Oxidative Addition of Diphenyldichalcogenides PhEEPh (E = S, Se, Te) to Low-Valent CN- and NCN-Chelated Organoantimony and Organobismuth Compounds

The reactions of the organoantimony­(I) compound L¹₄Sb₄ (<b>1</b>) (where L¹ = [<i>o</i>-C₆H₄(CHNC₆H₃(<i>i-</i>Pr)₂-2,6)]) with diphenyldichalcogenides PhEEPh (E = S, Se, or Te) gave compounds L¹Sb­(EPh)₂ (E = S (<b>2</b>), Se (<b>3</b>), Te (<b>4</b>)) as the result of the oxidative addition of the antimony­(I) atom across the chalcogen–chalcogen bond. The reaction of diphenyldichalcogenides PhEEPh with an <i>in situ</i> prepared organobismuth­(I) compound (via reaction of the parent chloride L¹BiCl₂ (<b>5</b>) with two equivalents of K­[B­(<i>s</i>-Bu)₃H]) gave surprisingly diorganobismuth compounds L¹₂Bi­(EPh) (E = S (<b>6</b>), Se (<b>7</b>), Te (<b>8</b>)) as the major products along with only a trace amount of the intended compounds L¹Bi­(EPh)₂ (E = S (<b>9</b>), Se (<b>10</b>), Te (<b>11</b>)). It turned out that this is the result of instability of <b>9</b>–<b>11</b> in solution, and their decomposition provided compounds <b>6</b>–<b>8</b>. The bismuth compounds containing the pincer-type ligand L² (L² = [<i>o,o</i>-C₆H₃(CH₂NMe₂)₂]) containing an extra donor pendant arm were studied with the aim to support their stability by an additional N→Bi interaction. Thus, <i>in situ</i> preparation of the organobismuth­(I) compound from L²BiCl₂ (<b>12</b>) and two equivalents of K­[B­(<i>s</i>-Bu)₃H] followed by the addition of PhEEPh gave compounds L²Bi­(EPh)₂ (E = S (<b>13</b>), Se (<b>14</b>), Te (<b>15</b>)). Compounds <b>13</b>–<b>15</b> showed no tendency for redistribution reaction, contrary to <b>9</b>–<b>11</b>, due to the rigid coordination of both nitrogen donor atoms of the ligand L² to the bismuth atom. All studied compounds were characterized by the help of ¹H and ¹³C NMR spectroscopy, by elemental analysis, and except compounds <b>4</b>, <b>14</b>, and <b>15</b> by single-crystal X-ray diffraction analyses

Stabilization of Three-Coordinated Germanium(II) and Tin(II) Cations by a Neutral Chelating Ligand

Treatment of the neutral 2-[C­(CH₃)N­(C₆H₃-2,6-^<i>i</i>Pr₂)]-6-(CH₃O)­C₆H₃N ligand (hereafter assigned as L) with SnCl₂ and GeCl₂ provided the ionic germanium­(II) and tin­(II) complexes [LGe^IICl]⁺­[Ge^IICl₃]⁻ (<b>1</b>) and [LSn^IICl]⁺­[Sn^IICl₃]⁻ (<b>2</b>), respectively, as the result of spontaneous dissociation of ECl₂ (E = Ge, Sn). The cationic parts [LE^IICl]⁺ of <b>1</b> and <b>2</b> contain three-coordinated germanium­(II) and tin­(II) atoms. In comparison, treatment of the ligand L with GeCl₄ and SnBr₄ yielded the germanium­(IV) and tin­(IV) complexes LGeCl₄ (<b>3</b>) and LSnBr₄ (<b>4</b>), respectively, and no dissociation process was observed. Compounds <b>1</b>–<b>4</b> were characterized by means of elemental analyses, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopies, and single-crystal X-ray diffraction analysis in (compounds <b>1</b> and <b>4</b>)

Stabilization of Three-Coordinated Germanium(II) and Tin(II) Cations by a Neutral Chelating Ligand

Treatment of the neutral 2-[C­(CH₃)N­(C₆H₃-2,6-^<i>i</i>Pr₂)]-6-(CH₃O)­C₆H₃N ligand (hereafter assigned as L) with SnCl₂ and GeCl₂ provided the ionic germanium­(II) and tin­(II) complexes [LGe^IICl]⁺­[Ge^IICl₃]⁻ (<b>1</b>) and [LSn^IICl]⁺­[Sn^IICl₃]⁻ (<b>2</b>), respectively, as the result of spontaneous dissociation of ECl₂ (E = Ge, Sn). The cationic parts [LE^IICl]⁺ of <b>1</b> and <b>2</b> contain three-coordinated germanium­(II) and tin­(II) atoms. In comparison, treatment of the ligand L with GeCl₄ and SnBr₄ yielded the germanium­(IV) and tin­(IV) complexes LGeCl₄ (<b>3</b>) and LSnBr₄ (<b>4</b>), respectively, and no dissociation process was observed. Compounds <b>1</b>–<b>4</b> were characterized by means of elemental analyses, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopies, and single-crystal X-ray diffraction analysis in (compounds <b>1</b> and <b>4</b>)

