Mechanism of ketone and alcohol formations from alkenes and alkynes on the head-to-head 2-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex.
Mechanism of ketone and alcohol formations from alkenes and alkynes on the head-to-head 2-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex.
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头对头 2-吡啶酮桥接顺式二氨铂 (III) 双核配合物上的烯烃和炔烃形成酮和醇的机制。
DOI：
10.1021/ja020953s
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发表时间：
2003
影响因子：
15
通讯作者：
Kazuko Matsumoto
中科院分区：
文献类型：
--
作者：
N. Saeki;Noriko Nakamura;T. Ishibashi;Moritatsu Arime;Hideo Sekiya;K. Ishihara;Kazuko Matsumoto
研究了具有不等价的两个铂原子Pt（N（2）O（2））和Pt（N（4））的2-吡啶酮桥联的顺式二氨合铂（III）双核配合物与对苯乙烯磺酸盐、2-甲基-2-丙烯-1-磺酸盐、4-戊烯-1-醇和4-戊炔-1-醇的反应动力学。在Pt（III）双核配合物的浓度远小于烯烃的浓度的准一级反应条件下，观察到了一个基本上连续的四步反应：在第一步（步骤1）中，烯烃优先与Pt（N（2）O（2））π配位，然后是另一个烯烃分子与Pt（N（4））π配位（步骤2）。在下一步（步骤3）中，水对配位烯烃的亲核攻击引发Pt（N（2）O（2））上的π-sigma键转化，并释放Pt（N（4））上的第二个π键合烯烃分子。最后，Pt（N（2）O（2））上的烷基发生还原消除以产生烷基化合物（步骤4）。第一次水被烯烃取代（步骤1）发生在配合物的二水合和水合氢氧化物形式上，而第二次取代（步骤2）除了常见的H（2）O取代（路径c）之外，还在Pt（N（4））上的配位OH（-）（路径a）或Pt（N（4））的配位不饱和五配位中间体（路径B）上进行。对苯乙烯磺酸盐和2-甲基-2-丙烯-1-磺酸盐的反应通过路径B和c进行，而4-戊烯-1-醇和4-戊炔-1-醇的反应通过路径a和c进行。这种差异反映了π配位烯烃对Pt（N（2）O（2））的反式效应和/或反式影响的差异。路径B中的五配位态仅被磺基烯烃所采用，因为这些烯烃具有更强的反式效应。步骤3和4反映了轴向烷基配体（R）对电荷局域化（R-Pt（IV）（N（2）O（2））-Pt（II）（N（4）和离域化的影响（R-Pt（III）（N（2）O（2））-Pt（III）（N（4））-OH（2））;当R是具有吸电子基团的对苯乙烯磺酸酯时，二聚体中的电荷局部化不太明显，Pt（N（4））原子上的水分子保留在中间态（R-Pt（III）（N（2）O（2））-Pt（III）（N（4））-OH（2））。在这两种途径中，烷基基团经历水的亲核攻击，并且氧化产物通过还原消除释放。
Reactions of the head-to-head 2-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex having nonequivalent two platinum atoms, Pt(N(2)O(2)) and Pt(N(4)), with p-styrenesulfonate, 2-methyl-2-propene-1-sulfonate, 4-penten-1-ol, and 4-pentyn-1-ol were studied kinetically. Under the pseudo first-order reaction conditions that the concentration of the Pt(III) dinuclear complex is much smaller than that of olefin, a consecutive basically four-step reaction was observed: the olefin pi-coordinates preferentially to the Pt(N(2)O(2)) in the first step (step 1), followed by the second pi-coordination of another olefin molecule to the Pt(N(4)) (step 2). In the next step (step 3), the nucleophilic attack of water to the coordinated olefin triggers the pi-sigma bond conversion on the Pt(N(2)O(2)), and the second pi-bonding olefin molecule on the Pt(N(4)) is released. Finally, reductive elimination occurs to the alkyl group on the Pt(N(2)O(2)) to produce the alkyl compound (step 4). The first water substitution with olefin (step 1) occurs to the diaqua and aquahydroxo forms of the complex, whereas the second substitution (step 2) proceeds either on the coordinated OH(-) on the Pt(N(4)) (path a) or on the coordinatively unsaturated five-coordinate intermediate of the Pt(N(4)) (path b), in addition to the common substitution of H(2)O (path c). The reactions of p-styrenesulfonate and 2-methyl-2-propene-1-sulfonate proceed through paths b and c, whereas the reactions of 4-penten-1-ol and 4-pentyn-1-ol proceed through paths a and c. This difference reflects the difference of the trans effect and/or trans influence of the pi-coordinated olefins on the Pt(N(2)O(2)). The pentacoordinate state in path b is employed only by the sulfo-olefins, because these exert stronger trans effect. The steps 3 and 4 reflect the effect of the axial alkyl ligand (R) on the charge localization (R-Pt(IV)(N(2)O(2))-Pt(II)(N(4))) and delocalization (R-Pt(III)(N(2)O(2))-Pt(III)(N(4))-OH(2)); when R is p-styrenesulfonate having an electron withdrawing group, the charge localization in the dimer is less pronounced and the water molecule on the Pt(N(4)) atom is retained (R-Pt(III)(N(2)O(2))-Pt(III)(N(4))-OH(2)) in the intermediate state. In both routes, the alkyl group undergoes nucleophilic attack of water, and the oxidized products are released via reductive elimination.