203249-23-4Relevant academic research and scientific papers
EPR, electronic spectra, and electron transfer properties of the 17 electron carbonylhydrotris(triphenylphosphine)rhodium(II) cation
Menglet, Dmitri,Bond, Alan M.,Coutinho, Kevin,Dickson, Ron S.,Lazarev, Georgii G.,Olsen, Scott A.,Pilbrow, John R.
, p. 2086 - 2089 (1998)
An unusually stable five-coordinate monomeric divalent rhodium complex, [Rh(II)(H)(CO)(PPh3)3]+, is produced by bulk oxidative electrolysis or chemical oxidation of Rh(I)(H)(CO)(PPh3)3 in dichloromethane. Consequently, odd as well as even electronic configurations are available in this well- known catalytic system. The EPR and electronic spectra of electrogenerated paramagnetic 17-electron cation [Rh(II)(H)(CO)(PPh3)3]+ have been obtained at low temperatures as has the EPR spectrum of the deuterated analogue. Computer simulation of the EPR spectra of the hydride and deuteride complexes reveals three g-values and anisotropic coupling constants for hydrogen, phosphorus, and rhodium. One of the phosphorus coupling constants is very large (A1 = 175.0 G; A2 = 176.0 G; A3 = 230.0 G). This may be accounted for if [Rh(II)(H)(CO)(PPh3)3+ has the square pyramidal structure, and substantial mixing of the singly occupied metal orbital and the apical phosphorus s-orbital are considered. NMR measurements on mixture of Rh(I)(H)(CO)(PPh3)3 and [Rh(II)(H)-(CO)(PPh3)]+ are consistent with a very fast electron self-exchange reaction and the heterogeneous charge- transfer rate constant for the [Rh(II)(H)(CO)(PPhh3)3](+/0) redox couple also is very fast. One electron electrochemical oxidation of [Rh(II)(H)(CO)(PPh)3]+ to [Rh(III)(H)(CO)(PPh3)3]2+ is followed by a very fast reductive elimination reaction (loss of proton) which generates [Rh(I)(CO)(PPh3)3]+.
