Stabilization of 2H-phospholes by complexation. A phosphorus-carbon double bond acting as a four-electron donor

Holand, Serge; Charrier, Claude; Mathey, François; Fischer, Jean; Mitschler, A.

doi:10.1021/ja00315a081

Cited by 47 publications

(8 citation statements)

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“…11 Although some η 1 and η 2 tungsten phosphaalkene complexes have been described, there is not much NMR data available. 12 In the IR spectra of uncomplexed 1-aza-3-phosphaallenes a strong band between 1830 and 1915 cm -1 due to the asymmetric stretch of the PdCdN unit has been found to be characteristic for this class of compounds. 2a In the IR spectra of η 2 (P,C)-and η 2 (CN)-coordinated 1-aza-3-phosphaallene complexes a strong band in the region 1800-2000 cm -1 is absent.…”

Section: Resultsmentioning

confidence: 96%

Photochemical and Thermal Reactions of a 2H-Azaphosphirene Complex with Isonitriles

et al. 2005

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Photochemical ring opening of {2-[bis(trimethylsilyl)methyl]-3-phenyl-2H-azaphosphirene-κP}pentacarbonyltungsten(0) (1) in diethyl ether in the presence of tert-butyl isocyanide (2) yields the η 1 -1-aza-3-phosphaallene complex 4 at low temperature (-30 °C), the formation of which is explained via a 1,1-addition of 2 with the transiently formed terminal phosphinidene complex 3. Complex 4 decomposed slowly at ambient temperature to furnish the [bis(trimethylsilyl)methyl]cyanophosphane complex 5 and isobutene. The same result was obtained via thermal ring opening of complex 1 at high temperature. In contrast, thermolysis of 1 in the presence of cyclohexyl isocyanide ( 7) afforded the N-cyclohexyl-substituted η 1 -1-aza-3-phosphaallene complex 8. Complexes 4, 5, and 8 were unambiguously characterized by NMR and IR spectroscopy; the structure of complex 5 was established by X-ray crystal structure analysis. The structure of 5 and the energetics of its formation via decomposition of 4 were studied by DFT calculations, thus confirming the proposed reaction course.

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Section: Resultsmentioning

confidence: 96%

Photochemical and Thermal Reactions of a 2H-Azaphosphirene Complex with Isonitriles

et al. 2005

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“…It therefore appears that after the formation of the cis mixed-ligand complex, at an elevated temperature, the coordinated 1 H -phosphole rearranges to the 2 H -phosphole within the metal coordination sphere prior to the [4+2] cycloaddition to produce the highly reactive hot diene. The fact that [1,5] sigmatropic shifts occur for a P-coordinated phosphole has been demonstrated for hydrogen . The reactive coordinated 2 H -phosphole spontaneously adds to the crotyl unit acting as the dienophile to give the Diels−Alder [4+2] cycloaddition product.…”

Section: Discussionmentioning

confidence: 99%

Intramolecular [4+2] Diels−Alder Cycloaddition of a 2H-Phosphole to Coordinated Unsaturated Phosphines, Phospholes, and an Arsine

1997

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Stereoselective [4+2] Diels−Alder cycloadditions occur between unsaturated tertiary phosphine, phosphole, and arsine molybedenum carbonyl complexes, e.g., (Ph2E-trans-CH2CHCHCH3)Mo(CO)5 [E = P, As] and 3,4-dimethyl-1-phenylphosphole (DMPP). The coordinated DMPP undergoes a [1,5] phenyl migration at about 145 °C prior to or concomitant with the [4+2] intramolecular cycloaddition reaction with the alkene moiety of the dienophile to produce a new class of conformationally rigid bidentate ligands containing the 1-phosphanorbornene bicyclic ring system. The characteristic 1H, 13C{1H}, and 31P{1H} NMR spectroscopic features of these compounds are described. Crystal structures of most of the new compounds are reported.

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“…Adding small amounts of KO t Bu (5 equiv) to a THF solution of complex 14 at 0 °C (period of 80 min) and warming to ambient temperature (18 h) resulted in a color change from yellow to dark red and the formation of complex 15 showing a 31 P-resonance at 117.5 ppm and a very low phosphorus−tungsten coupling of 172.2 Hz; such values are similar to those observed for phospholide complexes (cf. ref ). The crude product mixture was analyzed with CI (methane) mass spectra and the molecular ion was observed, thus providing evidence for the nature of 15 as a new 1,3,2-diazaphospholide complex (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Multifunctional 2H-1,2-Azaphosphole Complexes: A Good Starting Point for the Synthesis of Functional 1,2-Azaphospholide Complexes?

et al. 2003

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The thermolysis of P-functionalized 7-phosphanorbornadiene tungsten complexes 3a−d in o-xylene at 120 °C in the presence of various carbonitriles and dimethyl acetylenedicarboxylate (DMAD) has been investigated. The reaction of complex 3a, 1-piperidino carbonitrile, and DMAD yielded a product mixture, whereby 2H-1,2-azaphosphole complex 6 was formed in ca. 40−45% yield together with diazaphosphole complexes 7 (ca. 10−15%) and 8 (ca. 10−15%) and other nonidentified products (ca. 30%). Unfortunately, none of these products could be separated by column chromatography. In marked contrast, reactions of 7-phosphanorbornadiene tungsten complexes 3a−d with triphenylphosphane-imino carbonitrile and DMAD led to P-functionalized 2H-1,2-azaphosphole complexes 11a−d in good to excellent yields. Preliminary investigations of decomplexation reactions revealed a remarkable thermal stability of 11a−d: no reaction occurred with bis(diphenylphosphino)ethane (DPPE) at 140 °C. Preliminary studies of exocyclic P−C bond cleavage reactions of 2H-1,2-azaphosphole complexes 11a,b using potassium tert-butanolate (KOtBu) showed instantaneous reactions and color change from yellow to dark red; an intermediate was detected by 31P NMR spectroscopy. Treatment with an excess of methyl iodide led to one major product, which, most probably, is the N-methyl-substituted 1H-1,2-azaphosphole complex 13; unfortunately, chromatography failed and it could only be observed by 31P NMR spectroscopy. A comparative study on P−C bond cleavage/methylation reactions using monofunctional 2H-1,3,2-diazaphosphole complex 14 and the system KOtBu/methyl iodide showed the selective formation of the P-methyl-substituted 2H-1,3,2-diazaphosphole complex 16; complexes 14 and 16 were prepared using the Cu(I)Cl route. Complexes 11a−d, 14, and 16 were characterized by elemental analyses, NMR, UV/vis, IR, and mass spectroscopy and, in addition, by single-crystal X-ray diffraction in the case of 11a−d. Additionally, we investigated selected isomers of lithium and potassium 1,2-azaphospholides by ab initio calculations using HF and MP2/6-311++G(2d,p) level of theory; stability, structure, and aromaticity aspects are discussed.

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Stabilization of 2H-phospholes by complexation. A phosphorus-carbon double bond acting as a four-electron donor

Cited by 47 publications

References 1 publication

Photochemical and Thermal Reactions of a 2H-Azaphosphirene Complex with Isonitriles

Photochemical and Thermal Reactions of a 2H-Azaphosphirene Complex with Isonitriles

Intramolecular [4+2] Diels−Alder Cycloaddition of a 2H-Phosphole to Coordinated Unsaturated Phosphines, Phospholes, and an Arsine

Multifunctional 2H-1,2-Azaphosphole Complexes: A Good Starting Point for the Synthesis of Functional 1,2-Azaphospholide Complexes?

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