Analysis of the Correction Published in:
J. Am. Chem. Soc. 2022, 144, 14957
All of my comments, save for just a few, have been elegantly turned a blind eye to by the authors and EiC. This is unambiguously and convincingly demonstrated in this scrutiny, which also reviews and analyzes the five changes constituting the Correction to the original Article. All five changes are also examined in somewhat greater detail below.
Change #1
"Page 14368. Scheme 1 in the published work should be replaced with the version below, in which part E has been added. The following sentence should be added to the text discussion of Scheme 1, at the end of the paragraph that begins, “To elucidate the structure of the observed [CF3Cu] species, ...”:
"Grushin and co-workers prepared and characterized a ligandless CuCF3 (−26.9 ppm in DMF) and studied the mechanism of the reaction of the ligandless CuCF3 with aryl iodides" (Scheme 1E).19b"
"Grushin and co-workers prepared and characterized a ligandless CuCF3 (−26.9 ppm in DMF) and studied the mechanism of the reaction of the ligandless CuCF3 with aryl iodides" (Scheme 1E).19b"
[To view the updated Scheme 1, click here.]
Comment:
This addition is inconsequential in terms of the overall scientific value of the report, which remains totally flawed. I have never suggested that this insignifcant, rather cosmetic change be made.
There is an error in the addition: the transformation outlined in added Scheme 1E was reported in 2011, not in 2014.
This addition is inconsequential in terms of the overall scientific value of the report, which remains totally flawed. I have never suggested that this insignifcant, rather cosmetic change be made.
There is an error in the addition: the transformation outlined in added Scheme 1E was reported in 2011, not in 2014.
Change #2
"Page 14370. The following sentences should be added on at the end of the paragraph in which Figure 2 is cited:
"X-ray diffraction studies of the single crystals of both complexes 1b and 1c show that there are significant static disorders in both structures. The crystals of complex 1b exist as a mixture of two species, [Cu(CF3)(Cl)]− and [Cu(CF3)2]−, while the crystals of complex 1c are a mixture of three species, [Cu(CF3)(I)]−, [Cu(CF3)2]−, and [CuI2]−. The structures of complexes 1b and 1c were tentatively assigned as [Cu(CF3)(Cl)]− and [Cu(CF3)(I)]−, since the unit-cell parameters of the crystal lattices of [Cu(CF3)2]− and [CuI2]− are different from those of complexes 1b and 1c. The quality of the X-ray diffraction data was not high enough to obtain detailed structural information on both complexes. The Cu−CF3 bond distances in both structures were not accurate due to the disorder."
"X-ray diffraction studies of the single crystals of both complexes 1b and 1c show that there are significant static disorders in both structures. The crystals of complex 1b exist as a mixture of two species, [Cu(CF3)(Cl)]− and [Cu(CF3)2]−, while the crystals of complex 1c are a mixture of three species, [Cu(CF3)(I)]−, [Cu(CF3)2]−, and [CuI2]−. The structures of complexes 1b and 1c were tentatively assigned as [Cu(CF3)(Cl)]− and [Cu(CF3)(I)]−, since the unit-cell parameters of the crystal lattices of [Cu(CF3)2]− and [CuI2]− are different from those of complexes 1b and 1c. The quality of the X-ray diffraction data was not high enough to obtain detailed structural information on both complexes. The Cu−CF3 bond distances in both structures were not accurate due to the disorder."
[To download the cif files, click here.]
Comment:
In other words, the authors admit that both structures are nonsense, as I predicted on the basis of the clearly unrealistic geometry parameters reported in the original article. Alas, the authors' confession does not make the report publishable. No new X-ray structural data has been added in the Correction to support the authors' claim of “full characterization” of the complexes.
Change #3
"Page 14374. The sentence beginning “It was found that the reaction occurred so fast...”, in which Scheme 5, eq 1, is cited, should be replaced by the following:
"It was found that the reaction occurred so fast that [nBu4N]+[CuI2]− 1d was generated after the mixture of CuI and nBu4NI was shaken in CH2Cl2 for 30 s and further violently stirred for 10 min, and complex 1d was isolated as a gray solid in 96% yield after evaporation of the solvent (Scheme 5, eq 1)."
"It was found that the reaction occurred so fast that [nBu4N]+[CuI2]− 1d was generated after the mixture of CuI and nBu4NI was shaken in CH2Cl2 for 30 s and further violently stirred for 10 min, and complex 1d was isolated as a gray solid in 96% yield after evaporation of the solvent (Scheme 5, eq 1)."
