Krzysztof Owsianik, R. Chauvin, A. Balińska
Aug 12, 2009
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Journal
Organometallics
Abstract
Treatment of 1,8-bis(diphenylphosphino)naphthalene (1) with borane−dimethyl sulfide complex in THF/Et2O solution affords monoborane adduct 3 irrespective of the molar ratio of the reagents. The monoboronation product has been characterized by multinuclear (1H, 31P, 13C, 11B) NMR spectroscopy and MS-FAB measurements. Optimization of its structure with DFT methods at the B3LYP/6-31+G(d) level of theory revealed that steric hindrance around the diphenylphosphino group prevents formation of the bis-borane adduct. In dichloromethane or chloroform solution boronation of bis-phosphine 1 with H3B·Me2S results in the unexpected formation of a cyclic dihydroboronium chloride, 4·Cl. The corresponding cyclic iodide 4·I and triflate 4·TfO are formed by treatment of bis-phosphine 1 with H3B·Me2S followed by methyl iodide and methyl triflate, respectively, in THF/Et2O solution. The hexafluorophosphate 4·PF6 prepared by anion exchange from the chloride 4·Cl has also been characterized by single-crystal X-ray diffraction....