Influence of the nature of ligands in iridium complexes with C60 fullerene and ·P(O)(OPri)2, ·CMe3, and ·CCl3 radicals on regioselectivity of addition and stability of spin-adducts formed: an EPR study

Abstract

The addition of ·P(O)(OPri)2 (R1), ·CMe3 (R2), and ·CCl3 (R3) radicals to metallofullerenes (η2-C60)IrH(CO)(CNBut)2(o-HCB10H9CCH2PPh2-B,P) (1), (η2-C60)IrH(CO)(DIOP) (DIOP is (4R,5R)-(+)-4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane, 2), and (η2-C60)IrH(CO)(PPh3)2 (3) was studied by EPR spectroscopy. A stability study of spin adducts (SAs) of R1 radicals with complexes 1 and 2 showed that when the reactions are initiated by illumination with 366-nm light, the EPR spectra exhibit only signals of those isomers that are formed upon attack of the R1 radicals on the carbon atoms of the cis-1 and cis-2 bonds (i.e., carbon atoms of the fullerene hemisphere to which the metallofragment is attached). Investigations of the reactions of R2 and R3 radicals with complexes 1–3 initiated with 366-nm light made it possible to detect (i) regioisomers formed by adding these radicals to carbon atoms of the cis-n bonds and (ii) SAs formed by adding the radicals to carbon atoms of other bonds in complexes 1–3. The hyperfine structure of the EPR spectrum essentially depends on the spatial structure of substituents at the metal atom and allows individual regioisomers of not only phosphoryl radicals, but also carbon-centered radicals R2 and R3 with metallofullerenes 1–3 to be identified. The rate constants for addition of R2 and R3 radicals to complexes 2 and 3 were determined.