- Homo- and heterobimetallic complexes of rhodium, iridium, palladium, and platinum containing a dimetalated olefin
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Reaction of [Rh2Cl2(μ-CO)(Ph2Ppy)2] with electrophilic acetylenes gives the dimetalated olefin derivatives [Rh2Cl2(μ-RC=CR′)(Ph2PPy)2] (R = R′ = CO2Me, CF3; R = CO2Me, R′ = H). These add carbon monoxide in terminal sites to form [Rh2Cl2(CO)2(μ-RC=CR′)(Ph 2PPy)2]. Chloride abstraction from [Rh2Cl2(μ-CO)(Ph2Ppy)2] by silver perchlorate yields [Rh2Cl(μ-CO)(Ph2Ppy)2]ClO4 which adds carbon monoxide to give [Rh2(CO)2(μ-Cl)(Ph2Ppy)2]ClO 4. Dimethyl acetylenedicarboxylate (DMAD) also forms the dimetalated olefin complex [Pd2Cl2(μ-DMAD)(Ph2Ppy)2] with [Pd2Cl2(Ph2Ppy)2] while [PtBr2(Ph2Ppy)2] adds to [IrBr2(CO)2)]- to give [PtIrBr3(CO)(Ph2Ppy)2]. Heterobimetallic, dimetalated olefin complexes [IrRhCl2(CO)(μ-CO)(μ-RC=CR)(DPM)2] (R = CO2Me, CF3) are formed from the appropriate acetylene and [IrRh(CO)2(μ-Cl)(DPM)2]Cl. Isomers with the terminal carbonyl bound to iridium and to rhodium are both formed. Loss of one carbonyl ligand occurs at reflux under nitrogen to form the metal-metal bonded complexes [IrRhCl2(CO)(μ-RC=CR)(DPM)2] (R = CO2Me, CF3) Chloride abstraction from [IrRhCl2(CO)(μ-CO)(μ-DMAD)(DPM)2] by silver perchlorate under carbon monoxide yields [IrRh-CO)2Cl(μ-CO)(μ-DMAD)(DPM)2]ClO4 in which the terminal carbonyls are both bound to rhodium. This is readily and reversibly decarbonylated to [IrRhCl(CO)2(μ-DMAD)(DPM)2]ClO4 which contains a metal-metal bond and in which the carbonyl groups are now bound to iridium. The reverse process occurs by initial attack of carbon monoxide at rhodium. The mononuclear complexes [Ir(CO)X(Ph2Ppy)2] (X = Cl, Br) are readily formed, but diiridium complexes bridged by 2-pyridyldiphenylphosphine could be obtained only with difficulty and attempts to form related rhodium-iridium dimers failed. The infrared and 13C and 31P NMR spectra of the new complexes are discussed as are possible mechanisms for the interconversions of [IrRhCl(CO)2(μ-CO)(μ-DMAD)(DPM)2]ClO4 and [IrRhCl(CO)2(μ-DMAD)(DPM)2]ClO4.
- Mague, Joel T.
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p. 918 - 926
(2008/10/08)
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