Solution and solid state NMR studies of some selenium analogues of auranofin (an anti-arthritic gold drug)

Three mixed ligand complexes of gold(Il) with phosphines and sclenones, [Et3PAuSe=C <]Br as analogues of auranofin (Et3PAuSR) have been prepared and characterized by elemental analysis, IR and NMR methods. A decrease in the I R frequency of the C=Se mode of selenones upon complexation is indicative of selenone binding to gold(I) via a selenone group. An upfield shift in C-13 NMR for the C=Se resonance of the selenones and downfield shifts in P-31 NMR for the R3P moiety are consistent with the selenium coordination to gold(I). C-13 solid state NMR shows the chemical shift difference between free and bound selenone to gold(l) for ImSe and DiazSe to be ca 10 and 17 ppm respectively. Large 77 Se NMR chemical shifts (55 ppm) upon complexation in the solid state for [Et(3)PAuDiazSe]Br compared to [Et(3)PAulmSe]Br (10 ppm) indicates the former to be more stable and the Au-Se bond to be stronger than in the latter complex.