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Facile Carbon–Carbon Bond Formation and Multiple Carbon–Hydrogen Bond Activations Promoted by Methylene-Bridged Iridium/Ruthenium Complexes

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journal contribution
posted on 14.11.2011, 00:00 authored by Tiffany J. MacDougall, Steven J. Trepanier, Jason L. Dutton, Michael J. Ferguson, Robert McDonald, Martin Cowie
The methylene-bridged complex [IrRu(CO)4(μ-CH2)(dppm)2][BF4] (1; dppm = μ-Ph2PCH2PPh2) reacts with 1,1-dimethylallene and 1,2-butadiene, resulting in coupling of the cumulene and the bridging methylene group, yielding the complexes [IrRu(CO)411-Me2CCCH2CH2)(dppm)2][BF4] (2) and [IrRu(CO)411-MeCHCCH2CH2)(dppm)2][BF4] (3), respectively, in which the resulting hydrocarbyl fragment is chelating on iridium. Reaction of 1 with 1,1-difluoroallene initially yields the analogous insertion product [IrRu(CO)411-F2CCCH2CH2)(dppm)2][BF4] (6), which slowly converts to [IrRu(CO)311-F2CCCH2CH2CO)(dppm)2][BF4] (7) by carbonyl migratory insertion. Reaction of 1 with propadiene leads to the elimination of 1,3-butadiene and the formation of [IrRu(CO)4(dppm)2][BF4]. In the presence of excess 1,1-dimethylallene, compound 2 reacts further via multiple C–H bond activations to yield [IrRu(CO)31-C(CH2CH3)C(CH3)2)(μ-κ12-CCC(CH3)CH2)(dppm)2][BF4] (8) with the elimination of H2, together with [IrRu(CO)31-C(CH2CH3)C(CH3)2)(μ-κ12-CCCH(CH3)2)(dppm)2][BF4] (9). Complex 2 also reacts with propadiene to generate [IrRu(CO)31-C(CH2CH3)C(CH3)2)(μ-κ12-CCCH3)(dppm)2][BF4] (10) and with 1,2-butadiene to yield [IrRu(CO)31-C(CH2CH3)C(CH3)2)(μ-κ12-CCCH2CH3)(dppm)2][BF4] (11) and [IrRu(CO)31-C(CH2CH3)C(CH3)2)(μ-κ12-CCCHCH2)(dppm)2][BF4] (12).