Cycloaddition reaction of parent ketene with 1,3-dipolar adducts of [RP-W(CO)<sub>5</sub>] and electron-rich nitriles

Nils Hoffmann; Rainer Streubel; Louis Ricard; Ngoc Hoa Tran Huy; François Mathey

doi:10.1016/j.crci.2003.06.010

Cycloaddition reaction of parent ketene with 1,3-dipolar adducts of [RP-W(CO)₅] and electron-rich nitriles

Nils Hoffmann ¹ ; Rainer Streubel ¹ ; Louis Ricard ² ; Ngoc Hoa Tran Huy ² ; François Mathey ²

¹ Institut für Anorganische und Analytische Chemie der Technischen Universität Braunschweig, P.O. Box 3329, 38023 Braunsweig, Germany
² Laboratoire ‘Hétéroéléments et Coordination’, UMR CNRS 7653, DCPH, École polytechnique, 91128 Palaiseau cedex, France

Comptes Rendus. Chimie, Volume 7 (2004) no. 8-9, pp. 927-930.

Résumés

Anglais
Français

The reaction of parent ketene with the 1,3-dipolar adducts of electrophilic terminal phosphinidene complexes [RP-W(CO)₅] and activated nitriles yields the previously unknown 4,5-dihydro–1,3,4-oxazaphosphole ring.

Les complexes de phosphinidène [RP-W(CO)₅] donnent un adduit dipolaire 1,3 avec les nitriles activés. Cet adduit réagit avec le cétène parent pour donner le cycle dihydro–4,5-oxazaphosphole–1,3,4, décrit ici pour la première fois.

Métadonnées

Reçu le : 2003-01-26
Accepté le : 2003-06-17
Publié le : 2004-07-28

DOI : 10.1016/j.crci.2003.06.010

Keywords: Phosphinidene complexes, Ketene, Cycloaddition
Mots clés : Complexes de phosphinidène, Cétène, Cycloaddition

Affiliations des auteurs :

Nils Hoffmann ¹ ; Rainer Streubel ¹ ; Louis Ricard ² ; Ngoc Hoa Tran Huy ² ; François Mathey ²

¹ Institut für Anorganische und Analytische Chemie der Technischen Universität Braunschweig, P.O. Box 3329, 38023 Braunsweig, Germany
² Laboratoire ‘Hétéroéléments et Coordination’, UMR CNRS 7653, DCPH, École polytechnique, 91128 Palaiseau cedex, France

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     title = {Cycloaddition reaction of parent ketene with 1,3-dipolar adducts of {[RP-W(CO)\protect\textsubscript{5}]} and electron-rich nitriles},
     journal = {Comptes Rendus. Chimie},
     pages = {927--930},
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Nils Hoffmann; Rainer Streubel; Louis Ricard; Ngoc Hoa Tran Huy; François Mathey. Cycloaddition reaction of parent ketene with 1,3-dipolar adducts of [RP-W(CO)₅] and electron-rich nitriles. Comptes Rendus. Chimie, Volume 7 (2004) no. 8-9, pp. 927-930. doi : 10.1016/j.crci.2003.06.010. https://comptes-rendus.academie-sciences.fr/chimie/articles/10.1016/j.crci.2003.06.010/

Version originale du texte intégral

1 Introduction

It has been known for some time that ethoxyacetylene and its derivatives decompose to ketenes and ethylene upon heating [1–3]. Some time ago, we studied the reaction of ethoxyacetylene with electrophilic terminal phosphinidene complexes 2 as generated from the appropriate 7-phosphanorbornadiene complexes 1 [4]. To our surprise, we did not get the expected 3-membered phosphirene complexes 3, but instead the C-unsubstituted phosphirane complexes 4 resulting from the trapping of ethylene as produced by the thermal decomposition of ethoxyacetylene (Eq. (1)).

It was clear that parent ketene was a by-product of this reaction, but could not be trapped by the electrophilic terminal phosphinidene complexes.

It is also known for some time that electrophilic terminal phosphinidene complexes react with electron-rich nitriles to give 1,3-dipolar species 5, in which the phosphorus centre is nucleophilic (Eq. (2)) [5].

Thus it was tempting to add an electron-rich nitrile to the reaction depicted in Eq. (1). We expected that 5 would not react any more with ethylene but, instead, would selectively trap parent ketene. The experiments were carried out with N-cyano-P,P,P-triphenylphosphazene 6 [6]. The results are shown in Eq. (3) and confirm our expectations.

