鋨金屬與釕金屬亞乙烯基化合物的合成與反應性： 碳-碳鍵的斷裂與重建

Synthesis and Reactivity of Osmium and Ruthenium Vinylidene Complexes: Cleavage and Reconstruction of Carbon-Carbon Bond

鄭呈偉(Cheng-Wei Cheng)

指導教授 ： 林英智

國立臺灣大學/理學院/化學研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.01933

摘要

探討一系列含有環戊二烯或五甲基環戊二烯基鋨或釕金屬亞乙烯基錯合物的合成與反應性。陽離子金屬亞乙烯基錯合物，可以由鋨或釕金屬乙炔基化合物(η5-C5R5)(PPh3)2M-C≡CR1 (1, M = Os, R = H, R1 = Ph; 1', M = Os, R = Me, R1 = Ph; 1a, M = Ru, R = H, R1 = Me; 1b, M = Ru, R = H, R1 = n-Bu) 和一系列鹵烷進行烷化反應得到。在化合物2和鹼反應過程中，可以觀測到金屬環丙烯基化合物 (η5-C5R5)(PPh3)2M{C=C(R1)CHR2} 的生成，然而只有3a (M = Os, R1 = Ph, R2 = CN), 3aa~3ac (M = Ru, R1 = Me, R2 = CN, Ph, CH=CH2) 和3bb (M = Ru, R1 = n-Bu, R2 = Ph) 可以被純化出來；其餘亞乙烯基錯合物，視其取代基不同會生成金屬呋喃或酯環酮化合物。金屬環丙烯基化合物3溶於氯仿時，其穩定性會受取代基R1和R2影響，而有下列排序：對於R1而言，Ph ＞ Me ＞ n-Bu，對於R2而言，CN ＞ Ph ＞ CH=CH2。呋喃化合物4e, 4ah, 4ch, 4ai, 4aj, 4ak和4ck會進一步行sigmatropic重排反應，生成酯環酮化合物5e, 5ah, 5ch, 5ai, 5aj, 5ak和5ck。重排反應的速率也會因不同取代基R1而有所差別。
一系列具有亞甲基橋鍵之雙金屬亞乙烯基錯合物[M1]=C=C(R1)CH2C(CH2R2)=C=[M2] 也被合成，但只有11da (M1 = Os, M2 = Ru, R1 = Ph, R2 = CN) 和 11db (M1 = Os, M2 = Ru, R1 = Ph, R2 = CO2Et) 能夠經由去質子反應，形成雙金屬環化合物12和13。
以陽離子鋨金屬亞丙烯基化合物14和14'和格任亞試劑作用可以得到鋨金屬炔基化合物。將此系列炔基化合物在乙醚溶劑中進行質子化，會生成穩定的亞乙烯基化合物 [(η5-C5R5)(PPh3)2Os=C=CHC(Ph)2CH2R']+ (15, 15')。然而在高溫下的狀況下，有兩種新穎的反應性被發現，一者為15a (R = H, R' = CH=CH2) 經由分子內歧化反應轉變成 [(η5-C5H5)(PPh3)2Os=C=CHCH2C(Ph)2(CH=CH2)]+ (17)，另一者為15b (R = H, R' = C(Me)=CH2) 經由分子內環化反應，生成金屬環丙二烯化合物18。將反應系統換成較缺電子的釕金屬，在乙醚溶劑下，這兩種反應依舊發生並且速率增快；除此之外，更換γ碳上的取代基也會影響反應速率。
當質子化的溶劑換成甲醇，[Ru']C≡CC(Ph)2CH2CH=CH2] (20'a) 會反應生成環碳烯化合物23'，它的結構已用單晶X射線繞射分析確定。意外的是，當釕金屬亞乙烯基化合物 [[Ru']=C=CHCH2C(Ph)2CH=CH2]+ (22'a) 溶於甲醇也會生成相同的產物23'；我們藉由氘標識和碳-13標識的實驗結果，猜測反應機構可能有牽涉骨架重排。類似的反應，將22'a溶於異丙醇，除了得到預期的化合物23'，同時也生成異丙氧基取代的環己烯化合物25c；對於25c的生成，也使用碳-13標識法確認了，原本在22'a中兩個斷開的碳-13標識碳又再度重建，我們猜測反應機構也是經由骨架重排機制。
重排機制可能牽涉金屬環丙烯基化合物，這個中間產物可由兩個雙鍵直接進行位置特異的 [2+2] 環化加成反應生成；或者是進行5-內環化反應，先得到一非古典型陽離子中間產物，再行1,2-烷基轉移生成。

