve-membered B2Si4O6 borasiloxane macrocycles. J. Organomet. Chem. 2013, 743, 83–86. [2]. Brisdon, B. J.; Mahon, M. F.; Molloy, K. C.; Schofield, P. J. Synthesis and structural characterization of cycloborasiloxanes: The X-ray crystal structures of cyclo-1,3,3,5,5-pentaphenyl-1-bora-3,5-disiloxane and cyclo-1,3,3,5,7,7-hexaphenyl-1,5-dibora-3,7-disiloxane. J. Organomet. Chem. 1992, 436, 11–22. [3]. Olajire, A. A. Recent advances in the synthesis of covalent organic frameworks for CO2 capture. J. CO2 Util. 2017, 17, 137–161. [4]. Dhara, A.; Beuerle, F. Reversible assembly of a supramolecular cage linked by boron–nitrogen dative bonds. Chemistry 2015, 21, 17391– 17396. [5]. Bull, O. S. Solvothermal synthesis and characterization of a new 3D potassium Metal-Organic Framework (MOF) structure. Journal of Chemical Society of Nigeria 2020, 45 (1), 126–134 https://journals.chemsociety.org.ng/index.php/jcsn/article/view/4 34. [6]. Bull, O. S.; Bull, I.; Amadi, G. K. Global Warming and technologies for carbon capture and storage. J. Appl. Sci. Environ. Manage. 2020, 24, 1671–1686. [7]. Odu, C. O.; Obunwo, C. C.; Bull, O. S. Solvothermal synthesis and characterization of terephthalic acid-based metal-Organic Frameworks and their catalytic application in biodiesel production. Journal of Chemical Society of Nigeria 2023, 48, 474–483. [8]. Bull, O. S.; Don-Lawson, C. Facile Heck coupling synthesis and characterization of a novel tris(4-(pyridine-4-vinyl)phenyl)methyl silane tridentate core. Eur. J. Chem. 2024, 15, 71–73. [9]. Bull, O. S.; Bull, I.; Amadi, G. K.; Odu, C. O. Covalent Organic Frameworks (COFS): A Review. J. Appl. Sci. Environ. Manage. 2022, 26, 145–179. [10]. Díaz, U.; Corma, A. Ordered covalent organic frameworks, COFs and PAFs. From preparation to application. Coord. Chem. Rev. 2016, 311, 85–124. [11]. Gao, Q.; Li, X.; Ning, G.-H.; Leng, K.; Tian, B.; Liu, C.; Tang, W.; Xu, H.-S.; Loh, K. P. Highly photoluminescent two-dimensional imine-based covalent organic frameworks for chemical sensing. Chem. Commun. (Camb.) 2018, 54, 2349–2352. [12]. Foucher, D. A.; Lough, A. J.; Manners, I. Synthesis, properties, and the ring-ring transformation reactions of cyclic siloxanes incorporating skeletal boron atoms: x-ray crystal structures of the strained boracyclotrisiloxane (PhBO)(Ph2SiO)2 and the boracyclotetra siloxane (PhBO)(Ph2SiO)3. Inorg. Chem. 1992, 31, 3034–3043. [13]. O’Dowd, A. T.; Spalding, T. R.; Ferguson, G.; Gallagher, J. F.; Reed, D. Synthesis and crystal structure of the novel borosilicate cage compound [B(OSiPh2OSiPh2O)3B]. J. Chem. Soc. Chem. Commun. 1993, 1816–1817. [14]. Yoshikawa, M.; Shiba, H.; Kanezashi, M.; Wada, H.; Shimojima, A.; Tsuru, T.; Kuroda, K. Synthesis of a 12-membered cyclic siloxane possessing alkoxysilyl groups as a nanobuilding block and its use for preparation of gas permeable membranes. RSC Adv. 2017, 7, 48683– 48691. [15]. Hunt, J. R.; Doonan, C. J.; LeVangie, J. D.; Côté, A. P.; Yaghi, O. M. Reticular synthesis of covalent organic borosilicate frameworks. J. Am. Chem. Soc. 2008, 130, 11872–11873. [16]. Pascu, M.; Ruggi, A.; Scopelliti, R.; Severin, K. Synthesis of borasiloxane-based macrocycles by multicomponent condensation reactions in solution or in a ball mill. Chem. Commun. (Camb.) 2013, 49, 45–47. [17]. Liu, W.; Pink, M.; Lee, D. Conjugated