The formula of 7a was established by X-ray crystal structure analysis (Fig. 1). The compound incorporates a 1,3,4-oxazaphosphole ring that, to our knowledge, has never been described in the literature until now [7]. The structural parameters deserve no special comments. The ¹³C NMR spectrum suggests that the very contracted exocyclic C=C double bond (C=C 1.303(4) Å) is highly polarized δ ( $\underline{C}$ =CH₂) 161.5, δ (C= $\underline{C}$ H₂) 96.5.

Fig. 1
ORTEP drawing of one molecule of 7a. Selected bond lengths (6 Å) and angles (deg): W(2)–P(3) 2.4890(8), P(3)–C(4) 1.833(3), C(4)–C(5) 1.303(4), C(4)–O(2) 1.394(4), O(2)–C(6) 1.391(4), C(6)–W(4) 1.340(4), W(4)–P(4) 1.603(3), C(6)–W(3) 1.298(4), W(3)–P(3) 1.683(3) ; W(3)–P(3)–C(4) 91.9(1), P(3)–C(4)–O(2) 106.8(2), C(4)–O(2)–C(6) 111.1(2), O(2)–C(6)–W(3) 119.1(3), C(6)–W(3)–P(3) 111.0(2).

2 Experimental section

NMR spectra were recorded on a multinuclear Bruker AVANCE 300 MHz spectrometer operating at 300.13 MHz for ¹H, 75.47 for ¹³C and 121.50 MHz for ³¹P. Chemical shifts are expressed in parts per million (ppm) downfield from internal tetramethylsilane (¹H and ¹³C) and external 85% aqueous H₃PO₄ (³¹P).

2.1 General procedure for the synthesis of 1,3,4-oxazaphospholes 7a,b

To a solution of 7-phosphanorbornadiene complexes (1.2 mmol each), dissolved in 1,2-dichlorobenzene (4 ml), N-cyano-P,P,P-triphenyl-phospha-λ⁵-azene (2.4 mmol) and ethoxyacetylene (40% in n-hexane, 4 ml) was added and the solutions heated at 120 °C for 45 min with slow stirring. All volatile components were removed in vacuo (ca. 0.01 mbar) and the products separated by low-temperature column chromatography (SiO₂, –10 °C, 10 × 2 cm, n-pentane/diethyl ether 2:1). Evaporation of the third fractions yielded complexes 7a,b as brown oils.

2.1.1 Complex 7a

Yield: 800 mg, (85.9%); ¹H NMR (CDCl₃) δ 4.68 (dd, ²J_HH = 2.4 Hz, ³J_PH = 6.1 Hz, 1H, =CH₂), 5.02 (dd, ²J_HH = 2.7 Hz, ³J_PH = 22.8 Hz, 1H, =CH₂), 7.00 (m_c, 5H, Ph), 7.25 (m_c, 10H, Ph), 7.58 (m_c, 5H, Ph); ¹³C{¹H} NMR (CDCl₃) δ 96.5 (d, ²J_PC = 18.5 Hz, =CH₂), 126.3 (d, ¹J_PC = 102.6 Hz, ipso-Ph₃P), 127.8 (d, ⁴J_PC = 3.2 Hz, para-Ph), 128.1 (d, ³J_PC = 12.1 Hz, meta-Ph), 128.2 (d, ²J_PC = 9.8 Hz, ortho-Ph), 128.8 (d, ¹J_PC = 61.4 Hz, ipso-Ph), 128.7 (d, ³J_PC = 12.6 Hz, meta-Ph₃P), 132.7 (d, ⁴J_PC = 2.7 Hz, para-Ph₃P), 133.2 (d, ²J_PC = 10.1 Hz, ortho-Ph₃P), 161.5 (dd, ¹J_PC = 20.1 Hz, ⁴J_PC = 3.0 Hz, PCO), 164.6 (dd, ²J_PC = 12.4 Hz, ²J_PC = 6.0 Hz, PNC), 196.2 (d, ²J_PC = 8.0 Hz, ¹J_WC = 126.0 Hz, cis-CO), 200.0 (d, ²J_PC = 23.7 Hz, trans-CO); ³¹P{¹H} NMR (CDCl₃) δ 24.6 (s, PPh₃), 69.0 (s, ¹J_WP = 266.6 Hz); UV/vis (CH₃CN) λ (log ε) = 228 (4.85), 250 (4.51), 262 (4.33), 270 (4.18), 282 (3.88); IR (KBr) $\overset{\tilde{}}{v}$ 2047 (s, CO), 2011 (s, CO), 1947 (vs, CO), 1921 (vs, CO) cm^–1; MS (pos.-DCI(NH₃) ; ³⁵Cl, ¹⁸⁴W): m/z (%) = 776 (60) [M]⁺ ; MS (neg.-DCI(NH₃), ³⁵Cl, ¹⁸⁴W); m/z (%) = 776 (18) [M]^–•, 748 (32) [M–CO]^–•, 324 (100) [W(CO)₅]^–•.

