Recent Advances in N-Heterocyclic Carbene Coinage Metal Complexes in A3-Coupling and Carboxylation Reaction
, Marco Sirignano 1,†, Simona Russo 1,†, Rubina Troiano 1, Annaluisa Mariconda 2,* and Pasquale Longo 1
Round 1
Reviewer 1 Report
Dear authors,
It is with pleasure reading your manuscript.
The main question addressed by the research is Recent Advances in N-Heterocyclic Carbene Coinage Metal Complexes in A3-Coupling and Carboxylation Reaction. Compared with other published, it added synthetic conditions.
The manuscript is well written and in my opinion, it addresses all the main aspects of the topic. The work is well organized and it contributes to the field.
Best wishes,
Author Response
The authors would like to thank Reviewer 1 for his/her comment.
Reviewer 2 Report
Comments:
This review paper for “Recent Advances in N-Heterocyclic Carbene Coinage Metal Complexes in A3-Coupling and Carboxylation Reaction” was presented by Annaluisa Mariconda and coworkers. Overall, this review manuscript appears to be adequate, and the investigation into the integration and exploration of NHC ligand-based coordination complexes in this area is comprehensive, providing readers with a comprehensive overview of the topic. I believe that this manuscript is suitable for publication in the Catalysts journal and has the potential to captivate a broad readership. Therefore, I recommend accepting the manuscript. However, there are still some issues that the authors need to address. Please refer to the comments below for further feedback.
1. "The caption for 5a in Figure 4 is incorrect, please revise it. Additionally, please add the following reference: “N-Heterocyclic Carbene (NHC)–Copper(I) Complexes as Catalysts for A3 Reactions”, Synlett 2013, 24, 1190–1192.
2. Could the authors summarize the advantages and disadvantages of using NHC ligands in metal complexes for A3-coupling and CO2 fixation reactions to help readers understand the characteristics of these complexes?
Author Response
The authors would like to thank Reviewer 2 for his/her annotations. Figure 4 caption for compound 5a has been revised; the required reference regarding NHC-Copper complexes has been cited (reference 16).
The conclusion paragraph has been updated by adding details regarding the advantages of using a NHC metal complex, rather than an inorganic metallic salt, both in the case of A3 coupling and CO2 fixation.
Reviewer 3 Report
The review summarizes nicely a work relevant to silver and gold-catalyzed transformations that attracted the attention of scientists in recent years. However, due to serious formating issues and some missing literature, major revisions are required, before the article is suitable for publishing. My comments are summarized bellow:
- Page 1 – ”Complexes of monocationic coinage metals, featuring…” this senetence is a different font from the rest, because it is copied from the abstract. I recommend at least changing it to the correct font, and maybe some variation from the abstract should be considered…
- Number all the compounds in the schemes, and in the text refere to the numbers of the compunds. It will read easier.
- Scheme 2 – the catalytic cycle should be revised
- Figure 1 R groups should be changed to :
1a - Me
1b - CH2Ph
1c - Ph
1d – t-Bu
- Within the text, all the compound numbers should be bold.
- The discussion related to the reference 15 and the structure of the complexes is not understandable. If the authors intend to keep this text in the review, they should support it with the drawings of the structures, to explain, what the complexes look like. As it is, it is not really clear and it is confusing.
- Scheme 3 is redundant, it depits the same reaction mechamism, as proposed in the scheme 2. The reviver suggests that Scheme 3 is used instead of the scheme 2, as it depicts the situation clearly.
- ”using a saturated heterocycle compared to an unsaturated one” – perhaps replace with: ”using a complexes with saturated N-heterocyclic carbene based ligand (6a,b), compared to the complex with unsaturated ones (5a-d).”
- Do not start the sentence with: “So,…” (page 8), under the Table 3.
- “and this was in line with what has been reported in the literature about obtaining enantiomers with gold complexes.” (page 13) – it should be specified, what was reported in the literature and the reference to that report should be provided.
- For the silver-NHC catalyzed A3 coupling, the following reference should be included: Appl Organomet Chem 2023, 37(4), e6994. https://doi.org/10.1002/aoc.699410
- In structure 31, the delocalized bond of the carbene is missing. Unify throughout
- Capture and discussion around the scheme is about gold, but the catalytic cycle shows copper. Also, in the disuccion before the scheme, relevant to the DFT calculation, the complex 5a is mentioned, but it is not anywhere in the scheme to be found.
- The gold complex 5a is also mentioned within the section 3.2.1. but it is not depicted and the author is not redirected to where to look for its structure.
- In scheme 9, provide the yields, that are discussed in the text (and the numbers of compounds, as already mentioned in a previous comment).
