... mmol) of 4a which was heated at 450°C for 6 h in an evacuated, sealed pyrex tube of 20 ml volume showed, as ... Ber. 1992, 125, 2343 - 2346 ... The undissolved orange powder was filtrated off and dried in vacuo (yield 0.15 g). - Elementary analysis: Found B 4.56, Br 41.46, P 46.79 ...