5 research outputs found

    Understanding C鈥揌 Bond Activation on a Diruthenium(I) Platform

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    Activation of the C鈥揌 bond at the axial site of a [Ru<sup>I</sup>鈥揜u<sup>I</sup>] platform has been achieved. Room-temperature treatment of 2-(R-phenyl)-1,8-naphthyridine (R = H, F, OMe) with [Ru<sub>2</sub>(CO)<sub>4</sub>(CH<sub>3</sub>CN)<sub>6</sub>]颅[BF<sub>4</sub>]<sub>2</sub> in CH<sub>2</sub>Cl<sub>2</sub> affords the corresponding diruthenium颅(I) complexes, which carry two ligands, one of which is orthometalated and the second ligand engages an axial site via a Ru路路路C鈥揌 interaction. Reaction with 2-(2-<i>N</i>-methylpyrrolyl)-1,8-naphthyridine under identical conditions affords another orthometalated/nonmetalated (<i>om</i>/<i>nm</i>) complex. At low temperature (4 掳C), however, a nonmetalated complex is isolated that reveals axial Ru路路路C鈥揌 interactions involving both ligands at sites <i>trans</i> to the Ru鈥揜u bond. A nonmetalated (<i>nm</i>/<i>nm</i>) complex was characterized for 2-pyrrolyl-1,8-naphthyridine at room temperature. Orthometalation of both ligands on a single [Ru鈥揜u] platform could not be accomplished even at elevated temperature. X-ray metrical parameters clearly distinguish between the orthometalated and nonmetalated ligands. NMR investigation reveals the identity of each proton and sheds light on the nature of [Ru鈥揜u]路路路C鈥揌 interactions (preagostic/agostic). An electrophilic mechanism is proposed for C鈥揌 bond cleavage that involves a C颅(p<sub>蟺</sub>)鈥揌 鈫 蟽* [Ru鈥揜u] interaction, resulting in a Wheland-type intermediate. The heteroatom stabilization is credited to the isolation of nonmetalated complexes for pyrrolyl C鈥揌, whereas lack of such stabilization for phenyl C鈥揌 causes rapid proton elimination, giving rise to orthometalation. NPA charge analysis suggests that the first orthometalation makes the [Ru鈥揜u] core sufficiently electron rich, which does not allow significant interaction with the other axial C鈥揌 bond, making the second metalation very difficult

    Understanding C鈥揌 Bond Activation on a Diruthenium(I) Platform

    No full text
    Activation of the C鈥揌 bond at the axial site of a [Ru<sup>I</sup>鈥揜u<sup>I</sup>] platform has been achieved. Room-temperature treatment of 2-(R-phenyl)-1,8-naphthyridine (R = H, F, OMe) with [Ru<sub>2</sub>(CO)<sub>4</sub>(CH<sub>3</sub>CN)<sub>6</sub>]颅[BF<sub>4</sub>]<sub>2</sub> in CH<sub>2</sub>Cl<sub>2</sub> affords the corresponding diruthenium颅(I) complexes, which carry two ligands, one of which is orthometalated and the second ligand engages an axial site via a Ru路路路C鈥揌 interaction. Reaction with 2-(2-<i>N</i>-methylpyrrolyl)-1,8-naphthyridine under identical conditions affords another orthometalated/nonmetalated (<i>om</i>/<i>nm</i>) complex. At low temperature (4 掳C), however, a nonmetalated complex is isolated that reveals axial Ru路路路C鈥揌 interactions involving both ligands at sites <i>trans</i> to the Ru鈥揜u bond. A nonmetalated (<i>nm</i>/<i>nm</i>) complex was characterized for 2-pyrrolyl-1,8-naphthyridine at room temperature. Orthometalation of both ligands on a single [Ru鈥揜u] platform could not be accomplished even at elevated temperature. X-ray metrical parameters clearly distinguish between the orthometalated and nonmetalated ligands. NMR investigation reveals the identity of each proton and sheds light on the nature of [Ru鈥揜u]路路路C鈥揌 interactions (preagostic/agostic). An electrophilic mechanism is proposed for C鈥揌 bond cleavage that involves a C颅(p<sub>蟺</sub>)鈥揌 鈫 蟽* [Ru鈥揜u] interaction, resulting in a Wheland-type intermediate. The heteroatom stabilization is credited to the isolation of nonmetalated complexes for pyrrolyl C鈥揌, whereas lack of such stabilization for phenyl C鈥揌 causes rapid proton elimination, giving rise to orthometalation. NPA charge analysis suggests that the first orthometalation makes the [Ru鈥揜u] core sufficiently electron rich, which does not allow significant interaction with the other axial C鈥揌 bond, making the second metalation very difficult

