Chinen Beatrice L, Hyvl Jakub, Brayton Daniel F, Riek Matthew M, Yoshida Wesley Y, Chapp Timothy W, Rheingold Arnold L, Cain Matthew F
Department of Chemistry, University of Hawai'i at Mānoa 2545 McCarthy Mall Honolulu HI 96822 USA
Department of Chemistry, Allegheny College 520 N. Main Street Meadville PA 16335 USA.
RSC Adv. 2021 Aug 25;11(46):28602-28613. doi: 10.1039/d1ra05926b. eCollection 2021 Aug 23.
In order to stabilize a 10-P-3 species with symmetry and two lone pairs on the central phosphorus atom, a specialized ligand is required. Using an NCN pincer, previous efforts to enforce this planarized geometry at P resulted in the formation of a -symmetric, 10π-electron benzazaphosphole that existed as a dynamic "bell-clapper" in solution. Here, OCO pincers 1 and 2 were synthesized, operating under the hypothesis that the more electron-withdrawing oxygen donors would better stabilize the 3-center, 4-electron O-P-O bond of the 10-P-3 target and the sp-hybridized benzylic carbon atoms would prevent the formation of aromatic P-heterocycles. However, subjecting 1 to a metalation/phosphination/reduction sequence afforded cyclotriphosphane 3, resulting from trimerization of the P(i) center unbound by its oxygen donors. Pincer 2 featuring four benzylic CF groups was expected to strengthen the O-P-O bond of the target, but after metal-halogen exchange and quenching with PCl, unexpected cyclization with loss of CHCl was observed to give monochlorinated 5. Treatment of 5 with (-CH)CHMgBr generated crystalline P-(-Tol) derivative 6, which was characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. The complex F NMR spectra of 5 and 6 observed experimentally, were reproduced by simulations with MestreNova.
为了稳定具有 对称性且中心磷原子上有两个孤对电子的10 - P - 3物种，需要一种特殊的配体。使用NCN钳形配体时，之前在磷原子处强制形成这种平面化几何结构的努力导致形成了一种 - 对称的10π电子苯并氮磷杂茂，它在溶液中以动态的“钟摆”形式存在。在此，合成了OCO钳形配体1和2，其依据的假设是，吸电子能力更强的氧供体将更好地稳定10 - P - 3目标的3中心4电子O - P - O键，且sp杂化的苄基碳原子将阻止芳香族P - 杂环的形成。然而，使1经历金属化/膦化/还原序列得到了环三膦烷3，这是由未被其氧供体束缚的P(i)中心三聚化产生的。具有四个苄基CF基团的钳形配体2预计会增强目标的O - P - O键，但在金属 - 卤素交换并用PCl淬灭后，观察到意外的环化反应并伴有CHCl的损失，得到了单氯化产物5。用(-CH)CHMgBr处理5生成了结晶性的P - (-Tol)衍生物6，通过核磁共振光谱、元素分析和X射线晶体学对其进行了表征。通过MestreNova模拟重现了实验观察到的5和6的复杂氟核磁共振谱。