Intramolecularly Coordinated Stannanechalcogenones: X-ray Structure of [2,6-(Me₂NCH₂)₂C₆H₃](Ph)SnTe

The treatment of an intramolecularly coordinated organotin(IV) dichloride, [2,6-(Me₂NCH₂)₂C₆H₃](Ph)SnCl₂ (<b>1</b>), with Li₂E (E = S, Se, Te) afforded thermally stable dimeric diarylstannanethione [{2,6-(Me₂NCH₂)₂C₆H₃}(Ph)Sn(μ-S)]₂ (<b>2</b>) and monomeric diarylstannaneselone and -tellurone [{2,6-(Me₂NCH₂)₂C₆H₃}(Ph)SnE] (E = Se (<b>3</b>), Te (<b>4</b>)). Compounds <b>2</b>–<b>4</b> were characterized by means of elemental analyses and ¹H, ¹³C, ⁷⁷Se, ¹¹⁹Sn, and ¹²⁵Te NMR spectroscopy. The molecular structures of <b>2</b> and <b>4</b> were determined by single-crystal X-ray diffraction analysis. Solution NMR studies revealed dependence of the structure of compounds <b>2</b> and <b>3</b> on the solvent (C₆D₆ or CDCl₃). In addition, the synthesis of dimeric stannanetellurone [{2,6-(Me₂NCH₂)₂C₆H₃}(Bu)Sn(μ-Te)]₂ (<b>5</b>) showed an influence of the organic group R (R = Bu or Ph) on the structure of diorganotin(IV) tellurides <b>4</b> and <b>5</b>

Reactivity of N,C,N-Chelated Antimony(III) and Bismuth(III) Chlorides with Lithium Reagents: Addition vs Substitution

N,C,N-chelated antimony­(III) and bismuth­(III) chlorides L^1,2MCl₂ (<b>1</b>–<b>4</b>: for L¹, M = Sb (<b>1</b>), Bi (<b>3</b>); for L², M = Sb (<b>2</b>), Bi (<b>4</b>)) containing ligands L^1,2 (where L¹ = C₆H₃-2,6-(CHN-<i>t</i>-Bu)₂, L² = C₆H₃-2,6-(CHN-2′,6′-Me₂C₆H₃)₂) were prepared by reactions of lithium precursors with SbCl₃ or BiCl₃. The identities of <b>1</b>–<b>4</b> were established both in solution (¹H and ¹³C NMR spectroscopy) and, in the case of <b>1</b>–<b>3</b>, in the solid state using single-crystal X-ray diffraction analysis. Treatment of antimony derivatives <b>1</b> and <b>2</b> with 2 molar equiv of R′Li (R = Me, <i>n</i>-Bu, Ph) yielded the set of substituted 1,3-(R′)₂-2-R-7-(CHNR)-1<i>H</i>-2,1-benzazastiboles <b>5</b>–<b>10</b> (where R = <i>t</i>-Bu, 2,6-Me₂C₆H₃ and R′ = Me, <i>n</i>-Bu, Ph) as a result of a nucleophilic attack of one of the lithium compounds across the imino CN functionality. In contrast, analogous reactions between bismuth congeners <b>2</b> and <b>4</b> and R′Li (2 equiv, R′ = Me, Ph) gave L^1,2BiR′₂ (<b>11</b>–<b>13</b>: for L¹, R′ = Me (<b>11</b>), Ph (<b>12</b>); for L², R′ = Me (<b>13</b>)) as products of substitution of chlorine atoms. Compounds <b>5</b>–<b>13</b> were characterized by the help of ¹H and ¹³C NMR spectroscopy. The molecular structures of <b>8</b>, <b>9</b>, and <b>13</b> were unambiguously established using single-crystal X-ray diffraction analysis

Prototropic μ‑H^8,9 and μ‑H^9,10 Tautomers Derived from the [<i>nido</i>-5,6‑C₂B₈H₁₁]⁻ Anion

