Infrared spectroscopy has been used to determine the relative anion affinities in CH2C12 of Rh(PPh3)2(CO)+ and Rh(AsPh3)2(CO)+via measurement of equilibrium constants for the metatheses RhL2(CO)Y + PPN+Z- = RhL2(CO)Z + PPN+Y-. Observed for L = PPh3 was the anion affinity trend NCO- ≫ O2CMe- ~ O2CPh- ≫ F- ~ NCS- > Cl- > Br- > I- ≫ ONO2 ~ O2CCF3 - ≫ OTf- ~ OC103 -. A smaller series for L = AsPh3 displayed a similar trend, but with positions of NCS- and CI- reversed. For most anion pairs studied, the equilibrium lies so far to the left or right that only limits could be calculated, given the inherent experimental limitations. For L = PPh3, the equilibrium constant for replacement of the least preferred anion by the most can be inferred as > 1019. Rh(PCy3)2(CO)Cl and Rh(PCy3)2(CO)Z (Z = NCS, NCSe, O2CMe; but not F, O2CPh, and NCO) interact strongly in solution and thus limit study of that series.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry