Synthesis, Characterization, Solution Behavior and Theoretical Studies of Pd(II) Allyl Complexes with 2-Phenyl-3H-indoles as Ligands
, Mercè Rocamora 1, Gabriel Aullón 1,2, Mercè Font-Bardía 3, Teresa Calvet 4 and Concepción López 1,*Round 1
Reviewer 1 Report
Please find my comments about the results and the presentation below:
Why was the word "cinnamyl" written in italc? Line 57: The word "Chemistry" should be lowercase. In the Materials and methods chapter, authors should complete the data on the apparatus provided. Line 416: Authors should provide the volumes of organic solvents used. Line 475: Please delete "}".Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Allylic substitutions are one of the most important application of palladium chemistry. The authors describe here the synthesis, characterization, and catalytic activity of a new kind of Pd(II) Allyl Complexes with 2-3 Phenyl-3H-indoles as Ligands.
These compounds have been well characterized by elemental analyses, mass spectrometry and IR spectroscopy, and their catalytic activities were preliminarily tested in the allylic substitution by using cinnamyl acetate as the allylic source. This paper is well prepared and I suggest it is accepted after minor revision:
(1) It is better if the conversion could be given in Scheme 1.
(2) Did the authors ever compare the catalytic activity of the catalyst they prepared and the the normal catalyst (such as allylpalladium chloride dimer)?
(3) Some typical examples on the allylic substitutions by using Pd should be cited, like Angew. Chem. Int. Ed. 2012, 51, 2968-2971 and Chem. Commun. 2013, 49, 8190-8192. And in the future, maybe the authors will find more interesting results if they test their catalyst in these more challenging substrates as mentioned in the references above.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
In the manuscript „Synthesis, Characterization, Solution Behavior and Theoretical Studies of Pd(II) Allyl Complexes with 2-Phenyl-3H-indoles as Ligands“ Lopez and coworkers present the analysis of palladium allyl complexes incorporating a neutral indole ligand. The configuration and conformation is analyzed in detail in the solid state by single crystal analysis, in solution by VT-NMR analysis and in silico by DFT calculations. This is correlated with the behavior of these complexes as catalyst for a Tsuji-Trost-type test reaction revealing selectivity for the unbranched products.
Palladium allyl complexes are well-known and have been investigated in detail with respect to their application in region- and enantioselective allylation reactions. Herein, their specific conformation and rapid interconversion of stereoisomers is of key importance for reactivity and selectivity. While it is difficult in general to directly correlate reaction selectivities with observable structures of catalysts due to the Halpern limitation, the analysis of important factors driving selectivity should attract the interest of the general readership of Catalysts as it provides solid ground for future developments.
In order to improve the quality of the manuscript further, the authors may want to address the following issues:
- Page 2, lines 53-57: It is interesting to note that A and B are more cytotoxic than cisplatin in some cell lines, but it would be surprising that the free ligands shares this property due to the specific platinum mode of action. In addition, it is not clear to me, why these findings render the new indole ligands “valuable and versatile ligands in coordination and organometallic chemistry”.
- Scheme 2: Redrawing of the scheme with consistent bond lengths and angles is recommended.
- Scheme 3: The header of the scheme reads “main steps of the mechanism for the […] allylic alkylation”. However, the complete mechanism including attack of the nucleophile and subsequent coordination changes on palladium is not depicted.
- Page 11, line 324-331: The authors may want to include some relative energy differences between E, A, and C in the text for clarity. Given that no discrete solvent molecules were included in the computational model, is an accuracy of 0.01 kcal for the energy levels appropriate?
- Page 13, line 418: Crystals were collected twice.
Author Response
see attached file
Author Response File: Author Response.pdf
