DATASET A low-coordinate platinum(0)-germylene for E-H bond activation and catalytic hydrodehalogenation

This file contains all reviewer reports in order by version, followed by all author rebuttals in order by version. Version 0: Reviewer comments: Reviewer #1 (Remarks to the Author) The manuscript entitled “An Exceedingly Low-Coordinate Platinum(0)-Germylene for E–H Bond Activation and Catalytic Hydrodehalogenation” by Jesús Campos describes the E‒H bond activation facilitated by Platinum(0)-Germylene cooperation, resulting in the formation of Pt(II)-germyl compounds. The Pt/Ge complex 1 reacts with alkynes to form 1,2platinogermacyclobutadiene compounds (compound 7), which also serve as efficient catalysts in hydrodehalogenation reactions. The structural symmetry of these compounds has been analyzed using NMR, X-ray single crystal data, and computational studies. Overall, the chemistry is well-executed and well-described, with some improvements suggested below. I am pleased to support its acceptance in this journal. General Comments: Compound 1 has successfully catalyzed the dehalogenation reaction. Can the stoichiometric reaction product of 1 with aliphatic or aromatic halides be obtained? This might help in understanding the reaction mechanism better. The authors have investigated the catalytic potential of compound 1 in the hydrodehalogenation of aliphatic and aromatic halides. What about the hydrodefluorination of organic fluorides? All yields of reactions are reported in spectroscopic form and were performed at room temperature. Can the authors attempt to separate and purify the products at low temperature to confirm the actual isolation yield of each reaction? Page 4, Line 9: “consistent with reactivity studies …” needs correction. Page 6, Figure 4: States 5 equivalents of methanol. Supplementary Information S7, Compound 4: States 2 equivalents and 1 equivalent of methanol. The authors need further confirmation and correction. Page 5, Line 10: “[ArDippGeCl]2 reacts with water, methanol, and ammonia to yield mixtures of products.” The structural information of these mixtures is not provided. Page 8, Line 12: The structural formula “κ1 interaction” of compound 3 is not consistent with “the π-interaction with the flanking aryl ring is now closer to a κ2-coordination”. Page 12, Figure 9: Change “RCCH” on the arrow to “2 RCCH”. Reviewer #2 (Remarks to the Author) The manuscript by Campos and colleagues describes an intriguing Pt germylene species (1) which was prepared by substitution of tBu-ethylene with a germylene source (a germylene dimer). Unfortunately, complex 1 is thermally unstable, and accordingly, was not isolated as an analytically pure material, nor was it characterized by X-ray crystallography. When generated in situ, complex 1 reacts with bonds in various small molecules (including the N-H of NH3). The authors refer to this as "cooperative activation", though addition of bonds across metal-main group multiple bonds is well known and usually not described as cooperative activation. Related work by Tilley (e.g. Organometallics 2009 5082) was not referenced. Complex 1 also inserts alkynes into the Pt=Ge bond. While these complexes and related reaction chemistry are interesting, they are not particularly novel. The highest impact of this work, in my opinion, is the catalytic dehydrohalogenation, particularly the fact that alkyl substrates were used. In addition, chlorides worked reasonably well. The manuscript would benefit from additional computational work to elucidate the mechanism of the catalytic cycle. If that were included, I would support publication of this manuscript in Nature Chemistry. One final comment: the authors refer to complex 1 as "exceedingly low coordinate". Given that no X-ray crystal structure was obtained, and the aryl groups on both the P and Gemight interact with the metal centre, this is perhaps somewhat of an over-reach. Why not simply call it "low coordinate"? Reviewer #3 (Remarks to the Author) This manuscript by Campos and coworkers deals with a Pt(0)-germylene complex. It is coordinately unsaturated at both Pt and Ge, which makes it proned to E-H bond activation. H2, H2O, MeOH and NH3 are shown to readily add across the formal Pt=Ge linkage. Catalytic hydrodehalogenation is also reported, with both alkyl and aryl substrates. This is a very important and original piece of work. Small molecule activation by transition metal / main group compounds has several precedents and is no longer a big surprise, but applying such systems to synthetically useful catalytic transformations is rare and remarkable. All the more so that the Pt(0)-germylene complex works with alkyl and aryl substrates with H2 as reductant. The manuscript is pleasant to read, the work is of high scientific and technic quality. All compounds have been fully characterized. I for sure recommend publication of this work in Nature Communications but there is one point that requires consideration and should be addressed before publication. It is the link between the stoechiometric studies of E-H bond activation and the catalytic hydrodehalogenation. I agree with the authors that « a thorough mechanistic picture lies out of the scope of the present contribution », but the relevance of the cooperative activation of H2 by the Pt(0)-germylene complex to the catalytic transformation should be substantiated. All the more so that the authors point some observations suggesting the involvement of radical pathways. It would also be nice to extend the stoechiometric studies to the RX substrates as some of them may compete with H2 upon reaction with the Pt(0)-germylene complex. Minor corrections : - Some phrasings are inappropriate and require polishing. For example on page 4 : « … suggesting that this atom partly retains its Z-type character ». - I also recommend careful proofreading. I noticed several typos. Version 1: Reviewer comments: Reviewer #1 (Remarks to the Author) The authors have systematically introduced the E‒H bond activation and catalytic hydrodehalogenation applications of lowcoordinate platinum(0)-germylene, elucidating the catalytic reaction mechanism through detailed experimental and theoretical calculations. The authors have also addressed my questions regarding this work, and the manuscript has been thoroughly revised and is now suitable for acceptance. Reviewer #2 (Remarks to the Author) After carefully scrutinizing the revised version of the manuscript by Campos and colleagues, as well as the responses to all reviewer comments, I fully endorse its publication in Nature Communications. Every single comment was addressed in depth and a great deal of additional work was performed. The result is substantial improvement to an already excellent contribution. Reviewer #3 (Remarks to the Author) The authors have carefully revised their manuscript. They have taken into account and convincingly addressed all the comments raised by the reviewers. In my opinion, the paper can be published in Nature Communications as is.