Deca-B-fluorination of Diammonioboranes. Structures and NMR Characterization of 1,2-, 1,7-, and 1,12-B12H10(NH3)2 and 1,2-, 1,7-, and 1,12-B12F10(NH3)2

5 years ago

Deca-B-fluorination of Diammonioboranes. Structures and NMR Characterization of 1,2-, 1,7-, and 1,12-B12H10(NH3)2 and 1,2-, 1,7-, and 1,12-B12F10(NH3)2

Multiple variations of the reaction conditions reported in 1964 for the diamination of K2B12H12 (potassium dodecahydro-closo-dodecaborate(2−)) with hydroxylamine-O-sulfonic acid were studied to improve the isolated yields of the three isomers of B12H10(NH3)2. Screening the sets of reaction conditions without completely working up each of the reaction mixtures, and therefore without the lengthy separation and isolation of the individual B12H10(NH3)2 isomers for each reaction mixture, was possible by recording ¹H-¹⁵N HSQC NMR spectra of the crude reaction mixtures. The ¹H-dimension of these spectra exhibited narrow, baseline separated resonances for 1,2-, 1,7- and 1.12-B12H10(NH3)2 and for the B12H11(NH3)⁻ intermediate, allowing their relative concentrations to be determined to the nearest percent. The best synthetic conditions resulted in 9, 25, and 6% isolated yields of 1,2-, 1,7- and 1.12-B12H10(NH3)2, respectively. The decafluoro derivatives 1,2-, 1,7-, and 1,12-B12F10(NH3)2 were prepared for the first time by direct fluorination of the B12H10(NH3)2 isomers, either individually or as a mixture subsequently separated by column chromatography similar to the separation and purification of the B12H10(NH3)2 isomers. The structures of 1,7-B12F10(NH2)2∙4CH3CONH2, 1,12-B12F10(NH2)2∙6CH3CONH2, 1,2-B12H10(NH2)2∙1.5CH3CO2CH2CH3, 1,7-B12H10(NH2)2∙1.23H2O, 1,12-B12H10(NH2)2∙2CH3CN, and solvent-free 1,12-B12H10(NH2)2 were determined by single-crystal X-ray diffraction.

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DOI: S002211391730564X