53335-25-4Relevant articles and documents
Rhodium(III)-to-rhodium(I) alkyl transfer: A rhodium macrocycle which is both nucleophile and leaving group
Collman, James P.,Brauman, John I.,Madonik, Alex M.
, p. 215 - 218 (1986)
The rhodium(I) macrocycles RhI(BPDOBF2) (1a) and RhI(PPDOBF2) (1b) are strong nucleophiles toward alkyl halides and may also be alkylated by their rhodium(III) alkyl halide adducts R′-RhIII(BPDOBF2)-X and R′-RhIII(PPDOBF2)-X (2a and 2b), respectively. In the latter process, 1a,b act as both nucleophile and leaving group. We have studied the kinetics of alkyl exchange between, e.g., 1a and 2b by 1H NMR and the rate constants are (5.8 ± 0.5) × 10-3 M-1 s-1 for methyl exchange (R′ = Me, X = I) and (6.4 ± 1.0) × 10-2 M-1 s-1 for benzyl exchange (R′ = PhCH2, X = Cl). Other alkyl groups do not participate in this reaction. These data are consistent with rhodium(I) attack at carbon; the process may be viewed as a carbon-bridged two-electron transfer. Halide-bridged electron transfer is implied in the much faster exchange (k > 0.5 M-1 s-1) between 1a,b and their rhodium(III) dichloride derivatives 3a and 3b.