Comment:
This is the only satisfactory change of the handful made in the Correction. The change is pretty straightforward. As is pointed out in my critique, the originally reported procedure could not furnish the targeted complex in pure form because the reactants were used in the wrong ~0.5:1 ratio, not in the correct 1:1 ratio. The obviously wrong original prep has now been replaced with a new one which seems credible.
Why the elemental analysis data for the originally isolated solid fitted the formula [nBu4N]+[CuI2]− remains a mystery. So does the difference in the calculated values for C in the original (34.44; see p. S5) and new (34.33; see p. S5) procedures.
Reference 1b added to the Supporting Information, is irrelevant, as it deals with an X-ray structure of [nBu4N]+2[Cu2I4]2- and has nothing to do with the synthesis of [nBu4N]+[CuI2]−.
This is the only satisfactory change of the handful made in the Correction. The change is pretty straightforward. As is pointed out in my critique, the originally reported procedure could not furnish the targeted complex in pure form because the reactants were used in the wrong ~0.5:1 ratio, not in the correct 1:1 ratio. The obviously wrong original prep has now been replaced with a new one which seems credible.
Why the elemental analysis data for the originally isolated solid fitted the formula [nBu4N]+[CuI2]− remains a mystery. So does the difference in the calculated values for C in the original (34.44; see p. S5) and new (34.33; see p. S5) procedures.
Reference 1b added to the Supporting Information, is irrelevant, as it deals with an X-ray structure of [nBu4N]+2[Cu2I4]2- and has nothing to do with the synthesis of [nBu4N]+[CuI2]−.
Change #4
"In the same paragraph, the sentence beginning “A solution of equimolar [Cu(CF3)2]− and [nBu4N]+[CuI2]− in DMF reacted quickly...”, in which Scheme 5, eq 2, is cited, should be replaced by the following:
"A solution of equimolar, freshly prepared [Cu(CF3)2]− and [nBu4N]+[CuI2]− in DMF reacted quickly at room temperature to generate [Cu(CF3)(I)]−, with a conversion of 40% after 10 min (Scheme 5, eq 2).
"Scheme 5 in the published work should be replaced with the version below, which reflects the text changes described above."
"A solution of equimolar, freshly prepared [Cu(CF3)2]− and [nBu4N]+[CuI2]− in DMF reacted quickly at room temperature to generate [Cu(CF3)(I)]−, with a conversion of 40% after 10 min (Scheme 5, eq 2).
"Scheme 5 in the published work should be replaced with the version below, which reflects the text changes described above."
Comment:
The original article reports that [Cu(CF3)2]− and [CuI2]− equilibrate with [Cu(CF3)(I)]− within minutes at room temperature. The corrected version, however, states that the two react to give the mixed complex [Cu(CF3)(I)]−, while being silent of whether the reaction is reversible. The original and corrected versions of eq 2 in Scheme 5 are presented below for juxtaposition.
The original article reports that [Cu(CF3)2]− and [CuI2]− equilibrate with [Cu(CF3)(I)]− within minutes at room temperature. The corrected version, however, states that the two react to give the mixed complex [Cu(CF3)(I)]−, while being silent of whether the reaction is reversible. The original and corrected versions of eq 2 in Scheme 5 are presented below for juxtaposition.
This seemingly minor change is, in fact, crucial.
The authors failed to include the equilibrium in their kinetic models, which makes the kinetic laws presented in the paper wrong and data treatment meaningless. This is explained in detail in: II. Major Problems, Kinetic studies of my critique. To further illustrate this point, the scheme below, which does take into account the equilibrium, is totally different from those used by Shen who merely ignored the equilibrium in his kinetic studies.
The authors failed to include the equilibrium in their kinetic models, which makes the kinetic laws presented in the paper wrong and data treatment meaningless. This is explained in detail in: II. Major Problems, Kinetic studies of my critique. To further illustrate this point, the scheme below, which does take into account the equilibrium, is totally different from those used by Shen who merely ignored the equilibrium in his kinetic studies.
In an attempt to eliminate the grave problem, the authors cut the Gordian knot in the Correction by pulling a cunning "now you see it, now you don't" trick – No equilibrium, no problem.
No problem, really?
No problem, really?
