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Article

Synthesis and Structures of Lead(II) Complexes with Substituted Derivatives of the Closo-Decaborate Anion with a Pendant N3 Group

by
Evgenii Yu. Matveev
1,2,
Olga S. Dontsova
1,2,
Varvara V. Avdeeva
2,*,
Alexey S. Kubasov
2,
Andrey P. Zhdanov
2,
Svetlana E. Nikiforova
2,
Lyudmila V. Goeva
2,
Konstantin Yu. Zhizhin
1,2,
Elena A. Malinina
2 and
Nikolay T. Kuznetsov
2
1
Institute of Fine Chemical Technologies Named after M. V. Lomonosov, MIREA—Russian Technological University, Vernadskogo pr. 86, Moscow 119571, Russia
2
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow 119991, Russia
*
Author to whom correspondence should be addressed.
Molecules 2023, 28(24), 8073; https://doi.org/10.3390/molecules28248073
Submission received: 15 November 2023 / Revised: 5 December 2023 / Accepted: 11 December 2023 / Published: 13 December 2023
(This article belongs to the Section Inorganic Chemistry)
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Versions Notes

Abstract

:
In this work, we studied lead(II) and cobalt(II) complexation of derivatives [2-B10H9O(CH2)2O(CH2)2N3]2− and [2-B10H9O(CH2)5N3]2− of the closo-decaborate anion containing pendant azido groups in the presence of 1,10-phenanthroline and 2,2′-bipyridyl. Mononuclear [PbL2{An}] and binuclear [Pb2L4(NO3)2{An}] lead complexes (where {An} is the N3-substituted boron cluster) were isolated and studied by IR spectroscopy and elemental analysis. The mononuclear lead(II) complex [Pb(phen)2[B10H9O(CH2)2O(CH2)2N3] and the binuclear lead(II) complex [Pb2(phen)4(NO3)2[B10H9O(CH2)5)N3] were determined by single-crystal X-ray diffraction. In complex [Pb2(phen)4(NO3)2[B10H9O(CH2)5)N3], the boron cluster is coordinated by the metal atom only via the 3c2e MHB bonds. In complex [Pb(phen)2[B10H9O(CH2)2O(CH2)2N3], the coordination environment of the metal includes BH groups of the boron cluster and the oxygen atom of the exo-polyhedral substituent. When the reaction was performed in a CH3CN/water mixture, the binuclear lead(II) complex [(Pb(bipy)NO3)(Pb(bipy)2NO3)(B10H9O(CH2)2O(CH2)2N3)]·CH3CN·H2O was isolated, where the boron cluster acts as a bridging ligand between lead atoms coordinated by the boron cage via the O atoms of the substituent and/or the BH groups. In the course of cobalt(II) complexation, the starting compound (Ph4P)2[B10H9O(CH2)5N3] was isolated and its structure was also determined by X-ray diffraction. Although a number of lead(II) complexes with coordinated N3 are known from the literature, no complexes with the boron cluster coordinated by the pendant N3 group involved in the metal coordination have been isolated.

