1,3-Diphospholene-4-ylidene chromium (tungsten) pentacarbonyl complexes formed by CO insertion into the ring of a 1,3-diphosphacyclobutane-2,4-diyl-2-ide - Complexes of a phosphanyl carbene or a phosphonium ylide?

André Fuchs, Dietrich Gudat, Martin Nieger, Olaf Schmidt, Manuel Sebastian, L. Nyulászi, Edgar Niecke

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Reaction of the 1,3-diphosphacyclobutane-2,4-diyl-2-ide 1 with chromium or tungsten hexacarbonyl afforded the anionic complexes [cyclo-{P((Mes*)-C(SiMe3)-P (Mes*)-C(O)-C[M(CO)5]}]-(3ab: M = Cr, W) by the formal insertion of CO into the four membered ring. Computational analysis suggests that this reaction proceeds via two intermediates that can be formulated as a cyclic metal acyl and an acyclic ketenyl complex. The anionic complexes 3a,b further reacted with electrophiles to afford the neutral complexes [cyclo-[P(Mes*)-C(SiMe3)-P(Mes*)-C(OR)-C[M(CO)5]}] (4a,b: M = Cr, W, R = Me; 5, 6: M = Cr, R = SiMe3, H). All products were characterized by standard spectroscopic (NMR and MS) techniques, and 4a,b further by extensive oneand two-dimensional multinuclear (1H, 13C, 31P, 183W) NMR studies. From these investigations, an unequivocal assignment of chemical shifts and coupling constants was derived, confirming unusually large shielding for the formal carbenic carbon atoms which exceed even those in complexes of imidazoyl carbenes. Single-crystal X-ray diffraction analyses of 3a, 4a,b, and 5 revealed that all of these compounds contain planar P2C3 rings. The phosphorus atoms are slightly pyramidal, and the carbon-metal distances (C - Cr 218 pm, C - W 230 pm) suggest low bond orders. Comparison of the structural parameters of 3a with those of the O-substitution products 4a, 5 revealed substantial changes in endocyclic P - C bond lengths and the degree of pyramidal character of bonding at the phosphorus atoms. In line with the spectroscopic and computational results, these effects were interpreted in terms of a considerable reorganization of π electrons in the ring, which induces a substantial degree of aromatic character in the neutral complexes 4-6.

Original languageEnglish
Pages (from-to)2188-2196
Number of pages9
JournalChemistry - A European Journal
Volume8
Issue number9
DOIs
Publication statusPublished - May 3 2002

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Tungsten
Chromium
Carbon Monoxide
Atoms
Phosphorus
Carbon
Metals
Nuclear magnetic resonance
Chemical shift
Bond length
Shielding
Substitution reactions
Single crystals
X ray diffraction
Electrons
carbene

Keywords

  • Carbene complexes
  • Computer chemistry
  • Insertion
  • NMR spectroscopy
  • Phosphorus heterocycles

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

1,3-Diphospholene-4-ylidene chromium (tungsten) pentacarbonyl complexes formed by CO insertion into the ring of a 1,3-diphosphacyclobutane-2,4-diyl-2-ide - Complexes of a phosphanyl carbene or a phosphonium ylide? / Fuchs, André; Gudat, Dietrich; Nieger, Martin; Schmidt, Olaf; Sebastian, Manuel; Nyulászi, L.; Niecke, Edgar.

In: Chemistry - A European Journal, Vol. 8, No. 9, 03.05.2002, p. 2188-2196.

Research output: Contribution to journalArticle

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