Yam Mandy, Chong Jonathan H, Tsang Chi-Wing, Patrick Brian O, Lam Anita E, Gates Derek P
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1.
Inorg Chem. 2006 Jun 26;45(13):5225-34. doi: 10.1021/ic060236p.
Phosphaalkenes (MesP=CRR': R = R' = Ph (1a); R = R' = 4-FC6H4 (1b); R = Ph, R' = 4-FC6H4 (1c); R = R' = 4-OMeC6H4 (1d); R = Ph, R' = 4-OMeC6H4 (1e); R = Ph, R' = 2-pyridyl (1f)) are prepared from the reaction of MesP(SiMe3)2 and O=CRR' in the presence of a trace of KOH or NaOH. The base-catalyzed phospha-Peterson reaction is quantitated by NMR spectroscopy, and isolated yields of phosphaalkene between 40 and 70% are obtained after vacuum distillation and/or recrystallization. The asymmetrically substituted phosphaalkenes (1c, 1e, 1f) form as 1:1 mixtures of E and Z isomers; however, X-ray crystallography reveals that the E isomers crystallize preferentially. Interestingly, E-1e and E-1f readily isomerize in solution in the dark, although the rate of isomerization is much faster when samples are exposed to light. X-ray crystal structures of 1b, E-1e, and E-1f reveal that the P=C bond lengths (average of 1.70 A) are in the long end of the range typically found in phosphaalkenes (1.61-1.71 A). Attempts to prepare isolable P-adamantyl phosphaalkenes following this route were unsuccessful. Although AdP=CPh2 (2a) is detected by 31P NMR spectroscopy, attempts to isolate this species afforded the 1,2-diphosphetane (AdPCPh2)2 (3a), which was characterized by X-ray crystallography.
磷烯（MesP=CRR'：R = R' = 苯基（1a）；R = R' = 4-氟苯基（1b）；R = 苯基，R' = 4-氟苯基（1c）；R = R' = 4-甲氧基苯基（1d）；R = 苯基，R' = 4-甲氧基苯基（1e）；R = 苯基，R' = 2-吡啶基（1f））由MesP(SiMe3)2与O=CRR'在痕量KOH或NaOH存在下反应制备。碱催化的磷-Peterson反应通过核磁共振光谱进行定量分析，经真空蒸馏和/或重结晶后，磷烯的分离产率为40%至70%。不对称取代的磷烯（1c、1e、1f）以E和Z异构体的1:1混合物形式形成；然而，X射线晶体学表明E异构体优先结晶。有趣的是，E-1e和E-1f在黑暗中在溶液中容易异构化，尽管当样品暴露于光时异构化速率要快得多。1b、E-1e和E-1f的X射线晶体结构表明，P=C键长（平均为1.70 Å）处于磷烯中通常发现的范围（1.61 - 1.71 Å）的较长一端。尝试通过此路线制备可分离的P-金刚烷基磷烯未成功。尽管通过31P核磁共振光谱检测到了AdP=CPh2（2a），但尝试分离该物种得到了1,2-二磷杂环丁烷（AdPCPh2）2（3a），其通过X射线晶体学进行了表征。
