4- butane reaction with iridium complexes

Hydrogen addition to Ir(CO)(dppe)(X) leads first to the isomer with X trans to one phosphorus of dppe in a reversible reaction. This kinetic isomer then rearranges to the thermodynamic isomer that has CO trans to a phosphorus atom of dppe. For X = H or PPh3, no rearrangement of the initially formed product is observed . Addition of H2 to an iridium complex containing the optieally active diphosphine chiraphos [bis(S),(S)-2,3-(diphenylphosphino)butane] was described - . The H2 addition to analogues of... 

IrsMo) prepared from the bimetallic carbonyl complex was somewhat more active for the -butane reaction at 488 K than a pure iridium catalyst, but high ethane selectivity was retained (1.43). The IraMoa complex gave a less active catalyst, with a lower value of S2 (1.08). The addition of zirconium to platinum (Pt7sZr25/C) lowered the rate of ethane hydrogenolysis about 20-fold, and raised the activation energy. ... 

The reactions of butane-2,3-diol by HCF in alkaline medium using Ru(III) and Ru(VI) compounds as catalysts leads to similar experimental rate equations for both the reactions. The mechanism involves the formation of a catalyst-substrate complex that yields a carbocation for Ru( VI) or a radical for Ru(III) oxidation. The role of HCF is in catalyst regeneration. The rate constants of complex decomposition and catalyst regeneration have been determined.89 A probable mechanism invoving formation of an intermediate complex has been proposed for the iridium(III)-catalysed oxidation of propane- 1,2-diol and of pentane-1,5-diol, butane-2,3-diol, and 2-methylpentane-2,4-diol with HCF.90-92 The Ru(VIII)-catalyzed oxidation some a-hydroxy acids with HCF proceeds with the formation of an intermediate complex between the hydroxy acid and Ru(VIII), which then decomposes in the rate-determining step. HCF regenerates the spent catalyst.93... 

Further studies by Bargon and co-workers used PHIP to obtain evidence for coordination of styrene hydrogenation products to rhodium through the arene group." Upon reaction of styrene and p-Wz with [Rh(cod)(dppbu)]BF4 as catalyst (dppbu= l,4- A(diphenylphosphino)butane), polarized resonances for the ethyl resonances of the ethylbenzene product appeared in the NMR spectrum in addition to resonances further upfield with the same coupling constants. The fact that the former resonances were downfield relative to those of free ethylbenzene led to the suggestion that the ethylbenzene product remained bound to the Rh center immediately after it was produced (Scheme 9). (The iridium analogs of these complexes are thermodynamically stable and had been isolated and... 

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