Reductively induced homolytic carbon–carbon bond cleavage in Co(CO)3(PPh3)(COCF3)

Comparison of the Thermal and Reductive Decarbonylation of a Rhodium Trifluoroacetyl Diphosphine Complex

“…27 Nevertheless, the partial solution confirmed our proposed decarbonylation step. The CO stretching frequency characteristic of a terminal carbonyl, the inequivalence of the phosphine NMR resonances, and the appearance of Rh-F coupling in the 19 F NMR spectrum are all consistent with the proposed structure. Nevertheless, it should be noted that the F NMR spectrum, for which the signal-to-noise ratio was quite good, displayed additional minor resonances very similar to the major resonances but at different chemical shifts, perhaps representing different isomers of the trifluoromethyl complex produced as minor products.…”

“…The thermal reactivity of 1 was followed by NMR, with the starting complex showing a doublet at 16.8 ppm in its 31 P NMR and a singlet at -69.6 ppm in its 19 F NMR spectrum in CD 2 Cl 2 . Over the course of 3 days in CD 2 Cl 2 solution at room temperature these peaks decreased in intensity and major new ones appeared at -21.7 (pd) and 0.5 (ddq) ppm in the 31 P NMR and 1.7 (dt) ppm in 19 F NMR. Coupling constants of these peaks are presented in Table 2.…”

“…Chemical Reduction of 1. Complex 1 was reduced in THFd 8 with THF solutions of the mono-and dipotassium salts of benzophenone (KBP and K 2 BP), and the progress of the reaction was monitored by IR, 31 P NMR, and 19 F NMR. IR spectra showed that during the reduction of 1 its carbonyl stretching band at 1680 cm -1 (cf.…”

“…Unfortunately, preliminary studies of the reduction of the well-known acetyl complex Rh(dppp)(COCH 3 )I 2 failed to show any evidence for the proposed ETC decarbonylation reaction and also proved difficult to follow by NMR. We therefore used our experience with perfluoroalkyl complexes to prepare the previously unreported Rh(dppp)(COCF 3 )I 2 (1), which would allow both 31 P and 19 F NMR to be conveniently used to follow the course of the reaction and the fate of the acyl group. Such an approach proved quite successful in our studies of the similar Co(CO) 3 (PPh 3 )(COCF 3 ) system.…”

“…Such an approach proved quite successful in our studies of the similar Co(CO) 3 (PPh 3 )(COCF 3 ) system. 19 Much to our surprise, while studying its electrochemistry we discovered that complex 1 underwent thermal decarbonylation in solution under ambient conditions, though at a rate slow enough that it did not interfere with the reductive studies. Therefore, we have also studied this unexpected thermal decarbonylation and found that it proceeds via a path quite different from that of the reduction reaction.…”