New oxorhenium(V) compound for catalyzed oxygen atom transfer from picoline N-oxide to triarylphosphines.
The synthesis and characterization of a new oxorhenium(V) compound is reported; it is [MeReO(edt)(bpym)], 8, where edt = 1,2-ethanedithiolate and bpym = 2,2'-bipyrimidine. Compound 8 was characterized by NMR spectroscopy and single-crystal X-ray analysis. It exists as a six-coordinate Re(V) compound comparable to the previously known [MeReO(edt)(bpy)] and [MeReO(mtp)(bpy)]. Compound 8 catalyzes the oxygen-atom-transfer reaction PicO + PZ3 --> Pic + Z3PO, whereas the other two do not. The kinetics of this reaction with catalyst 8 follows the rate law -d[PicO]/dt = k[8][PicO]/(1 + c[PZ3]). With different phosphines, the rate law has the same k value, 4.17 L mol(-1) s(-1), but different c values. For tritolylphosphine, c = 67.5 L mol(-1) in benzene at 25 degrees C. A mechanism has been proposed to account for these findings. The data establish that an open coordination site on rhenium is necessary for oxygen-atom-transfer reactions.
Cai
Yang
Y
Ames Laboratory and Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
Ellern
Arkady
A
Espenson
James H
JH