Graphical Abstract

1. Introduction

Boron cluster anions [BnHn]2− (n = 6–12) attract attention as completely inorganic clusters with high resistance to elevated temperatures and oxidizing agents, but at the same time are quite easily subjected to direct functionalization due to the substitution of terminal hydrogen atoms with various functional groups [1,2,3,4,5]. The derivatives obtained can be used in further modification reactions, for example, due to the presence of thiol [6,7,8,9], nitrile [10,11,12], hydroxyl [13,14,15], and other groups. Compounds based on the most well-known closo-borate anions, [B10H10]2− and [B12H12]2−, are actively studied and used in various fields of science and technology, for example, in the creation of energy storage systems, the synthesis of composite materials, materials for electronics, etc. [16,17,18,19,20]. Preparations based on boron cluster anions and carboranes are used for diagnostics and neutron capture therapy of malignant tumors (10B NCT) [21,22,23] and have antimicrobial [24,25] and antiviral [26,27,28] effects. In this regard, the search for new methods for the functionalization of [B10H10]2− and [B12H12]2− anions is an urgent task.
Derivatives of higher boron anions [BnHn]2− (n = 10, 12) with cyclic substituents of the oxonium type are easily modified, affording closo-borates with pendant functional groups [29,30,31,32,33,34,35,36,37]. These reactions proceed under the action of a wide range of nucleophilic reagents and are accompanied by the opening of a cyclic substituent. Functional groups attached through the alkoxy spacer chain and isolated in this way can enter into further functionalization reactions, including fragments of biologically active molecules [32,38,39]. Boron cluster anion derivatives containing a pendant azido group are of particular interest as objects for direct application in click chemistry [40,41,42,43].
Anions [BnHn]2− (n = 10, 12) and their derivatives are currently of considerable interest in the synthesis of complex compounds. To date, quite a lot of examples of their application both as counterions [44,45,46] and as polydentate and polytope ligands [47,48] have been described. Closo-borates with pendant functional groups have great potential in complexation due to the presence of several coordination centers: a Pearson soft boron cluster, an alkoxy spacer group, and an introduced pendant fragment. Varying the structure of the spacer (both by length and the presence of donor atoms of various types) and the pendant fragment opens up great prospects in the synthesis of metal coordination compounds with different Pearson hardness/softness levels, as well as complexes with the desired structures and properties. For example, the lead(II) complexation with hydroxy-closo-decaborates with different types of binding of the OH group to the boron cluster leads to mono-, binuclear, and polymeric complexes [49]. Research in this area is of interest both from the point of view of fundamental science and from the point of view of practice, for example, for the synthesis of functional boron-containing materials [50,51].
It is known that the azide ion is able to be coordinated by lead(II) in various ways; in particular, it can act as a tridentate (μ1,1,1-N3 or μ1,1,3-N3) and a bidentate bridging ligand (μ1,1-N3 or μ1,3-N3) [52]. The obtained derivatives can be used in the synthesis of organometallic coordination polymers; therefore, studies in this field of lead(II) coordination chemistry are topical.
The aim of this work is to synthesize and study the closo-decaborate anion derivatives containing pendant azido groups in lead(II) and cobalt(II) complexation in the presence of azaheterocyclic ligands, namely 1,10-phenanthroline and 2,2′-bipyridyl.

