Reaction of tertiary phosphine selenides, R3PSe (R = Me2N, Et2N or C6H11), with dibromine. The first reported examples of 1∶1 addition
作者:Stephen M. Godfrey、Sheena L. Jackson、Charles A. McAuliffe、Robin G. Pritchard
DOI:10.1039/a807892k
日期:——
The R3PSeBr2 compounds (R = Me2N, Et2N or C6H11) have been prepared and characterised by 31P-H} and infrared spectroscopy. The compounds R3PSeBr2 (R = Me2N or C6H11) have also been crystallographically characterised. In contrast to the analogous diiodo compounds R3PSeI2 (which have a molecular Ψ-tetrahedral charge-transfer structure, R3PSeIâI), the R3PSeBr2 compounds adopt Ψ-trigonal bipyramids at the selenium centre (taking account of the stereochemically active lone pairs). The crystal structure of (Me2N)3PSeBr2 exhibits very different d(SeâBr), 2.602(2) and 2.544(2) Ã
. This phenomenon is reasoned to be due to the fact that both staggered and eclipsed SeâBr bonds are observed in the structure. The crystal structure of (C6H11)3PSeBr2 shows two crystallographically independent molecules in the asymmetric unit, d(SeâBr) being identical in one molecule, 2.568(3) and 2.566(3) Ã
, but significantly different in the second molecule, 2.591(3) and 2.556(3) Ã
. A possible explanation for this is the presence of a close non-bonded Br· · ·Br contact in this second (C6H11)3PSeBr2 molecule. The compounds R3PSeBr2 (R = Me2N or C6H11) both exhibit PâSe bonds typical of those expected for single bonds, 2.262(2) and 2.263(2) average, respectively, again in contrast to the analogous diiodo compounds, R3PSeI2, in which significant PâSe double bond character was retained. The 31P-H} NMR and infrared spectroscopic data for R3PSeBr2 (R = Me2N, Et2N or C6H11) are discussed with respect to those of the parent tertiary phosphine selenide, R3PSe.
R3PSeBr2化合物(R = Me2N、Et2N或C6H11)已通过31P-H}和红外光谱法制备并表征。R3PSeBr2化合物(R = Me2N或C6H11)也通过晶体学进行了表征。与类似的二碘化合物R3PSeI2(具有分子Ψ-四面体电荷转移结构,R3PSeI−I)不同,R3PSeBr2化合物在硒中心采用Ψ-三角双锥构型(考虑到空间活性孤对电子)。(Me2N)3PSeBr2的晶体结构显示出非常不同的d(Se−Br),分别为2.602(2)和2.544(2) Å。这一现象被认为是由于结构中同时观察到交错和重叠的Se−Br键。(C6H11)3PSeBr2的晶体结构显示不对称单元中存在两种晶体学独立的分子,d(Se−Br)在一种分子中相同,分别为2.568(3)和2.566(3) Å,而在第二种分子中显著不同,分别为2.591(3)和2.556(3) Å。对此的一种可能解释是在第二种(C6H11)3PSeBr2分子中存在接近的非成键Br···Br接触。R3PSeBr2化合物(R = Me2N或C6H11)均显示出预期为单键的典型P−Se键,平均值分别为2.262(2)和2.263(2) Å,再次与类似的二碘化合物R3PSeI2形成对比,后者保留了显著的P−Se双键特性。R3PSeBr2(R = Me2N、Et2N或C6H11)的31P-H} NMR和红外光谱数据与母体三烷基膦硒化物R3PSe的数据进行了讨论。