REVERSIBLE EXCHANGE OF (ETA-5-CYCLOPENTADIENYL)(DINITROSOALKANE)COBALT COMPLEXES WITH ALKENES - KINETIC AND SPECTROSCOPIC EVIDENCE FOR C5H5CO(NO)2 AS A REACTIVE INTERMEDIATE
REVERSIBLE EXCHANGE OF (ETA-5-CYCLOPENTADIENYL)(DINITROSOALKANE)COBALT COMPLEXES WITH ALKENES - KINETIC AND SPECTROSCOPIC EVIDENCE FOR C5H5CO(NO)2 AS A REACTIVE INTERMEDIATE
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DOI：
10.1021/ja00348a011
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发表时间：
1983-01-01
影响因子：
15
通讯作者：
BERGMAN, RG
中科院分区：
文献类型：
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作者：
BECKER, PN;BERGMAN, RG
将由[CpCoNO] 2 、NO和2，3-二甲基-2-丁烯制备的(α；5-环戊二烯基)(2，3-二甲基-2，3-二亚硝基丁烷)钴(1)与ci'一起加热。 re «do-5, 6-二甲氧基降冰片烯 (2b) 在芳香族溶剂中将其定量转化为 2,3-二甲基-2-丁烯 (4) 和 3b（由 2b 和 [CpCoNO] 2/NO 形成的加合物）。该反应在[1]中为一级反应，在75℃下kobs¿=(4.3±0.3) X 10" 4 s'1，£ a= 29.4±0.4 kcal/mol，A= 1.3 X 1015 s'1。添加烯烃4以线性方式抑制反应，与涉及1可逆解离成2的机制一致， 3-二甲基-2-丁烯和CpCo (NO) 2，然后该二亚硝基与2b反应，如方案I所示。由于配合物5和7分别专门再生(E)-和(Z)-3-甲基-2-戊烯，因此配合物1在2b存在下也发生烯烃交换，其中30= 1.12 X 10" 3。 [CpCoNO] 2 与一氧化氮生成新物质，该新物质在室温下在溶液中稳定。这种材料的反应性太强，无法分离，但可以通过光谱研究其溶液。它在 IR 中显示出两个谱带（1609 和 1690 cm'1），在质子 NMR 中显示出一个共振峰（4.22）；在紫外线中，它在 Xmax 255 nm 处吸收。将烯烃添加到该材料的溶液中可快速生成钴二亚硝基烷烃（方案 III），与烯烃与 [CpCoNO] 2/NO 反应形成的产物相同。根据这些观察结果，该活性物质被提议为 CpCo (NO) 2 (10)。使用快速扫描紫外-可见分光光度法研究了 10 与烯烃之间的反应动力学。这些实验表明，速率总体上是二阶的，二亚硝基和烯烃都是一阶的，并且报告了一系列烯烃的双分子速率常数。由相应的二聚体15和一氧化氮制备10的电子修饰衍生物，(CO2Me)C5H4Co(NO)2(16)。该配合物明显比其母体对应物更稳定，但仍然太活泼而无法分离。现在已知许多均相反应，其中有机过渡金属配合物用于将烯烃转化为其他有机材料。其中一些，例如加氢甲酰化和加氢羧化，是主要的工业过程；其他 13 个是可用于有机合成的化学计量反应。 lb 这些反应是有机金属化学中研究最深入的反应之一。大多数通过经典类型的机制进行：将烯烃配位到金属中心，然后进行插入，然后进行配体释放反应（eq la）。然而，第二种类型的机制已经
Heating (?; 5-cyclopentadienyl)(2, 3-dimethyl-2, 3-dinitrosobutane) cobalt (1), prepared from [CpCoNO] 2, NO, and 2.3-dimethyl-2-butene, with ci'. re «do-5, 6-dicarbomethoxynorbornene (2b) in aromatic solvents converted it quantitatively into 2.3-dimethyl-2-butene (4) and 3b (the adduct formed from 2b and [CpCoNO] 2/NO). The reaction was first order in [1] with kobs¿=(4.3±0.3) X 10" 4 s'1 at 75 C,£ a= 29.4±0.4 kcal/mol, and A= 1.3 X 1015 s'1. Addition of alkene 4 inhibited the reaction in a linear fashion, consistent with a mechanism involving reversible dissociation of 1 into 2, 3-dimethyl-2-butene and CpCo (NO) 2, followed by reaction of this dinitrosyl with 2b, as shown in Scheme I. This olefin exchange occurs stereospecifically since complexes 5 and 7 exclusively regenerate (£)-and (Z)-3-methyl-2-pentene, respectively. Complex 1 also undergoes olefin exchange upon photolysis in the presence of 2b with 30= 1.12 X 10" 3. Treatment of [CpCoNO] 2 with nitric oxide generates a new species which is stable in solution at room temperature. This material is too reactive to allow isolation, but its solutions can be studied spectroscopically. It exhibits two bands in the IR (1609 and 1690 cm'1) and a single resonance in the proton NMR (4.22); in the UV it absorbs at Xmax 255 nm. Adding alkene to a solution of this material rapidly produces cobalt dinitrosoalkanes (Scheme III), identical with those formed on reaction of alkenes with [CpCoNO] 2/NO. On the basis of these observations this reactive species is proposed to be CpCo (NO) 2 (10). The kinetics of the reaction between 10 and alkenes have been studied by using rapid-scan UV-visible spectrophotometry. These experiments have shown that the rate is second order overall, first order in both dinitrosyl and alkene, and the bimolecular rate constants for a series of olefins are reported. An electronically modified derivative of 10,(C02Me) C5H4Co (NO) 2 (16), was prepared from the corresponding dimer 15 and nitric oxide. This complex was noticeably more stable than its parent counterpart but was still too reactive to isolate.Many homogeneous reactions are now known in which organotransition-metal complexes are used totransform alkenes into other organic materials. Some of these, such as hydroformylation and hydrocarboxylation, are major industrial processes; 13 others are stoichiometric reactions useful in organic synthesis. lb These reactions are among the most well studied of any in organometallic chemistry. The large majority proceedby a classical type of mechanism: coordination of the alkene to the metal center, followed by an insertion and then a ligand-release reaction (eq la). However, a second type of mechanism has been