2.1.2 Complex 7b

240 mg, (50.0%); ¹H NMR (CDCl₃) δ 1.16 (t, ³J_HH = 7.1 Hz, 3H, CO₂CH₂CH₃), 1.74 (m_c, 2H, CH₂CH₂CO₂CH₂CH₃), 2.14 (m_c, 2H, CH₂CH₂CO₂CH₂CH₃), 3.99 (q, ³J_HH = 7.1 Hz, 2H, CO₂CH₂CH₃), 4.63 (dd, ²J_HH = 2.7 Hz, ³J_PH = 6.4 Hz, 1H, =CH₂), 5.22 (dd, ²J_HH = 2.7 Hz, ³J_PH = 22.3 Hz, 1H, =CH₂), 7.40 (m_c, 5H, Ph), 7.51 (m_c, 3H, Ph), 7.73 (m_c, 7H, Ph); ¹³C{¹H} NMR (CDCl₃) δ 15.2 (s, CH₂CH₃), 29.1 (d, ²J_PC = 3.7 Hz, CH₂CH₂CO₂CH₂CH₃), 37.2 (d, ¹J_PC = 18.1 Hz, –CH₂CH₂CO₂CH₂CH₃), 61.8 (s, OCH₂CH₃), 97.5 (d, ²J_PC = 17.1 Hz, =CH₂), 127.3 (d, ¹J_PC = 102.7 Hz, ipso-Ph), 129.7 (d, ³J_PC = 12.7 Hz, meta-Ph), 133.8 (d, ⁴J_PC = 2.8 Hz, para-Ph), 134.2 (d, ²J_PC = 10.1 Hz, ortho-Ph), 160.4 (dd, ¹J_PC = 19.2 Hz, ⁴J_PC = 2.9 Hz, PCO), 165.1 (dd, ²J_PC = 12.4 Hz, ²J_PC = 5.8 Hz, PNC), 173.1 (d, ³J_PC = 13.7 Hz, CO₂CH₂CH₃), 197.1 (d, ²J_PC = 8.0 Hz, ¹J_WC = 125.6 Hz, cis-CO), 200.9 (d, ²J_PC = 23.5 Hz, trans-CO); ³¹P{¹H} NMR (CDCl₃) δ 23.6 (s, PPh₃), 72.0 (s, ¹J_WP = 264.0 Hz, ²J_PH = 20.9 Hz); MS (EI, 70 eV, ¹⁸⁴W); m/z (%) = 774 (5) [M–CO]^+•, 746 (17) [M–2CO]^+•, 261 (100) [PPh₃–H]⁺.

3 Supplementary Material

The supplementary material has been sent to the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK/Fachinformationzentrum Karlsruhe, Abt. PROKA, 76344 Eggenstein-Leopoldshafen, Germany, as supplementary material CCDC 212951 and can be obtained by contacting the CCDC/FIZ (quoting the article details and the corresponding SUP number).

Bibliographie

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[2] J. Nieuwenhuis; J.F. Arens; J.J. Van Daalen; A. Kraak; J.F. Arens; B. Rosebeek; J.F. Arens Recl. Trav. Chim. Pays-Bas, 77 (1958), p. 761

[3] R.A. Ruden J. Org. Chem., 39 (1974), p. 3607

[4] N.H. Tran Huy; F. Mathey Phosphorus Sulfur Silicon, 47 (1990), p. 477

[5] R. Streubel Coord. Chem. Rev., 227 (2002), p. 172

[6] R. Streubel; N. Hoffmann; H.-M. Schiebel; F. Ruthe; P.G. Jones Eur. J. Inorg. Chem., 957 (2002)

[7] A. Schmidpeter (F. Mathey, ed.), Phosphorus–Carbon Heterocyclic Chemistry: The Rise of a New Domain, Pergamon, Oxford, 2001, p. 363

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