2. Results and Discussion

Derivatives of the closo-decaborate anion containing a pendant N3 group [2-B10H9RN3]2− (where R = O(CH2)2O(CH2)2) (1) or O(CH2)5 (2)) were obtained by multistage synthesis starting from the [B10H10]2− anion (Scheme 1), as reported in [53].
Compounds 1 and 2 were synthesized according to the known procedure reported in [53]. The introduction of an exo-polyhedral substituent and its subsequent opening with the formation of closo-decaborates containing pendant azido groups were monitored using 11B and 11B{1H} NMR spectroscopy. For example, in the 11B{1H} NMR spectrum of the closo-decaborate anion, there were only two signals with an integral intensity ratio of 1:4 from two apical and eight equatorial boron atoms, respectively. In the 11B{1H} spectrum of the product of the reaction with 1,4-dioxane and salt K[B10H9O(CH2)4O], there was one signal at 7.7 ppm from the ipso-boron atom, two signals at 0.8 and 6.4 ppm assigned to two chemically non-equivalent apical vertices, two signals at −21.5 and −23.4 ppm corresponding to two pairs of equatorial boron atoms adjacent to the ipso position, and one signal at −29.9 ppm assigned to three boron atoms opposite the substituted position. Only one signal at 7.7 ppm did not split into a doublet in the 11B NMR spectrum. This spectral pattern makes it possible to unambiguously determine the type of compounds obtained. The 11B{1H} NMR spectrum of the product of the reaction of the 1,4-dioxane derivative with the [B10H10]2− anion with sodium azide retained the general form characteristic of closo-decaborates with a substituent in the equatorial belt; however, it exhibited a significant rearrangement of signals from boron atoms when compared with the spectrum of the initial derivative of the closo-decaborate anion. In particular, the signal from the ipso boron atom at 7.7 ppm shifted towards the strong field up to −1.9 ppm due to a change in the type of the substituent atom from oxonium to alkoxy and a decrease in the polarity of the B–O bond. The signals from two nonequivalent apical vertices of the polyhedron approached each other in the spectrum of the reaction product and changed their positions from −0.8 and −6.4 ppm to −3.8 and −4.8 ppm, respectively. These characteristic changes in the spectra of the products were associated with changes in the valence and charge of the oxonium oxygen atom. The structure of the exo-polyhedral substituent was determined by 1H NMR and IR spectroscopies.
The obtained compounds 1 and 2 can be considered organic azides with a framework substituent in the form of a boron cluster. It should also be noted that the obtained compounds are very stable in light and air, and in solutions up to a temperature of 100 °C they do not undergo transformations in the azido group. In terms of thermal and kinetic stability, they can be compared with aryl and adamantylazide, which are known coordination compounds with transition metals. In these complexes, the organoazide group shows various coordination possibilities. The organoazide can be monodentate coordinated; this type is characteristic of copper, silver, cobalt, and palladium complexes [54,55,56,57,58]. μ1,1-N3 bridging coordination is known for a heterometallic zirconium–iridium complex [59]. η2-Coordination is observed in the case of some nickel complexes [60]. Quite a large group is formed by complexes with μ1,1,1-N3 coordination of the azido moiety; this type of binding is characteristic of tantalum, vanadium, tungsten, and titanium ions [61,62,63,64,65,66]. Often, in complexes of this type, the azide moiety is spontaneously or by thermal effect converted to an imido species by extrusion of the N2 molecule.
Substituted derivatives with a pendant N3 group were subsequently used as ligands in lead(II) complexation reactions in the presence of organic ligands phen and bipy. Solid lead(II) nitrate was added to a solution of salt (Ph4P)2[B10H9R] in acetonitrile (R = O(CH2)2O(CH2)2) or O(CH2)5). Organic ligands bipy and phen were added to the reaction solution (in a metal-to-ligand ratio of 1:2) to stabilize the lead(II) complexes formed. The complexation was carried out according to Scheme 2.
The final compounds are mononuclear lead(II) complexes [PbL2[B10H9O(CH2)2O(CH2)2N3] (L = bipy (3), phen (4)) and binuclear lead(II) complexes [Pb2L4(NO3)2[B10H9O(CH2)5)N3] (L = bipy (5), phen (6)). The IR spectra of the obtained compounds 3–6 contain a broad, intense band of stretching vibrations ν(BH) near 2400 cm−1 assigned to uncoordinated BH bonds and a band ν(BH)MHB, which is observed as a shoulder in the region of 2300–2200 cm−1. The presence of bands in the region 2300–2200 cm−1 indicates the coordination of the boron cage via the MHB bond. A broad band of the stretching vibrations ν(NO) is observed in the IR spectra of complexes 5 and 6. The spectra of all compounds contain bands in the region 1700–600 cm−1, which indicate the presence of coordinated bipy and phen molecules.
We succeeded in isolating single crystals of complexes 4 and 6·3CH3CN, which were suitable for further X-ray diffraction studies.
The crystallographically independent part of the triclinic unit cell (P-1) of complex 4 includes the binuclear complex [Pb(phen)2[µ-B10H9O(C2H4)O(C2H4)N3]]2 (Figure 1). Anions [B10H9O(C2H4)O(C2H4)N3]2− act as bridging ligands; each anion is coordinated to one lead atom through the oxygen atom O1(O3) and the B6B9 edge (B16B19) and to the second metal atom along the B9B10 edge (B19B20), forming two pairs of three-center two-electron Pb–HBBH bonds. Thus, the coordination environment of each lead atom includes four nitrogen atoms from two phenanthroline molecules, an oxygen atom of the exo-polyhedral substituent, and two edges, B6B9 and B9B10, from two anions (Figure 1). The Pb–O bond lengths are 2.443(7) and 2.562(7) Å, the Pb–B bond lengths fall in the range 3.358(12)–3.593(11) Å, and the Pb–H bond lengths are 3.044(2)–3.7752(14) Å (Table 1). The exo-polyhedral substituent of one of the anions is disordered with a population of 0.65:0.35, with large thermal vibrations of the azide group.