polymer sensors built on π- extended borasiloxane cages. J. Am. Chem. Soc. 2009, 131, 8703–8707. [18]. Gopalakrishnan, M.; Thirumoorthy, K.; Bhuvanesh, N. S. P.; Palanisami, N. Eight membered cyclic-borasiloxanes: synthesis, structural, photophysical, steric strain and DFT calculations. RSC Adv. 2016, 6, 55698–55709. [19]. Torres-Huerta, A.; Velásquez-Hernández, M. de J.; Ramírez-Palma, L. G.; Cortés-Guzmán, F.; Martínez-Otero, D.; Hernández-Balderas, U.; Jancik, V. Synthesis of cyclic and cage borosilicates based on boronic acids and acetoxysilylalkoxides. Experimental and computational http://www.ccdc.cam.ac.uk/%20data_request/cif http://www.ccdc.cam.ac.uk/%20data_request/cif mailto:data_request@ccdc.cam.ac.uk mailto:bull.okpara@ust.edu.ng https://orcid.org/0000-0002-5810-1483 mailto:chioma.don-lawson@ust.edu.ng https://orcid.org/0009-0005-2593-7873 mailto:nwekemaraizuugo@gmail.com https://orcid.org/0009-0003-4188-0542 https://journals.chemsociety.org.ng/index.php/jcsn/article/view/434 https://journals.chemsociety.org.ng/index.php/jcsn/article/view/434 238 Bull et al. / European Journal of Chemistry 15 (3) (2024) 232-238 2024 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.15.3.232-238.2545 studies of the stability difference of six- and eight-membered rings. Inorg. Chem. 2017, 56, 10032–10043. [20]. Torres-Huerta, A.; Velásquez-Hernández, M. de J.; Martínez-Otero, D.; Höpfl, H.; Jancik, V. Structural induction via solvent variation in assemblies of triphenylboroxine and piperazine—potential application as self-assembly molecular sponge. Cryst. Growth Des. 2017, 17, 2438–2452. [21]. Beckett, M. A.; Hibbs, D. E.; Hursthouse, M. B.; Malik, K. M. A.; Owen, P.; Varma, K. S. cyclo-Boratrisiloxane and cyclo-diboratetrasiloxane derivatives and their reactions with amines: crystal and molecular structure of (p-BrC6H4BO)2(Ph2SiO)2. J. Organomet. Chem. 2000, 595, 241–247. [22]. Beckett, M. A.; Strickland, G. C.; Varma, K. S.; Hibbs, D. E.; Hursthouse, M. B.; Malik, K. M. A. Amine adducts of triarylboroxines: Synthesis and characterization of adducts of tri(2-tolyl) boroxine and crystal structures of (4-MeC6H4)3B3O3 and (4-MeC6H4) 3B3O3 · 4-picoline. J. Organomet. Chem. 1997, 535, 33–41. [23]. Bull, O. S.; Lickiss, P.; Davies, R. Silicon-Containing Cofs and Mofs for Co2 Capture, Imperial College London: Great Britain, 2018. [24]. Ferguson, G.; Lawrence, S. E.; Neville, L. A.; O’Leary, B. J.; Spalding, T. R. Synthetic and X-ray diffraction studies of borosiloxane cages [R′Si(ORBO)3SiR′] and the adducts of [ButSiO(PhB)O3SiBut] with pyridine or N,N,N′,N′-tetramethylethylenediamine. Polyhedron 2007, 26, 2482–2492. [25]. Taira, Z.; Osaki, K. The molecular structure of triethanolamine borate. Inorg. Nucl. Chem. Lett. 1971, 7, 509–512. [26]. Rettig, S. J.; Trotter, J. Crystal and molecular structure of B,B- diphenylboroxazolidine (2-aminoethyl diphenylborinate). Can. J. Chem. 1973, 51, 1288–1294. [27]. Ferguson, G.; Lough, A. J.; Sheehan, J. P.; Spalding, T. R. Structure of 2- (diphenylmethylsiloxy)-2-phenyl-1,3,2-oxazaborinane. Acta Crystallogr. C 1991, 47, 379–381. [28]. Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A. G.; Taylor, R. Tables of bond lengths determined by X-ray and neutron diffraction. Part 1. Bond lengths in organic compounds. J. Chem. Soc., Perkin Trans. 