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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Exploration of isomeric bis(phosphanyl)-substituted carbenium ions:identification and synthesis of the most stable isomer
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Exploration of isomeric bis(phosphanyl)-substituted carbenium ions:identification and synthesis of the most stable isomer

机译：异构化双（膦烷基）取代的碳正离子的探索：最稳定异构体的鉴定和合成

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Isomeric bis(phosphanyl) carbenium ions have been investigated by theoretical [MP2/6-31G(d,p) level of theory] and experimental means.On the potential energy surface (PES) of phosphorus cations of the formula [P_2CH_5]~+,five stable isomers are found.Their structures follow the stability order (DELTA_(rel)/kcal mol~(-1)):P-protonated diphosphiranium,[(H_2P)(HP)CH_2]~+ la (0.0) > C-phosphonio phosphaalkene,[H_3P-HC=PH]~+ 2a (4.5) bis(phosphanyl) carbenium,[CH(PH_2)_2]~+ 3a (18.5) > C-phosphanyl methylenephosphonium,[H_2P-CH= PH_2]~+ 4a (22.6) diphosphirenium,5a (47.1).The stability order is very different for the family of the four related stable [P_2CH(NH_2)_4]~+ ions Ib,2b,4b,5b in which the phosphorus-bound hydrogens (and one carbon-bound hydrogen in the case of 1b) have been replaced by NH_2 groups:2b (-39.6) 1b (0.0) > 5b (2.2) > =4b (3.7).None of these ions has a structure comparable to the classical amidinium ion [HC(NH_2)]~+.While all amino carbenium ions have a positively charged carbon atom,all phosphorus analogues carry a negative charge on carbon.In some,even the p(pi)-population exceeds unity suggesting that these should be considered as cationic methanides.Experimentally,a derivative of the diphosphiranium ion la could be prepared by methylation of 1,2-bis-(2,4,6-tri-tert-butylphenyl)diphosphirane with MeO_3SCF_3,and this new compound 8 was characterized by NMR methods.Although the most stable member in this family,it could only be observed under stable ion conditions (T < -40 deg C,five-fold excess of MeO_3SCF_3) and decomposes at higher temperatures.
机译：通过理论[MP2 / 6-31G（d，p）的理论水平]和实验手段研究了同构的双（磷烷基）碳正离子。在磷阳离子的势能表面（PES）上，分子式为[P_2CH_5]〜+ ，发现了五个稳定的异构体。它们的结构遵循稳定顺序（DELTA_（rel）/ kcal mol〜（-1））：P-质子化二磷鎓，[（H_2P）（HP）CH_2]〜+ la（0.0）> C -膦酰基磷烯，[H_3P-HC = PH]〜+ 2a（4.5）双（膦酰基）碳鎓，[CH（PH_2）_2]〜+ 3a（18.5）> C-膦酰基亚甲基phosph，[H_2P-CH = PH_2 ]〜+ 4a（22.6）二磷鎓，5a（47.1）。四个相关稳定离子[P_2CH（NH_2）_4]〜+的离子Ib，2b，4b，5b的族的稳定性顺序非常不同。磷结合的氢（在1b情况下为一个碳结合的氢）已被NH_2基团取代：2b（-39.6） 1b（0.0）> 5b（2.2）> = 4b（3.7）离子具有可与传统classical离子[HC（NH_2）]〜+相比的结构。尽管所有氨基碳正离子均具有正离子含磷的碳原子，所有的磷类似物在碳上均带有负电荷。在某些甚至p（pi）人口数超过1的情况下，建议将其视为阳离子甲烷化物。通过实验，可以制备二磷鎓离子la的衍生物通过用MeO_3SCF_3对1,2-双-（2,4,6-三叔丁基苯基）二膦烷进行甲基化，并通过NMR方法对该新化合物8进行了表征。尽管该家族中最稳定的成员只能是在稳定的离子条件下（T <-40摄氏度，MeO_3SCF_3的五倍过量）观察到并在较高温度下分解。

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