Almost all phenanthroline ligands are slightly distorted from a perfectly flat state (RSMD ranges from 0.038 to 0.066 Å). The angles between the PbNN and phen planes lie in the range of 153.9°–167.3°, which is associated with the formation of intra- and intermolecular π–π stacking interactions between the ligands. Molecules connected in this way form 1D polymer chains (Figure 2), which are interconnected through the CH…HB contacts.
The crystallographically independent part of the triclinic unit cell (P-1) of complex 6·3CH3CN contains the binuclear complex [(Pb2(Phen)4(NO3))2[µ-B10H9O(CH2)5N3]], in which the [B10H9O(CH2)5N3]2− anion acts as a bridging ligand, and there are three solvate molecules of acetonitrile (Figure 3). The coordination environment of each lead atom includes two phen molecules, one nitrate ion, and one B5B8B9 and B3B6B7 face forming the environment of the Pb1 and Pb2 atoms, respectively. The Pb–B bond lengths in complex 6·3CH3CN are significantly shorter than those for complex 4, on average by 0.23 Å (Table 2). The average value of Pb–H contacts in complex 6 is shorter by 0.5 Å. The exo-polyhedral substituent in this case does not participate in coordination and is bonded to neighboring complexes only through CH…O and CH…N contacts. The angles between the PbNN and phen planes lie in the range of 163.8°–178.4°, which is also associated with the formation of π–π stacking interactions between phenanthroline ligands. Solvent molecules are located in channels of square cross-sections parallel to axis a (Figure 4).
It is interesting that when we used the water/acetonitrile mixture to perform the lead complexation reaction (instead of CH3CN, used to prepare complexes 3–6), we succeeded in isolating complex 7 for starting compound 1 (see Scheme 3).
In other cases, no boron-containing complexes were isolated; for example, crystals [Pb(bipy)2(NO3)2]2 [67] (as determined by X-ray single-crystal diffraction) were isolated.
The IR spectrum of complex 7 is similar to related complex 4; no significant changes could be found. However, the elemental analysis data indicated a 3:2 ratio of M:L instead of the 4:2 ratio found for complexes 3–6.
The crystallographically independent part of the monoclinic unit cell of complex 7 0.5CH3CN·0.125H2O contains the binuclear lead(II) complex [(Pb(bipy)NO3)(Pb(bipy)2NO3)(B10H9O(CH2)2O(CH2)2N3)] (Figure 5). The terminal fragment (CH2)2N3 of the exo-polyhedral substituent is disordered into four positions with occupancies 0.3:0.3:0.2:0.2. The coordination environment of the Pb1 atom includes the B7B8 edge of the boron cage, two bipy molecules, and one nitrate anion. The Pb1–B bond lengths are 3.302(15) Å and 3.317(15) Å, whereas the Pb1–H bond lengths are 2.81(9) Å and 3.06(8) Å. The coordination environment of the Pb2 atom includes two oxygen atoms of the exo-polyhedral substituent (the length of the Pb2–O2 bond is significantly extended as compared to that of Pb2–O2; the Pb2–O1 bond length is 2.530(10) Å and the Pb2–O2 bond length is 2.882(13) Å).
Complex 7, similar to compound 4, forms 1D polymer units due to π–π stacking interactions between bipy molecules of neighboring complexes. The units are interconnected through CH…HB contacts (Figure 6), forming channels parallel to axis c, which are filled with disordered solvent molecules.
In spite of the ability of lead(II) to form compounds with the N3 group coordinated by different methods [52], it seems that the softer boron cluster is preferable to form the coordination environment of the metal atom as compared to the azido group. We concluded that the N3 group is too hard to be coordinated by lead(II) in the presence of BH groups.
Therefore, we tried to study cobalt(II) complexation because this metal is harder compared to lead(II). A number of cobalt(II) complexes with organoazides coordinated are known [57]; therefore, the formation of cobalt(II) complexes with boron clusters coordinated via the azide functional group could be expected. The experiments performed for compound 2 in the case of using Co(II) as a complexing agent revealed that the closo-decaborates with a pendant N3 functional group act as extremely weakly coordinating ligands in the absence of chelating ligands. In an attempt to obtain a Co(II) complex, when the closo-decaborate anion containing an azide pendent group was allowed to react with CoCl2 in the CH3CN/H2O system, the initial derivative of the closo-decaborate anion (compound 2) was formed as a solid phase, the structure of which was determined by X-ray diffraction (Figure 7). According to the X-ray diffraction data, the structure of compound 2 consists of two Ph4P+ cations and the [2-B10H9O(CH2)5N3]2− anion (Figure 7). The IR and 11B NMR data correlate with those reported [53].
At the same time, when organic ligands L (bipy or phen) were used as additional ligands in the same reaction and the reaction was performed in CH3CN, heteroleptic cobalt(II) complexes [Co(bipy)2Cl2] or [Co(phen)2Cl2] were isolated, according to the single-crystal diffraction data [57,68]. In both cases, the starting compound (compound 2) remained unreacted. It could be concluded that cobalt(II) seems to be too hard to form compounds with coordinated boron clusters and their derivatives. The reactions proceeded according to Scheme 4.

