Borane Cluster Photochemistry. 3. The Photochemistry and Organometallic Rearrangement Chemistry of σ-Metalated Small Borane Cluster Compounds

Bruce H. Goodreau, Lianna R. Orlando, James T. Spencer

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

The photochemistry of a-metalated pentaborane(9) complexes [2-(Fe(η5-C5H5)(CO)2)B5H8] (1) and [2,4-(Fe(η5-C5H5)(CO)2)2B5H7] (2) is described. These compounds readily undergo a clean photoinduced decarbonylation reaction to lose a carbon monoxide ligand upon irradiation to generate an unsaturated, 16-electron iron intermediate. The isolated products arise from the insertion of the reactive 16-electron iron center into the basal plane of the borane cluster. Thus, the conversion of the square-pyramidal B5 cluster complexes, 1 and 2, into the pentagonal-pyramidal FeB5 vertex complexes, 2-(η5-C5H5)-2-(CO)-2-FeB5H8 (3) and 4-(Fe(η5-C5H5)(CO)2)-2-(η5-C5H5)-2-(CO)-2-FeB5H7 (4), respectively, was observed. The complete characterization of the products by 1H,11B NMR (including both 1D and 2D 11B–11B {1H} COSY data), infrared, and mass spectral analyses are reported. The X-ray crystal structure of 3 is also reported. Upon extended UV irradiation of either complex 2 or 4, the only products observed were the dimeric [Fe(η5-C5H5)CO)2]2 complex and complex 3, which apparently arise from the light-induced fission of a terminal σ iron-cage bond. The formation of the dimeric [Fe(η5-C5H5)(CO)2)2 complex in this photolysis was expected through a radical coupling process of the initially photogenerated [Fe(η5-C5H5)(CO)2]2 species. The other anticipated coupling product, [(Fe(η5-C5H5)(CO))B5H7]2, was not found, but rather the formation of complex 3 was observed, which presumably formed through the extraction a hydrogen atom by the intermediate radical [2-(Fe(η5-C5H5)(CO))B5H7]2 complex. A unique rearrangement of complex 4 to a new isomer, [3-(Fe(η5-C5H5)(CO)2)-2-(η5-C5H5)-2-(CO)-2-FeB5H7] (5) is also reported. Crystallographic data for 3: space group Pnma (No. 62, orthorhombic), a = 14.889(1) Å, b = 9.4560(9) Å, c = 7.2838(9) Å, V = 1025.5(3) Å3, Z = 4 molecules/cell, Rw = 0.037 for 959 independent reflections.

Original languageEnglish (US)
Pages (from-to)11754-11761
Number of pages8
JournalJournal of the American Chemical Society
Volume117
Issue number47
DOIs
StatePublished - Jan 1 1995

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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