- Section 3.2.2. comment on yields of the transformation, provide the range of yields to the scheme, and number the compounds in the scheme 11
- Table 29 – the number the compounds in the reaction and do not use XYZ.
- Page 35, Figure 18 is mentioned in the text, but nowhere to be found.
- Any of the tables do not have lines to separate the entries, but out of sudden 31 has lines. Unify this (I suggest deleting lines).
- Every table which shows any optimization should also show the reaction which is being optimized.
- At the page 38, the table number is 21 and should be 33. Delete the lines between the entries.
Author Response
The authors thanks for Reviewer 3's annotations and thank him/her.
The queries have been addressed; particularly, we made sure every mentioned compound throughout the text had a number in bold format, and the same was mentioned in the discussion. Yields were reported when available from the original manuscripts. The mentioned formatting issues have been resolved and reaction Schemes have been added on top of every Table, when missing.
Following, a point-by-point response to each additional annotation is reported:
Q1 Page 1 – ”Complexes of monocationic coinage metals, featuring…” this sentence is a different font from the rest, because it is copied from the abstract. I recommend at least changing it to the correct font, and maybe some variation from the abstract should be considered…
A1 The sentence has been changed to “monocationic coinage metal complexes with a d10 electronic configuration are effective catalysts for alkyne activation due to metal donation from p to s and metal to p* back-bonding”, and the same concept was elided from the abstract.
Q2 Scheme 2 – the catalytic cycle should be revised
A2 Scheme 2 and former Scheme 3 have been merged as a single, more detailed catalytic pathway, indicated as Scheme 2.
Q3 Figure 1 R groups should be changed to :
1a - Me
1b - CH2Ph
1c - Ph
1d – t-Bu
A3 Figure 1 R groups abbreviations have been changed, throughout the text as well.
Q4 The discussion related to the reference 15 and the structure of the complexes is not understandable.
If the authors intend to keep this text in the review, they should support it with the drawings of the structures, to explain, what the complexes look like. As it is, it is not really clear and it is confusing.
A4 The abbreviations in the structures have been modified; also, the discussion regarding their synthesis has been revised.
Q5 ”using a saturated heterocycle compared to an unsaturated one” – perhaps replace with: ”using a complexes with saturated N-heterocyclic carbene based ligand (6a,b), compared to the complex with unsaturated ones (5a-d).”
A5 The suggested change has been made.
Q6 Do not start the sentence with: “So,…” (page 8), under the Table 3.
A6 The suggested change has been made.
Q7 “and this was in line with what has been reported in the literature about obtaining enantiomers with gold complexes.” (page 13) – it should be specified, what was reported in the literature and the reference to that report should be provided.
A7 A reference to a detailed review concerning enantioselective gold catalysis has been added; W. Zi, F.D. Toste, Chem. Soc. Rev. 45 (2016) 4567-4589 (reference 38).
Q8 For the silver-NHC catalyzed A3 coupling, the following reference should be included: Appl Organomet Chem 2023, 37(4), e6994. https://doi.org/10.1002/aoc.699410
A8 The suggested reference has been added (reference 42)
Q9 In structure 31, the delocalized bond of the carbene is missing. Unify throughout
A9 The suggested correction has been made.
Q10 Capture and discussion around the scheme is about gold, but the catalytic cycle shows copper.
Also, in the discussion before the scheme, relevant to the DFT calculation, the complex 5a is mentioned, but it is not anywhere in the scheme to be found.
A10 The catalytic cycle has been corrected to the right Scheme; also, an additional Figure depicting the mentioned complex has been added.
Q11 Page 35, Figure 18 is mentioned in the text, but nowhere to be found.
A11 Specification of the page allocation for Figure 18 has been added.
Round 2
Reviewer 3 Report
The following two issues should be resolved before the article is in the form
- The reviewer still has a bit doubts regarding the discussion relevant to reference 15. If the authors wish to discuss a dimer with cis/trans geometry, it should be depicted what i tis. Just from the text, the reader deos not know what the Ag-Ag dimer really is. I recommend adding a structures.
- Complex 29, used for the A3 couling contam a phenyldiamin backbone and not ethylenediamine (complex 6b in the original literature, nota 6a). Replace the curent structure with:
Comments for author File: 
Comments.pdf
Author Response
The authors thank Reviewer 3 for the further comments.
Figure 3 has been changed to a detailed depiction of the solid state structures of the mentioned complexes (3a and 4), both as Chemdraw structures and X-ray crystal structures.
Figure 15 has been revised with complex 29 correct structure.