3. Experimental Section

3.1. Materials

Lead nitrate (99%), anhydrous cobalt chloride (98%), 2,2′-bipyridyl (bipy) (99%,), phenanthroline (phen) (99%), acetonitrile (for HPLC), tetrahydropyran (99%), 1,4-dioxane (99%), potassium hydroxide (95%), sodium azide (95%), and tetraphenylphosphonium chloride (99.9%) were purchased from Sigma-Aldrich (St. Louis, MO, USA) and used without additional purification.

3.2. Syntheses

3.2.1. Synthesis of Compounds 1 and 2

Tetraphenylphosphonium 2-[2-(2-azidoetoxy)etoxy)]nonahydro-closo-decaborate (2-), (Ph4P)2[B10H9O(CH2)2O(CH2)2N3] (1) and tetraphenylphosphonium 2-[5-azidopentoxy]nonahydro-closo-decaborate (2-) (Ph4P)2[B10H9O(CH2)5N3] (2) were synthesized according to the previously reported method [53].
(Ph4P)2[B10H9O(CH2)2O(CH2)2N3] (1)
11B{H} NMR (CD3CN, ppm): −1.6 (s, 1B, B(2)), −3.1 (s, 1B, B(10)), −5.6 (s, 1B, B(1)), −23.7 (s, 4B, B(3,5,6,9)), −29.2 (s, 2B, B(7,8)), −34.1 (s, 1B, B(4)). 1H NMR (CD3CN, ppm): 7.95, 7.79, 7.71 (m, 40H, Ph4P+), 3.71 (t, 2H, OCH2CH2N3, J = 6.2 Hz), 3.25 (t, 2H, OCH2CH2OCH2, J = 5.3 Hz), 3.16 (t, 2H, OCH2CH2OCH2, J = 5.3 Hz), 3.08 (t, 2H, OCH2CH2N3, J = 6.2 Hz), 2.5…−0.5 (m, 9H, B-H). IR (selected bands, ν, cm−1): 2450 (ν(B–H)); 2108 (ν(N–N)).
(Ph4P)2[B10H9O(CH2)5N3] (2)
11B{H} NMR (CD3CN, ppm): −1.7 (s, 1B, B(2)), −2.7 (s, 1B, B(10)), −5.2 (s, 1B, B(1)), −23.8 (s, 4B, B(3,5,6,9)), −28.9 (s, 2B, B(7,8)), −33.6 (s, 1B, B(4)). 1H NMR (CD3CN, ppm): 7.96, 7.79, 7.70 (m, 40H, Ph4P+), 3.42 (t, 2H, OCH2CH2, J = 6.2 Hz), 3.05 (t, 2H, CH2CH2N3, J = 6.0 Hz), 1.86 (m, 2H, OCH2CH2CH2), 1.79 (m, 2H, CH2CH2N3), 1.32 (m, 2H, OCH2CH2CH2), 2.0…−0.5 (m, 9H, B-H). IR (selected bands, ν, cm−1): 2458 (ν(B–H)); 2112 (ν(N–N)).

3.2.2. Synthesis of Compounds 3–7

Pb(L)2[B10H9O(C2H4)O(C2H4)N3] (3:L = bipy, 4:L = phen) and Pb2(L)4(NO3)2[B10H9O(CH2)5N3] (5:L = bipy, 6:L = phen).
Solid Pb(NO3)2 (0.2 mmol) was added to a solution of (Ph4P)2[An] (where [An]2− = [B10H9O(CH2)2O(CH2)2N3]2− (1) or [B10H9O(CH2)5N3]2− (2)) (0.2 mmol) in acetonitrile (10 mL) and stirred for an hour. The unreacted Pb(NO3)2 was filtered off. A solution of ligand (phen, bipy) (0.4 mmol) in acetonitrile (10 mL) was added to the resulting yellow solution; the resulting mixture acquired a more saturated color. The formation of yellow crystals was observed after 20–25 min. Yield, 60–70%. Single crystals 4 and 6·3CH3CN suitable for X-ray diffraction study were taken directly from the reaction solutions.
(3) Anal. calcd. for [Pb(bipy)2[B10H9O(CH2)2O(CH2)2N3], %: C, 37.6; H, 4.3; N, 12.8; B, 14.1; Pb, 27.0. Found for PbC24H33N7O2B10, %: C, 37.1; H, 4.2; N, 12.5; B, 14.2; Pb, 26.8. IR (ν, cm−1): ν(BH) 2464; ν(BH)BHB 2359; ν(NN) 2093; ν(CH)bipy 3068; ν(CN, CC)bipy 1601, 1573, π(CH) 762.
(4) Anal. calcd. for [Pb(phen)2[B10H9O(C2H4)O(C2H4)N3], %: C, 41.3; H, 4.1; N, 12.0; B, 13.3; Pb, 25.4. Found for PbC28H33N7O2B10, %: C, 41.7; H, 4.3; N, 12.1; B, 14.2; Pb, 25.3. IR (ν, cm−1): ν(BH) 2452; ν(BH)BHB 2346; ν(N-N) 2095; ν(CH)phen 3065; ν(CN, CC)phen 1618, 1593, 1579; π(CH) 848, 720.
(5) Anal. calcd. for [Pb2(bipy)4(NO3)2[B10H9O(CH2)5N3], %: C, 38.4; H, 3.7; N, 12.9; B, 7.7; Pb, 29.5. Found for Pb2C45H51N13O7B10, %: C, 38.8; H, 3.4; N, 12.8; B, 7.8; Pb, 29.2. IR (ν, cm−1): ν(BH) 2452; ν(BH)BHB 2346; ν(NN) 2095; ν(NO)NO3 1500–1300; ν(CH)bipy 3069; 1605, 1572; π(CH) 760.
(6) Anal. calcd. for [Pb2(phen)4(NO3)2[B10H9O(CH2)5N3], %: C, 42.3; H, 3.4; N, 12.1; B, 7.2; Pb, 27.6. Found for Pb2C53H51N13O7B10, %: C, 42.3; H, 3.4; N, 12.1; B, 7.1; Pb, 27.7. IR (ν, cm−1): ν(BH) 2452; ν(BH)BHB 2346; ν(NN) 2094; ν(NO)NO3 1500–1300; ν(CN, CC)phen 1620, 1595, 1578; π(CH) 851, 723.
[(Pb(bipy)NO3)(Pb(bipy)2NO3)(B10H9O(CH2)2O(CH2)2N3)] (7)
Pb(NO3)2 (0.2 mmol) was dissolved in water (5 mL) and the obtained solution was added to a solution of (Ph4P)2[An] (2) (0.2 mmol) in acetonitrile (10 mL). A solution of ligand (phen) (0.4 mmol) in acetonitrile (10 mL) was added to the resulting solution. The reaction mixtures of pale-yellow color were kept in air. The formation of yellow crystals was observed within 24 h. Yield, 57%. Single crystal 7·CH3CN·H2O suitable for X-ray diffraction study was taken directly from the reaction solution.
(7) Anal. calcd. for [(Pb(bipy)NO3)(Pb(bipy)2NO3)(B10H9O(CH2)2O(CH2)2N3)], %: C, 34.9; H, 3.5; N, 6.0; B, 9.2; Pb, 35.4. Found for Pb2C34H41N5O8B10, %: C, 34.7; H, 3.4; N, 6.2; B, 9.0; Pb, 35.2. IR (ν, cm−1): ν(BH) 2465; ν(BH)BHB 2353; ν(NN) 2094; ν(CH)bipy 3067; ν(CN, CC)bipy 1610, 1573, π(CH) 760.

