37 research outputs found

    Probing the Group Tolerance of a Li/Cl Phosphinidenoid Complex Using Alkenyl-Substituted Aldehydes

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    Reaction of the Li/Cl phosphinidenoid pentacarbonyltungsten complex <b>2</b> (R = CH­(SiMe<sub>3</sub>)<sub>2</sub>) with unsaturated aldehydes <b>3</b>, <b>4</b>, <b>9</b>, <b>10</b>, and <b>13</b> yielded the new oxaphosphirane complexes <b>5</b>, <b>7</b>, <b>11</b>, <b>12</b>, and <b>14</b> and thus revealed a clear preference for CO vs CC bond addition (i) and for 1,2- vs 1,4 addition (ii). Complexes were characterized by NMR, IR spectroscopy, and mass spectrometry and, in the case of <b>14a</b>, by single-crystal X-ray analysis

    Novel Spirooxaphosphirane Complexes

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    Reaction of a transient Li/Cl phosphinidenoid pentacarbonyltungsten complex <b>3</b> (R = C<sub>5</sub>Me<sub>5</sub>) with 3-oxetanone, dihydro-3­(2<i>H</i>)-furanone, and dihydro-4<i>H</i>-pyran-4-one led to the novel spirooxaphosphirane complexes <b>5</b>, <b>7a</b>,<b>b</b>, and <b>9a</b>,<b>b</b> having an additional oxygen atom in the ring system, while δ-valerolactone furnished selectively the P,C-cage complex <b>10</b>. All complexes have been characterized by heteronuclear NMR and mass spectrometry and by single-crystal X-ray analysis in the case of <b>7a</b> and <b>9a</b>

    <i>C</i>‑Trifluoromethyl-Substituted 1,2-Oxaphosphetane Complexes: Synthetic and Structural Study

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    Recently, the first synthetic route to 1,2-oxaphosphetane complexes was described, but the formation of too many isomers was a clear drawback and hampered further studies. Herein, we present significant advances with this problem using trifluoromethyl epoxide (<b>4</b>), 1,1′-bis­(trifluoromethyl) epoxide (<b>5</b>), and differently substituted Li/Cl phosphinidenoid complexes <b>1</b>–<b>3</b> (R = CH­(SiMe<sub>3</sub>)<sub>2</sub>, CPh<sub>3</sub>, C<sub>5</sub>Me<sub>5</sub>), thus giving 1,2-oxaphosphetane complexes <b>6</b>–<b>10</b> with high selectivity

    Acid-Induced Reactions of 1,2-Oxaphosphetane Complexes

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    Selective P–O bond activation of 1,2-oxaphosphetane complexes [(OC)<sub>5</sub>W­(P­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­CH<sub>2</sub>CRR′O)] (R/R′ = H/H (<b>1a</b>), H/CH<sub>3</sub> (<b>1b</b>), H/CF<sub>3</sub> (<b>1c</b>), CF<sub>3</sub>/CF<sub>3</sub> (<b>1d</b>)) was achieved using different Brønsted acids. In case of acids with nucleophilic anions, such as HCl and HBF<sub>4</sub>·OEt<sub>2</sub>, the corresponding halophosphane complexes [(OC)<sub>5</sub>W­(XP­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­CH<sub>2</sub>CRR′OH] (X = Cl (<b>2a</b>–<b>c</b>), F (<b>3c</b>,<b>d</b>)) resulted as ring-opened products; <b>2b</b> could be closed again with <sup>t</sup>BuLi/12-crown-4. In contrast, trifluoromethanesulfonic acid could be used to initiate either a ring-opening hydrolysis with a subsequent cleavage of the P–M bond to yield PH­(O)­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­{CH<sub>2</sub>C­(CF<sub>3</sub>)<sub>2</sub>OH} (<b>7</b>) or, in the presence of nitriles, a ring expansion yielding [(OC)<sub>5</sub>W­(P­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­CH<sub>2</sub>CH<sub>2</sub>OCRN)] (R = CH<sub>3</sub> (<b>5a</b>), Ph (<b>5b</b>), C­(CH<sub>3</sub>)<sub>3</sub> (<b>5c</b>)). P–O bond cleavage in <b>1a</b> was achieved using the Lewis acidic catechol­(chloro)­borane to give [(OC)<sub>5</sub>W­(P­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­CH<sub>2</sub>CH­(CH<sub>3</sub>)­OBcat}­Cl)] (<b>8</b>; cat = catechol)

    Acid-Induced Reactions of 1,2-Oxaphosphetane Complexes

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    Selective P–O bond activation of 1,2-oxaphosphetane complexes [(OC)<sub>5</sub>W­(P­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­CH<sub>2</sub>CRR′O)] (R/R′ = H/H (<b>1a</b>), H/CH<sub>3</sub> (<b>1b</b>), H/CF<sub>3</sub> (<b>1c</b>), CF<sub>3</sub>/CF<sub>3</sub> (<b>1d</b>)) was achieved using different Brønsted acids. In case of acids with nucleophilic anions, such as HCl and HBF<sub>4</sub>·OEt<sub>2</sub>, the corresponding halophosphane complexes [(OC)<sub>5</sub>W­(XP­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­CH<sub>2</sub>CRR′OH] (X = Cl (<b>2a</b>–<b>c</b>), F (<b>3c</b>,<b>d</b>)) resulted as ring-opened products; <b>2b</b> could be closed again with <sup>t</sup>BuLi/12-crown-4. In contrast, trifluoromethanesulfonic acid could be used to initiate either a ring-opening hydrolysis with a subsequent cleavage of the P–M bond to yield PH­(O)­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­{CH<sub>2</sub>C­(CF<sub>3</sub>)<sub>2</sub>OH} (<b>7</b>) or, in the presence of nitriles, a ring expansion yielding [(OC)<sub>5</sub>W­(P­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­CH<sub>2</sub>CH<sub>2</sub>OCRN)] (R = CH<sub>3</sub> (<b>5a</b>), Ph (<b>5b</b>), C­(CH<sub>3</sub>)<sub>3</sub> (<b>5c</b>)). P–O bond cleavage in <b>1a</b> was achieved using the Lewis acidic catechol­(chloro)­borane to give [(OC)<sub>5</sub>W­(P­{CH­(SiMe<sub>3</sub>)<sub>2</sub>}­CH<sub>2</sub>CH­(CH<sub>3</sub>)­OBcat}­Cl)] (<b>8</b>; cat = catechol)

