Peer review of: A family of lead clusters with precious metal cores (2020)

REVIEWER COMMENTS

Reviewer #1 (Remarks to the Author): 

The compounds reported in this manuscripts I find spectacular and fully deserving to be published in this 
journal. The results are very novel including the Au- and Ag-centered eleven-atom nido species in the 
Pb-group, the gold cores, and the overall aggregation of such species. The synthesis and characterization 
are very well carried out and their rationalization based on electronic structure and bonding is well 
explained. Having said this, I have one major criticism and one major technical issue. 
1) In the introduction, the authors discussed the new species almost exclusively in the context of the 
known and popular nowadays gold-thiolate clusters. This maybe OK as a sales pitch, but the reported 
clusters are clearly far from having anything in common with these know species, they are not in their 
family. At the same time, there is not much discussion about the relation to the other Zintl ions in the 
Pb-group and their stabilization by transition metals, both endohedrally and as part of the cluster 
surface, e.g. various naked and substituted Sn and Ge clusters stabilized with Pd, Ni, Pt. The new species 
clearly belong to this family and should be presented also in that context. I suggest the authors reduce 
significantly the gold-thiolate cluster talk and add more discussion on the related Zintl ions (not just Pb-
based!). 
2) The technical issue concerns [Au@AuPb11](2-). For simplicity we can assume gold to be a main-group 
element with one electron (nothing changes if we work with two gold atoms each with 11 electrons). It 
is well established that an icosahedron, a closo-cluster, requires 4n+2 valence electrons where n = 12, 
and this comes to 4 x 12 + 2 = 50. However, the number of electrons available from [Au@AuPb11](2-) is 
2 x 1 (from Au) + 11 x 4 (from Pb) + 2 (from charge) = 48, or two electrons short. The reason for this 
deviation needs to be explained in detail in the manuscript with specific focus on the orbital that 
becomes empty in [Au@AuPb11](2-) and the specific reason for that compared to normal icosahedron. 
It should be pointed out that, at the same time, the nido-species Ag@Pb11 has the correct charge of 3- 
following the standard electron counting rules. 



Reviewer #2 (Remarks to the Author): 

This manuscript describes the synthesis and structures of exciting new Ag-Pb and Au-Pb clusters that 
demonstrate new bonding motifs and structure types. The compounds are characterized through X-ray, 
DFT and some MS experiments. These large intermetalloid clusters are on the interface of molecular and 
nanoscience. I recommend publication in Nature Commun. after minor revisions. 

My only major concern is that there is a lot of speculation about structures from partial crystal 
structures and mass spec fragments. I think much of this speculation, and the partial crystal structure, 
could be removed and the paper would be much more cohesive. 

Some specific questions: 
1. How do the authors know that Au and Pb segregate? Chemically it makes chemical sense but it is 
virtually impossible to distinguish Pb from Au by X-ray. 

2. Ag@Pb11 is a nido cluster. The Au@Pb11Au icosahedra are not nido. They are 24 electron hyper-
closo by my count. There might be a nido Au@Pb11 cluster involved in the synthesis but the skeletal 
electron count of the observed fragments should be specified. 

3. I’m not sure I see how the Au@Pb11 ligands would be “tripodal”. They are bound eta-5 to the Au 
atoms of the gold cores. This should be clarified. 

4. Au12Pb44 should be subject to a Jahn Teller distortion. Do the authors have any thoughts on this? 

5. References: There have been some exciting new Au clusters out of Germany (Tubingen) that might be 
included in the discussion since they are quite relevant to the compounds at hand. Also, the series of 
M@Pb12 clusters (Co, Rh, Ir) has recently appeared in Chem. Eur. J. and should be included.