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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Pseudo-rotation mechanism for fast olefin exchange and substitution processes at orthometalated C,N-complexes of platinum(II)
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Pseudo-rotation mechanism for fast olefin exchange and substitution processes at orthometalated C,N-complexes of platinum(II)

机译：在铂金属的正金属化C，N-络合物上快速烯烃交换和取代过程的伪旋转机理

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摘要

Bridge splitting in chloroform of the orthometalated chloro-bridged complex[Pt(mu-Cl)(2-ME_2NCH_2C_6H_4)]_2(1),with ethene,cyclooctene,allyl alcohol and phosphine according to 1 + 2L-> 2[PtCl(2-ME_2NCH_2C_6H_4)(L)],where L = C_2H_4(3a),C_8H_(14),(3b),CH_2CHCH_2OH(3c),and PPH_3(4a and 4b)gives monomeric species with L coordinated trans or cis to aryl.With olefms the thermodynamically stable isomer with L coordinated cis to aryl is formed directly without an observable intermediate.With phosphine and pyridine,the kinetically controlled trans-product isomerizes slowly to the more stable cis-isomer.Bridge splitting by olefms is slow and first-order in 1 and L,with largely negative DELTAS~#.Substitution of ethene cis to aryl by cyclooctene and allyl alcohol to form 3b and 3c,and substitution of cot from 3b by allyl alcohol to form 3c are first order in olefin and complex,ca.six orders of magnitude faster than bridge cleavage due to a large decrease in DELTAH~#,and with largely negative AS}.Cyclooctene exchange at 3b is first-order with respect to free cyclooctene and platinum complex.All experimental data for olefin substitution and exchange are compatible with a concerted substitution/isomerization process via a turnstile twist pseudo-rotation in a short-lived labile five-coordinated intermediate,involving initial attack on the labile coordination position trans to the sigma-bonded aryl.Bridge-cleavage reactions of the analogous bridged complexes occur similarly,but are much slower because of their ground-state stabilization and steric hindrance.
机译：根据1 + 2L-> 2 [PtCl（2） -ME_2NCH_2C_6H_4）（L）]，其中L = C_2H_4（3a），C_8H_（14），（3b），CH_2CHCH_2OH（3c）和PPH_3（4a和4b）提供具有L的反式或顺式与芳基配位的单体。烯烃直接形成具有L配位的顺式与芳基的热力学稳定的异构体，而没有可观察到的中间体。通过膦和吡啶，动力学控制的反式异构体缓慢地异构化为更稳定的顺式异构体。烯烃的桥拆分很慢且是一阶的在1和L中，DELTAS〜＃在很大程度上为负。在烯烃和配合物中，乙烯被环辛烯和烯丙醇取代成顺式芳基以形成3b和3c，而烯丙醇将3b的cot被烯丙醇取代形成3c是一阶的。由于DELTAH_＃的大幅下降，并且AS值基本上为负，因此比桥式劈裂快六个数量级。在3b处的环辛烯交换相对于游离的环辛烯和铂络合物是一阶的。所有烯烃取代和交换的实验数据都通过短寿命不稳定五配位的旋转栅假旋转进行协调的取代/异构化过程。中间体，其对不稳定配位的初始攻击转移至sigma键合的芳基上。类似的桥联配合物的桥裂解反应同样发生，但由于其基态稳定和位阻，其反应要慢得多。

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