關鍵字

釕金屬,鋨金屬,亞乙烯基,環化反應,重排反應

並列摘要

The reactivity of a series of cationic metal (Os, Ru) vinylidene complexes containing the cyclopentadienyl(phosphine) and pentamethylcyclopentadienyl (phophine) ligand sets are discussed. The cationic metal vinylidene complexes 2 are prepared by alkylation reactions of alkyl halides with acetylide complexes (η5-C5R5)(PPh3)2M-C≡CR1 (1, M = Os, R = H, R1 = Ph; 1', M = Os, R = Me, R1 = Ph; 1a, M = Ru, R = H, R1 = Me; 1b, M = Ru, R = H, R1 = n-Bu). Complexes 2 react with n-Bu4NOH to yield (η5-C5R5)(PPh3)2M{C=C(R1)CHR2} 3 (cyclopropenyl complexes), which are observed during the cyclization process. However, only 3a (M = Os, R1 = Ph, R2 = CN), 3aa~3ac (M = Ru, R1 = Me, R2 = CN, Ph, CH=CH2) and 3bb (M = Ru, R1 = n-Bu, R2 = Ph) are isolated and the rest further transform into 4 (furan) or 5 (lactone) depending on the various group on vinylydene ligand of 2. Among all furan complexes 4, only 4e, 4ah, 4ch, 4ai, 4aj, 4ak and 4ck could further yield the lactone complexes 5e, 5ah, 5ch, 5ai, 5aj, 5ak and 5ck via sigmatropic rearrangements, respectively. The rate of rearrangement was affected by R1. The stability of the 3 in CHCl3 follows the trend for the substituents R1 of Ph ＞ Me ＞ n-Bu and for the substituents R2 of CN ＞ Ph ＞ CH=CH2.
The bimetallic compounds of [M1]=C=C(R1)CH2C(CH2R2)=C=[M2] (11, M = Os or Ru) containing a methylene bridge are prepared, but only complexes 11da (M1 = Os, M2 = Ru, R1 = Ph, R2 = CN) and 11db (M1 = Os, M2 = Ru, R1 = Ph, R2 = CO2Et) proceed to produce bismetallic cyclic complexes 12 and 13, respectively after deprotonation.
Using cationic osmium allenylidene complexes 14 and 14' with Grignard reagents R'CH2MgX, the acetylide complexes (η5-C5R5)(PPh3)2Os-C≡CC(Ph)2CH2R' are obtained. When they are further protonated by HBF4 in diethyl ether, corresponding vinylidene complexes [(η5-C5R5)(PPh3)2Os=C=CHC(Ph)2CH2R']+ (15, 15') are afforded. Most of complexes 15 are stable even in refluxing acetonitrile. Interestingly, two novel transformations are observed at ca. 50oC, including 15a (R = H, R' = CH=CH2) to [(η5-C5H5)(PPh3)2Os=C=CHCH2C(Ph)2(CH=CH2)]+ (17) caused by intramolecular metathesis process, and 15b (R = H, R' = C(Me)=CH2) to the cyclic allene complex 18 involved a C-C bond formation giving a six-membered ring and a change of coordination to a η2-allene mode. These similar transformations are also observed in ruthenium system (20'a → 22'a, 20'b → 26') in diethyl ether under low temperature (-20oC). The rates of the two transformations are closely related to the metallic fragments and the substituents at Cγ.
Replacing diethyl ether with MeOH, the reaction of 20'a and HBF4 affords an unsaturated cyclic carbene complex 23', which is fully characterized by single-crystal X-ray diffraction analysis. Unexpectedly, dissolving 22'a in MeOH also obtains the same product 23'. The reaction mechanism is elucidated by deuterium and 13C labeling experiments results and proposed to involve a skeletal rearrangement. For comparison, complex 22'a in iPrOH yields, besides 23', the corresponding alkoxycyclohexene 25c. Formation of 25c from 22'a also involves a skeletal rearrangement with reconstruction of the C=C bond. The proposed mechanism implicates a cyclobutylidene intermediate formed via either a regiospecific [2+2] cycloaddition of two double bonds in the ruthenium-vinylidene 22'a, or via a 5-endo cyclization of 22'a giving a nonclassical ion intermediate followed by a 1,2-alkyl shift.
Two types of cationic osmium and ruthenium vinylidene complexes, [(η5-C5R5)(PPh3)2M=C=C(R1)CH2R2] and [(η5-C5R5)(PPh3)2M=C=CHC(Ph)2CH2R'], were reported. By changing different alkylation group (R2), the former vinylidene complexes have been yielded various cyclic complexes (cyclopropene, furan and lactone). The reactivity of the other type [(η5-C5R5)(PPh3)2M=C=CHC(Ph)2CH2R']+ is closely related to the R' group.

並列關鍵字

ruthenium, osmium, vinylidene, cyclization, rearrangement

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