Crystal Structures of Half-Sandwich Ru(II) Complexes, [(η⁶-p-Cymene)(3-chloro-6-(1H-pyrazol-1-yl)pyridazine)Ru(X)]BF₄, (X = Cl, Br, I)

Round 1

Reviewer 1 Report

The synthesis, spectroscopic characterization in both solution and solid-state of three new isostructural half-sandwich ruthenium(II) complexes is presented. In addition, the structures obtained have been compared to those theoretical predicted by DFT calculations. Taking into account the current relevance of arene-ruthenium(II) complexes in medicinal chemistry and catalysis, the manuscript herein presented could be of interest for the readers Molbank and for that reason acceptance is recommended. However, I think that the authors should drastically reduce the introduction of the article, in particular in relation to the biological activity and anticancer action mechanism of ruthenium complexes, which seems a bit out of place considering that the potential biological activity of the synthesized complexes is not studied.

Other typos need correction:

-          Page 1: The symbol of Rhodium is Rh (not Rd).

Page 1: “piano-stool structured complexes” instead of “piano structured complexes”.

-          In the abstract and section 3.2, the formulations of the precursor ruthenium dimers are not correct.

-          Page 3: Figure 1 instead of Schemes 1a-c (such schemes are not present in the manuscript).

-          C alerts appear in the checkcif reports (some of them needs clarification).

Author Response

 All comments have be responded, see attached

Author Response File: Author Response.pdf

Reviewer 2 Report

Please see the attachment.

Comments for author File: Comments.pdf

Author Response

We have revised out manuscript as advised

Reviewer 3 Report

The article by Mambanda et al is devoted to new complexes of ruthenium with para-cymene and a pyrazole-containing N^N ligand. The compounds synthesized in the work are new, the cif report files do not contain high-level errors, and the spectroscopic characterization of the substances is meticulous and comprehensive.
The work should be carefully checked for typographical errors. A number of technical notes should be taken into account before publication.
1. Page 1 line 20 "slow vaporization" - it's better to write "slow evaporation"
2. P1L33 Rhodium – Rh, not the “Rd”
3. FigS3abc The general view of the mass spectrum should be given in a small inset, and the fragment corresponding to the molecular ion should be enlarged and the calculated mass spectrum should be shown for comparison.
4. Fig S4 Ru1 and Ru2 give the impression that there is still an absorption band after 600 nm. It would be rational to bring the spectrum to a longer wavelength

Author Response

We have revised our manuscript as advised

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

 

The first revision of the manuscript is positive but there are several more issues that could be improved.

Abstract:

r. 25:  “mass spectroscopy” to be replaced by “mass spectrometry”

r. 25 and r. 228, 231 etc. “elementary analysis” to be replaced by “elemental analysis” 

Р. 354 – “(1.1 mmol equivalents)” should be replays by 1.1 mmol

There are wrong numbers of the figures, for example Fig. S14 (r 192) refers to IR spectrum of the free ligand and not to the 1H NMR resonances for the free ligand.

In general, it is necessary that all numbers of tables and figures be checked for compliance with the information contained.

Spectroscopic data:

1.      NMR – characterization. Again, the information is not full: 1) Why DMSO is used as a solvent, considering its perfect coordination ability to Ru(II) and as a consequence possibility to destroy the complexes? 2) The spectra seem similar especially Ru1 and Ru2 but also and Ru3 and this needs an additional explanation. Here I want to emphasize the distinctly different electronic effect of Cl-, Br- and I-. The bond distance: Ru-X (X= Cl-, Br- and I-) is completely different (from single-crystal data analysis) , and if they are in inner coordination sphere it should be affect that positions of the 1H- and 13C- NMR signals as well. My experience shows that the statement: "that the halide, as a weaker field ligand, cannot affect the spectroscopic data of the other coordinated ligands" is not true, because each of them has different electronic effect and this affects the overall distribution of the electron density.

2.      UV/Vis spectra presented on the figure S13 of the three complexes seem different. An additional explanation  is necessary also here: 1) It is interesting to know the concentration range of sample solutions of complexes Ru1, Ru2 and Ru3 for recording the spectra, given that they are isolated as neutral compounds after addition of C₂H₅OH- solution of NH₄BF₄, and the spectra were recorded of the compounds dissolved in CH₃OH? At the same time, the polarity of the two solvents is almost the same; 2) The interpretation of the origin of the bands needs to be thought through because it is not possible the bands that belong to π-π* electronic transitions, n-π* transition, M-to-L charge transfer to be registrated of the spectrum of the compound solution at one and the same concetration.

3.      IR spectra: 1) The sentence:  (r. 262) “The vibrational stretching bands of Ru1-3 (Fig. S15-17) shift to longer wavenumbers compared to that refer to (Fig. S14) of the free ligand, 3-chloro-6-(1H-pyrazol-1-yl)pyridazine.” is completely wrong. In any case, it should be rewritten correctly! 2) There continue to be errors in the bands assignments as well, for example: r. 447 – “2085 ?(N=Npdzn)”?; r. 432 – “2104 ?(N=Npdzn)”?; r.418 – “2104 ?(N=Npdzn)” and etc.?

4.      I believe that the spectral characteristics of the complexes are presented correctly, but their interpretation needs further rethinking. While the structure of single crystals is undisputed, the structure in solution is also affected by the nature of the solvent and processes of substitution of ligands, for example halides with solvent molecules, are possible. This can also lead to the destruction of the complexes. And this is the reason why the interpretation of the spectral features needs a deeper analysis to prove the structure in the solid state and in solution in an undisputed way.

 

 

Author Response

 See our comments attached

Author Response File: Author Response.pdf