Reactions of P4 and I2 with Ag[Al(OC(CF3)3)4]: from elusive polyphosphorus cations to subvalent P3I6+ and phosphorus rich P5I2+
作者:Ingo Krossing
DOI:10.1039/b103957c
日期:——
Reactions of X2 (X = Br, I), P4 and Ag(CH2Cl2)[Al(OR)4] [R = C(CF3)3] in suitable ratios to prepare naked polyphosphorus cations were carried out and led to products which suggested the presence of these elusive cations as intermediates. At temperatures above −30 °C to rt the initially formed cations decomposed the Al(OR)4− anion giving, in two cases, the more stable fluoride bridged (RO)3Al–F–Al(OR)3− anion. When Br2 was used as the oxidising agent the proposed intermediate phosphorus cation (P5+?) reacted with the solvent CDCl3 by double insertion of a P+ unit into the C–Cl bond giving Cl2P(CDCl2)2[(RO)3Al–F–Al(OR)3], 1.
When I2 was used as the oxidiser the reaction led to the marginally stable P3I6[(RO)3Al–F–Al(OR)3], 2 (X-ray). By using very mild conditions throughout (−80 °C) the primary product of the reaction of Ag(P4)2[Al(OR)4] and I2 was isolated: P5I2[Al(OR)4], 3, containing the P5I2+ cation with a hitherto unknown C2v-symmetric P5 cage as structural building block. P3I6[Al(OR)4], 4, was directly synthesised in quantitative yield starting from P2I4, PI3 and Ag(CH2Cl2)[Al(OR)4] in CH2Cl2 solution. P3I6+
is formed through the P2I5+ stage (31P-NMR). P3I6+ (av.: P2.33) is the first subvalent P–X cation (X = H, F, Cl, Br, I). P5I2+ (av.: P0.6) is the first phosphorus rich binary P–X cation. They are the third and fourth example of a binary P–X cation after the known PX4+ and P2X5+ cations. The observed reactions were fully accounted for by thermochemical Born–Haber cycles based on (RI-)MP2/TZVPP ab initio, COSMO solvation and lattice enthalpy calculations (all phases). The gaseous enthalpies of formation of several species were calculated to be (in kJ mol−1): P5+ (913), P3I6+ (694), P5I2+ (792), P2I5+
(733), Ag(P4)2+ (784).
在适当比例下进行X2(X = Br,I)、P4和Ag(CH2Cl2)[Al(OR)4](R = C(CF3)3)的反应,制备裸露的聚磷阳离子,生成的产物表明这些难以捉摸的阳离子作为中间体存在。在高于-30°C至室温的温度下,最初形成的阳离子分解Al(OR)4-阴离子,其中两种情况下产生了更稳定的氟化物桥接的(RO)3Al-F-Al(OR)3-阴离子。当使用Br2作为氧化剂时,提出的中间磷阳离子(P5+?)通过磷阳单元对C-Cl键的双插入反应与溶剂CDCl3反应,生成Cl2P(CDCl2)2[(RO)3Al-F-Al(OR)3],1。当使用I2作为氧化剂时,反应导致生成略微稳定的P3I6[(RO)3Al-F-Al(OR)3],2(X射线)。通过在整个过程中使用非常温和的条件(-80°C),可以分离出Ag(P4)2[Al(OR)4]和I2反应的主要产物:P5I2[Al(OR)4],3,其中含有迄今未知的C2v对称P5笼作为结构构建单元的P5I2+阳离子。直接从P2I4、PI3和Ag(CH2Cl2)[Al(OR)4]在CH2Cl2溶液中合成了产率定量的P3I6[Al(OR)4],4。P3I6+通过P2I5+阶段(31P-NMR)形成。P3I6+(平均值:P2.33)是第一个次价P-X阳离子(X = H,F,Cl,Br,I)。P5I2+(平均值:P0.6)是第一个富磷的二元P-X阳离子。它们是继已知的PX4+和P2X5+阳离子之后的第三个和第四个二元P-X阳离子。观察到的反应完全可以通过基于(RI-)MP2/TZVPP从头算、COSMO溶剂化和晶格焓计算(所有相)的热化学Born-Haber循环来解释。计算了几个物种的气相生成焓(kJ mol-1):P5+(913),P3I6+(694),P5I2+(792),P2I5+(733),Ag(P4)2+(784)。