3.2.3. Cobalt(II) Complexation Using Compound 2

CoCl2 (0.2 mmol) was dissolved in water (5 mL) and the obtained solution was added to a solution of (Ph4P)2[An] (2) (0.2 mmol) in acetonitrile (10 mL). The formation of gray crystal 2 was observed within 48 h. Yield, 78%. Single crystal 2 suitable for X-ray diffraction study was taken directly from the reaction solution. Data of physicochemical methods of analysis (NMR, IR) correlate with those indicated above for compound 2.
CoCl2 (0.2 mmol) was dissolved in acetonitrile (5 mL) and the obtained blue solution was added to a solution of (Ph4P)2[An] (2) (0.2 mmol) in acetonitrile (10 mL). A solution of ligand (bipy or phen) (0.4 mmol) in acetonitrile (10 mL) was added to the resulting solution. The reaction mixtures were kept in air. Crystals [Co(bipy)2Cl2] and [Co(phen)2Cl2], respectively, were isolated from the reaction mixture after 48 h. According to the single-crystal diffraction data, the cell parameters of crystals correspond to known compounds [68,69]. Yield, 68% for [Co(bipy)2Cl2] and 72% for [Co(phen)2Cl2]. Compound 2 remained unreacted.

3.3. Methods

Elemental analysis of compounds 3–6 for carbon, hydrogen, and nitrogen was performed using a Carlo ErbaCHNS-3 FA 1108 automated elemental analyzer. Boron and metal content was determined on an iCAP 6300 Duo ICP emission spectrometer with inductively coupled plasma. Before the measurements, samples were dried in a vacuum to constant weight.
IR spectra of compounds were recorded on an Infralum FT-02 IR Fourier spectrometer (Lumex) in the range 4000–600 cm−1 at a resolution of 1 cm−1. Specimens were prepared as suspensions in Nujol mull (Aldrich), and NaCl glasses were used.
1H and 11B NMR spectra of CD3CN solutions of compounds 1 and 2 under study were recorded on a Bruker Avance II-300 spectrometer operating at a frequency of 300.3 and 96.32 MHz, respectively, using internal deuterium lock. Tetramethylsilane and boron trifluoride etherate were used as external references.
Single-crystal X-ray diffraction data for complexes 2, 4, 6·3CH3CN, and 7·0.5CH3CN·0.125H2O were collected on a three-circle Bruker D8 Venture diffractometer (T = 100 K, graphite monochromator, ω and φ scanning mode). The data were indexed and integrated using the SAINT program [70] and then scaled and corrected for absorption using the SADABS program [71]. For details, see Table S1 (Supplementary Materials).
The structure of 4 was determined by the intrinsic phasing method, and the structures of 2, 6, and 7 were solved by the charge flipping method implemented in Olex2 and refined by full-matrix least squares technique on F2 with anisotropic displacement parameters for non-hydrogen atoms. The hydrogen atoms were placed in calculated positions and refined within a riding model with fixed isotropic displacement parameters [Uiso(H) = 1.5Ueq(O), 1.5Ueq(C) for the CH3 groups and 1.2Ueq(C) for the other groups]. All calculations were carried out using the SHELXL program [72] and OLEX2 program package [73]. Errors in crystals 4 and 6 are probably due to the presence of a small twin component.
Crystallographic data for all investigated compounds have been deposited with the Cambridge Crystallographic Data Center, CCDC nos. 2307854–2307857. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: +44-1223-336033; e-mail: [email protected] or www.ccdc.cam.ac.uk; accessed on 12 December 2023).