2 1987, S1-19. [29]. Clegg, W.; Scott, A. J.; Souza, F. E. S.; Marder, T. B. 1:1 Adducts of 4- picoline with methylcatecholborane and phenylcatecholborane. Acta Crystallogr. C 1999, 55, 1885–1888. [30]. Sheepwash, E.; Krampl, V.; Scopelliti, R.; Sereda, O.; Neels, A.; Severin, K. Molecular networks based on dative boron–nitrogen bonds. Angew. Chem. Int. Ed Engl. 2011, 50, 3034–3037. [31]. Cruz-Huerta, J.; Campillo-Alvarado, G.; Höpfl, H.; Rodríguez-Cuamatzi, P.; Reyes-Márquez, V.; Guerrero-Álvarez, J.; Salazar-Mendoza, D.; Farfán-García, N. Self-assembly of triphenylboroxine and the phenylboronic ester of pentaerythritol with piperazine, trans-1,4- diaminocyclohexane, and 4-aminopyridine. Eur. J. Inorg. Chem. 2016, 2016, 355–365. [32]. Saha, S.; Kottalanka, R. K.; Panda, T. K.; Harms, K.; Dehnen, S.; Nayek, H. P. Syntheses, characterization and reactivity of Lewis acid–base adducts based on B–N dative bonds. J. Organomet. Chem. 2013, 745– 746, 329–334. [33]. Icli, B.; Solari, E.; Kilbas, B.; Scopelliti, R.; Severin, K. Multicomponent assembly of macrocycles and polymers by coordination of pyridyl ligands to 1,4-bis(benzodioxaborole)benzene. Chemistry 2012, 18, 14867–14874. [34]. Viswanathan, T.; Gopalakrishnan, M.; Thirumoorthy, K.; Prakash, M.; Palanisami, N. Enhancement of second-order nonlinear optical properties of centrosymmetric ferrocenyl borasiloxane by a broken- symmetry approach. J. Phys. Chem. C Nanomater. Interfaces 2021, 125, 8732–8740. [35]. Foucher, D. A.; Lough, A. J.; Manners, I. A highly strained heterocyclosiloxane: synthesis and X-ray crystal structure of pentaphenylboracyclotrisiloxane BSi2O3Ph5. J. Organomet. Chem. 1991, 414, C1–C4. Copyright © 2024 by Authors. This work is published and licensed by Atlanta Publishing House LLC, Atlanta, GA, USA. The full terms of this license are available at https://www.eurjchem.com/index.php/eurjchem/terms and incorporate the Creative Commons Attribution-Non Commercial (CC BY NC) (International, v4.0) License (http://creativecommons.org/licenses/by-nc/4.0). By accessing the work, you hereby accept the Terms. This is an open access article distributed under the terms and conditions of the CC BY NC License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited without any further permission from Atlanta Publishing House LLC (European Journal of Chemistry). No use, distribution, or reproduction is permitted which does not comply with these terms. Permissions for commercial use of this work beyond the scope of the License (https://www.eurjchem.com/index.php/eurjchem/terms) are administered by Atlanta Publishing House LLC (European Journal of Chemistry). https://www.eurjchem.com/index.php/eurjchem/terms http://creativecommons.org/licenses/by-nc/4.0 https://www.eurjchem.com/index.php/eurjchem/terms 1. Introduction 2. Experimental 2.1. Chemicals and reagents 2.2. Instrumentation 2.3. Synthesis 2.3.1. Preparation of Ph6B2Si2O4 (3) 2.3.2. Preparation of [Ph6B2Si2O4] L1 (4) 3. Results and discussion 4. Conclusions Acknowledgements Supporting information Disclosure statement CRediT authorship contribution statement ORCID and Email References PrintField10: PrintField11: PrintField12: PrintField13: PrintField14: PrintField15: PrintField16: PrintField20: PrintField21: PrintField22: PrintField23: PrintField24: PrintField25: PrintField26: