Is 2.07 Å a Record for the Shortest Pt−S Distance? Revision of Two Reported X-ray Structures

Abstract

The comparison of the very similar compounds (Ph(3)P)(2)Pt(mu-S)(2)Pt(PPh(3))(2) (1) and (Ph(2)PyP)(2)Pt(mu-S)(2)Pt(PPh(2)Py)(2) (2) raises intriguing questions about the reliability of the reported Pt(2)S(2) core in 1, where the Pt-S bonds are the shortest ever reported. Also, the trans-annular S...S separation of 2.69 A is surprisingly shorter in 1 than in 2 (3.01 A), but no incipient coupling between two S(2-) bridges seems reasonable in this case. Various considerations lead to reformulate 1 as [(Ph(3)P)(2)Pt(mu-OH)(2)Pt(PPh(3))(2)](BF(4))(2), 3. The sets of cell parameters for 1 and 3 are not equal but two axes match, and the volume of 1 is exactly double. Simple matrices may be constructed to interconvert the direct and reciprocal crystalline cells, thus corroborating their identity of the compounds. It is concluded that, in the structure solution of 1, some atoms were either neglected (BF(4)(-) counterions) or ill identified (sulfido in place of hydroxo bridges), while the structure of 3 was solved by collecting only one-half of the possible reflections (hence, also the different space groups). A new preparation, crystallization and X-ray structure of 3 confirms the above points and dismisses any other theoretical conjecture about two electronically different Pt(2)S(2) cores in 1 and 2.

Mass Spectrometry Evidence for Cisplatin As a Protein Cross-Linking Reagent

“…In the example of cisplatin cross-linking calmodulin, the spatial distances between the thioether sulfurs of Met109, Met124, Met144, and Met145 were based on the NMR structure of apo-calmodulin (Figure 4, the S atom of Met145 was chosen as the center, only amino acid residues within 8 Å are shown) 49 and range from 4.50 to 11.31 Å. On the basis of the literature for small platinum compounds, 50 the average PtÀS bond length is 2.318 Å; thus, the maximum spacer arm length of SÀPtÀS is around 4.63 Å, which fits the spatial distance between Met109 and Met145 (4.54 Å). Therefore, it is likely that platinum can readily trans-cross-link Met109 and Met145.…”

A Bonding Quandary—or—A Demonstration of the Fact That Scientists Are Not Born With Logic

“…Santiago carried out such an analysis on compound A, find- 7 In our published paper, reproduced above, we used a [(Ph 3 P) 4 Pt 2 S 2 ] model, [27] and reported 65% for the s* population. Subsequently, we realized that there are serious problems with the correctness of this reported structure [28] which is why we switched here to a different model. 8 In our published paper, we wrote 33%.…”

Innovation in Cross-Linking Mass Spectrometry Workflows: Toward a Comprehensive, Flexible, and Customizable Data Analysis Platform

“…Third, platinum­(II) has a binding strong affinity toward sulfur, nitrogen, and oxygen containing ligands, thereby, platinum­(II)-based compounds can react with many different types of amino acids (such as Met, His, Cys, Asp, Arg, Lys, and Glu), as well as nucleobases to enhance structural information richness . Fourth, the spacer arm length of cisplatin is between ∼2 and ∼4.5 Å , which can provide high-resolution results. In addition, the arm length can be extended by developing multinuclear platinum compounds (Figure A).…”