4. Conclusions

Here, we studied lead(II) and cobalt(II) complexations of derivatives of the closo-decaborate anions [2-B10H9O(CH2)2O(CH2)2N3]2− and [2-B10H9O(CH2)5N3]2− containing pendant azido groups in the presence of 1,10-phenanthroline and 2,2′-bipyridyl. It was found that in acetonitrile, both derivatives form mononuclear lead(II) complexes [PbL2{An}] or binuclear lead(II) complexes [Pb2L4(NO3)2{An}] with the N3-substituted boron cluster coordinated via the BH groups or the BH group and the O atom of the substitute. In the CH3CN/water system, we succeeded in isolating complex [Pb2L3(NO3)2{An}] (An = [2-B10H9O(CH2)5N3]2−), where the N3-substituted boron cluster is coordinated by lead(II) via the BH groups and the O atom of the substitute. Complexes with a pendant N3 group involved in the metal coordination were not isolated. In the course of cobalt(II) complexation, starting compound (Ph4P)2[B10H9O(CH2)5N3] remained unreacted.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/molecules28248073/s1, Table S1: Crystal data and structure refinement for compounds 2–7, Crystallographic data files for compounds 2–7.

Author Contributions

Investigation, E.Y.M., O.S.D. and V.V.A.; Methodology, V.V.A.; Data curation and Formal analysis, L.V.G. and S.E.N.; Validation, A.S.K.; Visualization, A.S.K. and A.P.Z.; Writing—original draft preparation, E.Y.M. and O.S.D.; Writing—review and editing, V.V.A.; Conceptualization, E.A.M. and K.Y.Z.; Supervision, N.T.K. All authors have read and agreed to the published version of the manuscript.

Funding

The work was supported by the Ministry of Science and Higher Education of the Russian Federation, agreement no. 075-15-2020-779 (Russia).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article and Supplementary Materials.

Acknowledgments

X-ray diffraction studies were carried out within the framework of the State Assignment of the Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences in the field of fundamental scientific research.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare that they have no conflicts of interest.

