Synthesis and characterization of Cp∗MCl(PR3)(S or W-η1-butadienesulfonyl) compounds of rhodium and iridium

A metathesis reaction of [Cp∗MCl2(PR3)] [M = Rh, R = Ph (1), Me (3); M = Ir, R = Ph (2), Me (4)] takes place in the presence of potassium butadienesulfinate (SO2CHCHCHCH2)K (9) to afford the mononuclear compounds [Cp∗M(Cl)(PR3)(η1-SO2CHCHCHCH2)] [M = Rh, R = Ph (11S), (11W); M = Rh, R = Me (13S), (13W)] and [M = Ir, R = Ph (12S); M = Ir, R = Me (14S), (14W)] under different reaction conditions. The addition of PR3 (R = Ph, Me) to Cp∗Ir(Cl)[(1,2,5-η)-SO2CHCHCHCH2] (7) affords the corresponding iridium isomers 12S, 12W and 14S, in a non-selective reaction, along with the corresponding dichloride compounds 2 or 4. The 1H and 13C{1H} NMR data are consistent with the butadienesulfonyl ligands coordinated exclusively through the sulfur atom, and they show the presence of two isomers, described as the S and W conformers, which can be isolated separately. There is clear evidence that these isomers correspond to the kinetic and thermodynamic derivatives, respectively.