    A New Route to Phosphaalkene Chelate Complexes: SET Deoxygenation of Oxaphosphirane Complexes Followed by Intramolecular CO Substitution

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    Synthesis and SET deoxygenation of oxaphosphirane complexes <b>1a</b>–<b>e</b> of the general formula [(CO)<sub>5</sub>M­{R<sup>1</sup>R<sup>2</sup>C–O-PCH­(SiMe<sub>3</sub>)<sub>2</sub>}] (<b>1a</b>: M = W, R<sup>1</sup> = Me, R<sup>2</sup> = <i>o</i>-py; <b>1b</b>: M = W, R<sup>1</sup> = H, R<sup>2</sup> = <i>o</i>-py; <b>1c</b>: M = Mo, R<sup>1</sup> = H, R<sup>2</sup> = <i>o</i>-py; <b>1d</b>: M = Cr, R<sup>1</sup> = H, R<sup>2</sup> = <i>o</i>-py; <b>1e</b>: M = W, R<sup>1</sup>,R<sup>2</sup> = Me) using the system TiCpCl<sub>3</sub>/Zn led to the formation of phosphaalkene complexes <b>2a</b>–<b>e</b>. In the case of <b>2e</b>, [{CpTi­(Cl)­O}<sub>4</sub>] (<b>4</b>), a product of the SET deoxygenation process, was isolated. Subsequent CO extrusion/substitution of <b>2a</b>–<b>d</b> yielded the phosphaalkene chelate complexes <b>3a</b>–<b>d</b> under mild conditions. NMR, IR and MS data as well as X-ray structures of complexes <b>1a</b>,<b>b</b>, <b>2e</b>, and <b>3a</b>,<b>b</b> will be reported

    (Bis(terpyridine))copper(II) Tetraphenylborate: A Complex Example for the Jahn–Teller Effect

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    The surprisingly complicated crystal structure of (bis­(terpyridine))­copper­(II) tetraphenylborate [Cu­(tpy)<sub>2</sub>]­(BPh<sub>4</sub>)<sub>2</sub> (tpy = 2,2′:6′,2″-terpyridine) consists of six crystallographically independent [Cu­(tpy)<sub>2</sub>]<sup>2+</sup> complexes. At ambient temperature, five out of six [Cu<sup>II</sup>N<sub>6</sub>] chromophores appear to be compressed octahedra, while at 100 K, four exhibit elongated and only two compressed octahedral geometry. Temperature dependent single crystal UV/vis (100, 298 K) and EPR measurements (20, 100, 298 K) as well as AOM calculations suggest that the octahedra which show apparently compressed octahedral geometry (XRD) result from dynamic Jahn–Teller behavior of elongated octahedra [Cu<sup>II</sup>N<sub>6</sub>]. The detailed correlation of structural and spectroscopic data allows an understanding of the strongly solvent-dependent structures of the [Cu­(tpy)<sub>2</sub>]<sup>2+</sup> complex in solution

    Regioselective Sulfonylation and <i>N</i>- to <i>O</i>‑Sulfonyl Migration of Quinazolin-4(3<i>H</i>)‑ones and Analogous Thienopyrimidin-4(3<i>H</i>)‑ones

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    The sulfonylation of quinazolin-4­(3<i>H</i>)-ones and related tetrahydrobenzothieno­[2,3-<i>d</i>]­pyrimidin-4­(3<i>H</i>)-ones with mesyl, tosyl, and <i>p</i>-cyanobenzenesulfonyl chloride was studied. A hydrogen substituent at 2-position directed the sulfonyl group to the N-3 position, while alkylsulfanyl or amino substituents led to sulfonylation of the carbonyl oxygen. The latter effect was attributed to steric influence and the positive mesomeric effect of the 2-substituent. An access to <i>N</i>-sulfonylated 2-substituted regioisomers was established. An unexpected 1,3-sulfonyl migration was observed and further analyzed. This process occurred as an intramolecular <i>N</i>- to <i>O</i>-shift as verified by kinetic and crossover experiments

    Synthesis of <i>P</i>‑CPh<sub>3</sub> Substituted Spirooxaphosphirane Complexes: Steric Effects Dominate the Product Formation

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    The reaction of Li/Cl phosphinidenoid pentacarbonyltungsten complex <b>2</b> with cyclobutanone and 3-oxetanone led to new, stable spirooxaphosphirane complexes <b>3</b> and <b>4</b>. In contrast, formation of O–H insertion products <b>5</b> and <b>6</b> was the preferred reaction pathway in case of cyclopentanone and cyclohexanone; this is in contrast to spirooxaphosphirane complex formation with sterically less demanding P-substituents. All complexes have been characterized by heteronuclear NMR spectroscopy and single crystal X-ray analysis in case of <b>3</b> and <b>4</b>
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