Alkyne/Methylene Coupling at Adjacent Iridium/Osmium Centers: Facile Carbon鈭扖arbon and Carbon鈭扥xygen Bond Formation
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- 作者：Tiffany J. MacDougall ; Angela Llamazares ; Oliver Kuhnert ; Michael J. Ferguson ; Robert McDonald ; Martin Cowie
- 刊名：Organometallics
- 出版年：2011
- 出版时间：March 14, 2011
- 年：2011
- 卷：30
- 期：5
- 页码：952-964
- 全文大小：1085K
- 年卷期：v.30,no.5(March 14, 2011)
- ISSN：1520-6041
文摘
The methylene-bridged complex [IrOs(CO)4(渭-CH2)(dppm)2][CF3SO3] (dppm = 渭-Ph2PCH2PPh2) (3) can be synthesized by the addition of diazomethane to [IrOs(CO)5(dppm)2][CF3SO3] (1) or [IrOs(CO)4(dppm)2][CF3SO3] (2). Reaction of 3 with dimethyl acetylenedicarboxylate (DMAD) leads to the insertion of the alkyne into the iridium鈭抍arbon bond, yielding both [IrOs(CO)4(渭-魏1:魏1-C(CO2CH3)鈺怌(CO2CH3)CH2)(dppm)2][CF3SO3] (5) and [IrOs(CO)3(渭-魏1:魏1-C(CO2CH3)鈺怌(CO2CH3)CH2)(dppm)2][CF3SO3] (6), each of which can be obtained as the exclusive product under either CO or an Ar purge, respectively. Hexafluorobutyne (HFB) fails to react with 3, but reacts with [IrOs(CO)3(渭-CH2)(dppm)2][CF3SO3] (4) yielding [IrOs(CO)3(渭-魏1:魏1-C(CF3)鈺怌(CF3)CH2)(dppm)2][CF3SO3] (7). Reaction of 7 with diazomethane results in the insertion of a second methylene unit into the iridium鈭抍arbon bond, yielding [IrOs(CO)3(渭-魏1:魏1-CH2(CF3)C鈺怌(CF3)CH2)(dppm)2][CF3SO3] (9), which can be characterized by NMR spectroscopy only at low temperatures owing to deinsertion of the iridium-bound methylene group at ambient temperature. Compound 6 also reacts with diazomethane but in this case results in the formation of a new carbon鈭抩xygen bond between the newly introduced methylene unit and a carbonyl oxygen of the inserted DMAD fragment. This bond formation is accompanied by carbon鈭抙ydrogen bond activation of the original osmium-bound methylene group, yielding [IrOs(CO)3(渭-H)(渭-魏1:魏1:魏1-CH2OC(OCH3)鈺怌C(CO2CH3)鈺怌H)(dppm)2][CF3SO3] (8). Attempts to insert a methylene unit into the iridium鈭抍arbon bond of the alkyne-bridged complexes [IrOs(CO)3(渭-魏1:魏1-RC鈺怌R)(dppm)2][CF3SO3] (R = CO2Me (12), CF3 (13)) yields the C3-bridged complex [IrOs(CO)3(渭-魏1:魏1-CH2(CF3)C鈺怌CF3)(dppm)2][CF3SO3] (14) in the case of 13, but no further methylene incorporation is observed. Compound 12 reacts with diazomethane to give a number of unidentified products under a variety of conditions. The reactivities of the aforementioned complexes are compared to that of related late metal combinations.