Reported is an unusual tautomeric behavior within the [<i>nido</i>-5,6-C₂B₈H₁₁]⁻ (<b>1a^–</b>) cage that has no precedence in the whole area of carborane chemistry. Isolated were two skeletal tautomers, anions [6-Ph-<i>nido</i>-5,6-C₂B₈H₁₀-μ^8,9]⁻ (<b>2d^–</b>) and [5,6-Me₂-<i>nido</i>-5,6-C₂B₈H₉-μ^9,10]⁻ (<b>3b^–</b>), which differ in the positioning of the open-face hydrogen bridge. Their structures have been determined by X-ray diffraction analyses. The <b>3b^–</b>structure is stabilized by intermolecular interaction involving Et₃NH⁺ and B8–B9 and H8 atoms in the solid phase; however, its dissolution in CD₃CN causes instant conversion to the more stable [5,6-Me₂-<i>nido</i>-5,6-C₂B₈H₉-μ^8,9]⁻ (<b>2b^–</b>) tautomer. The dynamic electron-correlation-based MP2/6-31G* computations suggest that the parent [<i>nido</i>-5,6-C₂B₈H₁₁-μ^8,9]⁻ (<b>2a^–</b>) tautomer is 3.9 kcal·mol^–1 more stable than the [<i>nido</i>-5,6-C₂B₈H₁₁-μ^9,10]⁻ (<b>3a^–</b>) counterpart and the μ^8,9 structure <b>2^–</b> is therefore the most stable tautomeric form in the solution, as was also demonstrated by multinuclear (¹H, ¹¹B, and ¹³C) NMR measurements on the whole series of C-substituted compounds

Simple Synthesis, Halogenation, and Rearrangement of <i>closo</i>-1,6‑C₂B₈H₁₀

Room-temperature reaction between <i>nido</i>-5,6-C₂B₈H₁₂ (<b>1</b>) and elemental iodine in the presence of triethylamine in CH₂Cl₂ gave the <i>closo</i>-1,6-C₂B₈H₁₀ (<b>2</b>) dicarbaborane in 85% yield. All the electrophilic halogenation reactions of <b>2</b> led exclusively to B(8)-substitution to get a series of 8-X-<i>closo</i>-1,6-C₂B₈H₉ (8X-<b>2</b>) derivatives (where X = Cl, Br, and I). Thermal rearrangements of <b>2</b> and 8X-<b>2</b> at ∼500–600 °C produced <i>closo</i>-1,10-C₂B₈H₁₀ (<b>3</b>) and a series of halo derivatives 2-X-<i>closo</i>-1,10-C₂B₈H₉ (2X-<b>3</b>), respectively. All the compounds isolated have been characterized by multinuclear (¹¹B, ¹H, and ¹³C) NMR spectroscopy, mass spectrometry, and elemental analyses, and the structure of 8Br-<b>2</b> was established by X-ray diffraction study

Carbon Insertion into <i>arachno-</i>6,9‑C₂B₈H₁₄ via Acyl Chlorides. Skeletal Alkylcarbonation (SAC) Reactions: A New Route for Tricarbollides

Reactions between <i>arachno</i>-6,9-C₂B₈H₁₄ (<b>1</b>) and selected acyl chlorides, RCOCl, in the presence of PS (PS = “proton sponge”, 1,8-dimethylamino naphthalene) in CH₂Cl₂ for 24 h at reflux, followed by in situ acidification with concentrated H₂SO₄ at 0 °C, generate a series of neutral alkyl and aryl tricarbollides 8-R-<i>nido</i>-7,8,9-C₃B₈H₁₁ (<b>2</b>) (where R = CH₃, <b>2a</b>; C₂H₅, <b>2b</b>; <i>n</i>-C₄H₉, <b>2c</b>; C₆H₅, <b>2d</b>; 4-Cl-C₆H₄, <b>2e</b>; 4-Br-C₆H₄, <b>2f</b>; 4-I-C₆H₄, <b>2g</b>; 1-C₁₀H₇, <b>2h</b>; and 2-C₁₀H₇, <b>2i</b>). The best yields were achieved for aryl derivatives (80–95%) while the yields of the corresponding alkyl substituted compounds are lower (60–70%). These skeletal alkylcarbonation (SAC) reactions are consistent with an aldol-type condensation between the RCO group and open-face hydrogen atoms on the dicarbaborane <b>1</b>, which is associated with the insertion of the carbonyl carbon atom into the structure of <i>arachno</i>-6,9-C₂B₈H₁₄ (<b>1</b>) under elimination of three extra hydrogen atoms as H₂O and HCl. The reactions thus result in an effective R–tricarbaborane cross-coupling. Individual compounds of structure <b>2</b> have been purified by chromatography on a silica gel support, using hexane as the mobile phase (<i>R</i>_F = ∼0.3). Deprotonation agents, such as NEt₃, NaOH, NaH, etc., convert tricarbaboranes <b>2</b> into the corresponding conjugated anions [8-R-<i>nido</i>-7,8,9-C₃B₈H₁₀]⁻ (<b>2</b>^–) which were isolated as salts with suitable countercations (for example, Et₃NH⁺, Tl⁺, NEt₄⁺, etc.). The compounds have been characterized by multinuclear (¹¹B, ¹H, and ¹³C) NMR spectroscopy, mass spectrometry, and elemental analyses. The structures of anions [8-R-<i>nido</i>-7,8,9-C₃B₈H₁₀]¯ (where R = C₆H₅, 4-I-C₆H₄ and 1-C₁₀H₇; <b>2a^–</b>, <b>2g^–</b>, and <b>2h</b>^–) and that of the neutral 8-(1-C₁₀H₇)-<i>nido</i>-7,8,9-C₃B₈H₁₁ (<b>2h</b>) have been established by X-ray diffraction analyses