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Scheme 1. Synthesis of substituted derivatives [2-B10H9RN3]2−, where R = O(CH2)2O(CH2)2) (1) or O(CH2)5 (2).
Scheme 1. Synthesis of substituted derivatives [2-B10H9RN3]2−, where R = O(CH2)2O(CH2)2) (1) or O(CH2)5 (2).
Molecules 28 08073 sch001
Molecules 28 08073 sch002
Scheme 2. Synthesis of lead(II) complexes 3–6 with substituted derivatives [2-B10H9R]2− in acetonitrile.
Scheme 2. Synthesis of lead(II) complexes 3–6 with substituted derivatives [2-B10H9R]2− in acetonitrile.
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Figure 1. Structure of complex 4 (left) and coordination environment of lead atoms in the complex (right).
Figure 1. Structure of complex 4 (left) and coordination environment of lead atoms in the complex (right).
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Figure 2. Packing diagram of complex 4.
Figure 2. Packing diagram of complex 4.
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Figure 3. Structure of complex 6·3CH3CN.
Figure 3. Structure of complex 6·3CH3CN.
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Figure 4. Packing diagram of complex 6·3CH3CN.
Figure 4. Packing diagram of complex 6·3CH3CN.
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Scheme 3. Synthesis of lead(II) complex 7 with substituted derivative [2-B10H9R]2− (R = O(CH2)2O(CH2)2)N3) in acetonitrile.
Scheme 3. Synthesis of lead(II) complex 7 with substituted derivative [2-B10H9R]2− (R = O(CH2)2O(CH2)2)N3) in acetonitrile.
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Figure 5. Structure of complex [(Pb(bipy)NO3)(Pb(bipy)2NO3)(B10H9O(CH2)2O(CH2)2N3)]·CH3CN·H2O (7·0.5CH3CN·0.125H2O). Thermal ellipsoids are shown with 30% probability level.
Figure 5. Structure of complex [(Pb(bipy)NO3)(Pb(bipy)2NO3)(B10H9O(CH2)2O(CH2)2N3)]·CH3CN·H2O (7·0.5CH3CN·0.125H2O). Thermal ellipsoids are shown with 30% probability level.
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Figure 6. Packing diagram of complex 7·0.5CH3CN·0.125H2O.
Figure 6. Packing diagram of complex 7·0.5CH3CN·0.125H2O.
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Figure 7. Structure of compound 2.
Figure 7. Structure of compound 2.
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Scheme 4. Cobalt(II) complexation reaction performed for compound 2.
Scheme 4. Cobalt(II) complexation reaction performed for compound 2.
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Table 1. Selected bond lengths in the structure of 1.
Table 1. Selected bond lengths in the structure of 1.
BondLength, ÅBondLength, Å
Pb–O12.443(7)Pb2–O32.562(7)
Pb–N42.636(8)Pb2–N112.616(8)
Pb–N52.571(9)Pb2–N122.648(8)
Pb–N62.637(8)Pb2–N132.662(8)
Pb–N72.572(8)Pb2–N142.550(8)
Pb–B63.593(11)Pb2–B163.524(13)
Pb–H63.7752(14)Pb2–H163.6561(14)
Pb–B93.359(10)Pb2–B193.358(12)
Pb–H93.2227(19)Pb2–H193.2198(19)
Pb–B193.437(12)Pb2–B93.567(11)
Pb–H192.9610(19)Pb2–H93.044(2)
Pb–B203.463(13)Pb2–B103.566(11)
Pb–H203.4576(14)Pb2–H103.5091(14)
Table 2. Selected bond lengths in the structure of complex 6·3CH3CN.
Table 2. Selected bond lengths in the structure of complex 6·3CH3CN.
BondLength, ÅBondLength, Å
Pb1-O22.631(6)Pb2-O52.683(6)
Pb1-O42.791(6)Pb2-O62.695(6)
Pb1-N52.590(7)Pb2-N102.608(7)
Pb1-N62.549(7)Pb2-N112.624(7)
Pb1-N72.598(7)Pb2-N122.520(7)
Pb1-N82.624(7)Pb2-N132.610(7)
Pb1-B53.280(11)Pb2-B33.338(11)
Pb1-H52.8317(11)Pb2-H32.9056(8)
Pb1-B83.197(10)Pb2-B63.192(10)
Pb1-H82.8195(10)Pb2-H62.7792(10)
Pb1-B93.224(10)Pb2-B73.268(10)
Pb1-H92.8843(12)Pb2-H72.9327(12)
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Matveev, E.Y.; Dontsova, O.S.; Avdeeva, V.V.; Kubasov, A.S.; Zhdanov, A.P.; Nikiforova, S.E.; Goeva, L.V.; Zhizhin, K.Y.; Malinina, E.A.; Kuznetsov, N.T. Synthesis and Structures of Lead(II) Complexes with Substituted Derivatives of the Closo-Decaborate Anion with a Pendant N3 Group. Molecules 2023, 28, 8073. https://doi.org/10.3390/molecules28248073

AMA Style

Matveev EY, Dontsova OS, Avdeeva VV, Kubasov AS, Zhdanov AP, Nikiforova SE, Goeva LV, Zhizhin KY, Malinina EA, Kuznetsov NT. Synthesis and Structures of Lead(II) Complexes with Substituted Derivatives of the Closo-Decaborate Anion with a Pendant N3 Group. Molecules. 2023; 28(24):8073. https://doi.org/10.3390/molecules28248073

Chicago/Turabian Style

Matveev, Evgenii Yu., Olga S. Dontsova, Varvara V. Avdeeva, Alexey S. Kubasov, Andrey P. Zhdanov, Svetlana E. Nikiforova, Lyudmila V. Goeva, Konstantin Yu. Zhizhin, Elena A. Malinina, and Nikolay T. Kuznetsov. 2023. "Synthesis and Structures of Lead(II) Complexes with Substituted Derivatives of the Closo-Decaborate Anion with a Pendant N3 Group" Molecules 28, no. 24: 8073. https://doi.org/10.3390/molecules28248073

APA Style

Matveev, E. Y., Dontsova, O. S., Avdeeva, V. V., Kubasov, A. S., Zhdanov, A. P., Nikiforova, S. E., Goeva, L. V., Zhizhin, K. Y., Malinina, E. A., & Kuznetsov, N. T. (2023). Synthesis and Structures of Lead(II) Complexes with Substituted Derivatives of the Closo-Decaborate Anion with a Pendant N3 Group. Molecules, 28(24), 8073. https://doi.org/10.3390/molecules28248073

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