    Potential Protecting Group Strategy for Disila Analogues of Vinyllithiums: Synthesis and Reactivity of a 2,4,6-Trimethoxyphenyl-Substituted Disilene

    No full text
    Proof of concept for the protection of the nucleophilic functionality of disilenides顥竏isila analogues of vinyllithium顥竪ith preservation of the Si顥籗i bond is reported. 1-Iodo-2,4,6-trimethoxybenzene (TMOP-I) reacts with lithium tris颅(2,4,6-triisopropylphenyl)颅disilenide (<b>1</b>), affording the disilene Tip<sub>2</sub>Si顥籗i颅(Tip)颅TMOP (<b>2</b>) in high yield. The presence of the TMOP group in disilene <b>2</b> enables the regioselective addition of polar substrates to the Si顥籗i double bond, including water, ammonia, acetylenes, and isocyanides. NMR spectroscopic analysis of the reductive cleavage of the TMOP group and subsequent trapping of the corresponding disilenides with Me<sub>3</sub>SiCl reveals KC<sub>8</sub> as a highly appropriate reducing agent for the selective deprotection

    Potential Protecting Group Strategy for Disila Analogues of Vinyllithiums: Synthesis and Reactivity of a 2,4,6-Trimethoxyphenyl-Substituted Disilene

    No full text
    Proof of concept for the protection of the nucleophilic functionality of disilenides顥竏isila analogues of vinyllithium顥竪ith preservation of the Si顥籗i bond is reported. 1-Iodo-2,4,6-trimethoxybenzene (TMOP-I) reacts with lithium tris颅(2,4,6-triisopropylphenyl)颅disilenide (<b>1</b>), affording the disilene Tip<sub>2</sub>Si顥籗i颅(Tip)颅TMOP (<b>2</b>) in high yield. The presence of the TMOP group in disilene <b>2</b> enables the regioselective addition of polar substrates to the Si顥籗i double bond, including water, ammonia, acetylenes, and isocyanides. NMR spectroscopic analysis of the reductive cleavage of the TMOP group and subsequent trapping of the corresponding disilenides with Me<sub>3</sub>SiCl reveals KC<sub>8</sub> as a highly appropriate reducing agent for the selective deprotection

    Mixed Ligated Tris(amidinate)dimolybdenum Complexes as Catalysts for Radical Addition of CCl<sub>4</sub> to 1鈥慔exene: Leaving Ligand Lability Controls Catalyst Activity

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    We synthesized a series of mixed ligated tris颅(amidinate)颅dimolybdenum complexes, namely, [Mo<sub>2</sub>(DAniF)<sub>3</sub>(L)] [DAniF = <i>N</i>,<i>N</i>鈥-di颅(<i>p</i>-anisyl)颅formamidinate; L = acetate (OAc; <b>1a</b>), <i>m</i>-diphenylphosphino benzoate (<i>m</i>-PPh<sub>2</sub>Bz; <b>1b</b>), nicotinate (Nico; <b>1c</b>), benzoate (Bz; <b>1d</b>), 3-furoate (3-Furo; <b>1e</b>), isonicotinate (IsoNico; <b>1f</b>), and trifluoromethanesulfonate (OTf; <b>1g</b>)], which served as catalysts for radical addition of CCl<sub>4</sub> to 1-hexene to give 1,1,1,3-tetrachloroheptane. These mixed ligated complexes <b>1a</b>鈥<b>g</b> afforded the higher yield of the radical addition product than a homoleptic DAniF complex, [Mo<sub>2</sub>(DAniF)<sub>4</sub>] (<b>2</b>). Among them, complexes <b>1a</b> and <b>1g</b> gave the radical addition product quantitatively after 9 h with a short induction period. When complexes <b>1a</b> and <b>1g</b> were treated with CCl<sub>4</sub>, we detected the mixed-valence Mo<sub>2</sub>(II/III) complex, [Mo<sub>2</sub>(DAniF)<sub>3</sub>Cl<sub>2</sub>] (<b>4</b>), in electrospray ionization mass spectrometry measurements, indicating that the leaving nature of the L ligands was a crucial factor for initiating the catalytic reaction: the catalytic activity of the carboxylate-bridged complex <b>1a</b> and the triflate-bridged complex <b>1g</b> in the initial 30 min highly depended on the ligand-exchange rate of L, as estimated by monitoring the reaction with CCl<sub>4</sub> in pyridine, giving the pyridine adduct complex, [Mo<sub>2</sub>(DAniF)<sub>3</sub>Cl颅(py)] (<b>3</b>)
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