Can Aromatic π-Clouds Complex Divalent Germanium and Tin Compounds? A DFT Study

The properties of various electron-deficient germylenes and stannylenes are investigated using density functional theory (DFT). The dominant electrophilic character of these divalent group IV compounds is demonstrated by computed DFT-based reactivity descriptors. Next, the interaction of selected model dihalogenated germylenes and stannylenes (GeX₂ and SnX₂, with X = F, Cl, Br, I) with a series of potential aromatic π-donors is studied; computed classical donor–acceptor σ-interactions with strong Lewis bases serve as a reference. In addition, natural bond orbital analyses were performed in order to study the interactions at the orbital level, consistently indicating that the most important interaction for the π-complexations is the overlap of the formal empty p-orbital on the germanium or the tin atom and the π-orbitals of the aromatic rings. Additional information is obtained from the extent of charge transfer from the π-donors toward the divalent tin and germanium compounds. The existence of a complexation interaction between the π-clouds of the aromatic rings and the divalent compounds is theoretically established. The strength of the π-complexation parallels the trends in electron-donating and electron-withdrawing character of the substituents on the aromatic compounds. Correlations of the total complexation energy with the NBO interaction energy confirm that this π-complexation is essentially an orbital-controlled interaction. In agreement with experimental data, σ-complexation is found to dominate over π-complexation

Carbon Insertion into <i>arachno-</i>6,9‑C₂B₈H₁₄ via Acyl Chlorides. Skeletal Alkylcarbonation (SAC) Reactions: A New Route for Tricarbollides

Reactions between <i>arachno</i>-6,9-C₂B₈H₁₄ (<b>1</b>) and selected acyl chlorides, RCOCl, in the presence of PS (PS = “proton sponge”, 1,8-dimethylamino naphthalene) in CH₂Cl₂ for 24 h at reflux, followed by in situ acidification with concentrated H₂SO₄ at 0 °C, generate a series of neutral alkyl and aryl tricarbollides 8-R-<i>nido</i>-7,8,9-C₃B₈H₁₁ (<b>2</b>) (where R = CH₃, <b>2a</b>; C₂H₅, <b>2b</b>; <i>n</i>-C₄H₉, <b>2c</b>; C₆H₅, <b>2d</b>; 4-Cl-C₆H₄, <b>2e</b>; 4-Br-C₆H₄, <b>2f</b>; 4-I-C₆H₄, <b>2g</b>; 1-C₁₀H₇, <b>2h</b>; and 2-C₁₀H₇, <b>2i</b>). The best yields were achieved for aryl derivatives (80–95%) while the yields of the corresponding alkyl substituted compounds are lower (60–70%). These skeletal alkylcarbonation (SAC) reactions are consistent with an aldol-type condensation between the RCO group and open-face hydrogen atoms on the dicarbaborane <b>1</b>, which is associated with the insertion of the carbonyl carbon atom into the structure of <i>arachno</i>-6,9-C₂B₈H₁₄ (<b>1</b>) under elimination of three extra hydrogen atoms as H₂O and HCl. The reactions thus result in an effective R–tricarbaborane cross-coupling. Individual compounds of structure <b>2</b> have been purified by chromatography on a silica gel support, using hexane as the mobile phase (<i>R</i>_F = ∼0.3). Deprotonation agents, such as NEt₃, NaOH, NaH, etc., convert tricarbaboranes <b>2</b> into the corresponding conjugated anions [8-R-<i>nido</i>-7,8,9-C₃B₈H₁₀]⁻ (<b>2</b>^–) which were isolated as salts with suitable countercations (for example, Et₃NH⁺, Tl⁺, NEt₄⁺, etc.). The compounds have been characterized by multinuclear (¹¹B, ¹H, and ¹³C) NMR spectroscopy, mass spectrometry, and elemental analyses. The structures of anions [8-R-<i>nido</i>-7,8,9-C₃B₈H₁₀]¯ (where R = C₆H₅, 4-I-C₆H₄ and 1-C₁₀H₇; <b>2a^–</b>, <b>2g^–</b>, and <b>2h</b>^–) and that of the neutral 8-(1-C₁₀H₇)-<i>nido</i>-7,8,9-C₃B₈H₁₁ (<b>2h</b>) have been established by X-ray diffraction analyses