3 research outputs found
Rhodium Complexes in PâH Bond Activation Reactions
The feasibility of oxidative addition of the PâH bond of PHPh2 to a series of rhodium complexes to give mononuclear hydridoâphosphanido complexes has been analyzed. Three main scenarios have been found depending on the nature of the L ligand added to [Rh(Tp)(C2H4)(PHPh2)] (Tp= hydridotris(pyrazolyl)borate): i)â
clean and quantitative reactions to terminal hydridoâphosphanido complexes [RhTp(H)(PPh2)(L)] (L=PMe3, PMe2Ph and PHPh2), ii)â
equilibria between RhI and RhIII species: [RhTp(H)(PPh2)(L)]â[RhTp(PHPh2)(L)] (L=PMePh2, PPh3) and iii)â
a simple ethylene replacement to give the rhodium(I) complexes [Rh(Îș2âTp)(L)(PHPh2)] (L=NHCsâtype ligands). The position of the PâH oxidative additionâreductive elimination equilibrium is mainly determined by sterics influencing the entropy contribution of the reaction. When ethylene was used as a ligand, the unique rhodaphosphacyclobutane complex [Rh(Tp)(η1âEt)(ÎșC,PâCH2CH2PPh2)] was obtained. DFT calculations revealed that the reaction proceeds through the rate limiting oxidative addition of the PâH bond, followed by a lowâbarrier sequence of reaction steps involving ethylene insertion into the RhâH and RhâP bonds. In addition, oxidative addition of the PâH bond in OPHPh2 to [Rh(Tp)(C2H4)(PHPh2)] gave the related hydride complex [RhTp(H)(PHPh2)(POPh2)], but ethyl complexes resulted from hydride insertion into the Rhâethylene bond in the reaction with [Rh(Tp)(C2H4)2].The generous financial support from AEI/FEDER, UE (CTQ2017â83421âP, C.T.), Gobierno de AragĂłn/FEDER (GA/FEDER, Inorganic Molecular Architecture Group E08_17R; C.T.) and the Netherlands Organization for Scientific Research (NWO) (TOP Grant 716.015.001, B.dB) is gratefully acknowledged. V.V. thanks MINECO/FEDER for an FPI fellowship.Peer reviewe