Let us assume for a moment that the authors do not know whether the reaction between [Cu(CF3)2]− and [CuI2]− is reversible or not. All they say in the Correction is that these two homoleptic complexes react to produce [Cu(CF3)(I)]− at 40% conversion after 10 min at room temperature. Besides reading entirely out of context of the article, this replacement raises a sobering question:
What happens after the reaction has proceeded to 40% conversion within 10 min?
The authors are silent on that. Only three scenarios are possible, as follows.
1. The molecules and ions all of a sudden stop colliding. Something tells me that this scenario is quite unlikely and should not be considered seriously.
2. Either the composition of the reaction mixture no longer changes, or the reaction continues to incomplete conversion to eventually reach equilibrium. As shown in my
critique and additionally illustrated above, if the three species do equilibrate, then the kinetic modeling used in the article is wrong.
3. The transformation is irreversible and keeps occurring to full conversion. If this is the case, the reaction may or may not influence the kinetics of the trifluoromethylation of ArI with [Cu(CF3)(I)]−. [That should have been probed by a separate experiment though, but the authors did not bother.] The kinetics of the trifluoromethylation of ArI with [Cu(CF3)2]− will be affected, however, due to the formation of [CuI2]− in the onward trifluoromethylation with [Cu(CF3)(I)]− produced in the first step, as shown below.
What happens after the reaction has proceeded to 40% conversion within 10 min?
The authors are silent on that. Only three scenarios are possible, as follows.
1. The molecules and ions all of a sudden stop colliding. Something tells me that this scenario is quite unlikely and should not be considered seriously.
2. Either the composition of the reaction mixture no longer changes, or the reaction continues to incomplete conversion to eventually reach equilibrium. As shown in my
critique and additionally illustrated above, if the three species do equilibrate, then the kinetic modeling used in the article is wrong.
3. The transformation is irreversible and keeps occurring to full conversion. If this is the case, the reaction may or may not influence the kinetics of the trifluoromethylation of ArI with [Cu(CF3)(I)]−. [That should have been probed by a separate experiment though, but the authors did not bother.] The kinetics of the trifluoromethylation of ArI with [Cu(CF3)2]− will be affected, however, due to the formation of [CuI2]− in the onward trifluoromethylation with [Cu(CF3)(I)]− produced in the first step, as shown below.
The scheme above is very different from the simple consecutive (called “continuous” in the article) reaction kinetic model used by the authors. As follows from the reported data (Figures 4A, D and eq 2 in Scheme 5), k3 >> k1 ⪆ k2. In other words, under the conditions used for the kinetic runs, the comproportionation of [CuI2]− and [Cu(CF3)2]− occurs virtually instantaneously relative to both trifluoromethylation reactions that proceed at much slower similar rates. This suggests that the "now-you-see-it-now-you-don't" equilibrium, or even the lack thereof, should have a profound effect on the kinetic profile of the reaction. The simulated graphs below demonstrate that.
For the simulation, the initial ArI to [Cu(CF3)2]− molar ratio was set at 10 as in the actual run, k1 = 3.3k2 as stated in the article (Figure 8), and the comproportionation (reversible or irreversible) orders of magnitude faster than the trifluoromethylation.
Regardless of whether the comproportionation of [Cu(CF3)2]− and [CuI2]− is reversible or not, the failure to include this transformation in the modeling makes the reported kinetic data treatment invalid and the conclusions drawn from it misleading.
Regardless of whether the comproportionation of [Cu(CF3)2]− and [CuI2]− is reversible or not, the failure to include this transformation in the modeling makes the reported kinetic data treatment invalid and the conclusions drawn from it misleading.
Change #5
"Page 14378. In ref 19, the original citation should be identified as part (a), with the new text and new ref 19b, given below as ref 1, added, as follows: (19) … (b) For mechanistic investigation of a ligandless CuCF3 with ArI, see: Konovalov, A. I.; Lishchynskyi, A.; Grushin, V. V. Mechanism of Trifluoromethylation of Aryl Halides with CuCF3 and the Ortho Effect. J. Am. Chem. Soc. 2014, 136, 13410−13425."
Comment:
Of the dozen or so reports that should have been cited in the original article (see my critique), the authors selected only one for addition in the Correction. And this only chosen publication is... our paper. Perhaps one would have thought that I am supposed to be flattered but in fact I am not.
Of the dozen or so reports that should have been cited in the original article (see my critique), the authors selected only one for addition in the Correction. And this only chosen publication is... our paper. Perhaps one would have thought that I am supposed to be flattered but in fact I am not.
