Ligand substitution and reduction reactions of decakis(isopropylisocyanide)dicobalt(II)

The reactions between decakis(isopropylisocyanide)dicobalt(II), present as [Co(CNCHMe 2 ) 5 ] 2+ in solution, and three triaryl phosphines, PPh 3 , P(C 6 H 4 Me-p) 3 , and P(C 6 H 4 OMe-p) 3 , have been studied in dichloromethane. The reactions were investigated under pseudo first-order conditions at different temperatures. A combination of conventional, stopped-flow, and infrared spectroscopy was employed in order to gain insight into the reaction mechanisms. Addition of each of the three phosphines to the Co(II) complex results in a shift in the λ max followed by increase and/or decrease in absorbance at the new wavelength. The triaryl phosphines react in the order P(C 6 H 4 OMe-p) 3 ≫ P(C 6 H 4 Me-p) 3 > PPh 3 . This is explained in terms of the electron-donating/π-acceptor properties of the phosphines. The reactions are proposed to proceed via a number of reaction pathways including ligand substitution, ligand rearrangement, disproportionation, and reduction.