Square-Planar PtIIversus Octahedral PtIVHalido Complexes:195Pt NMR Explained by a Simple Empirical Approach

Platinum-Nucleos(t)ide Compounds as Possible Antimetabolites for Antitumor/Antiviral Therapy: Properties and Perspectives

Nucleoside analogues (NAs) are a family of compounds which include a variety of purine and pyrimidine derivatives, widely used as anticancer and antiviral agents. For their ability to compete with physiological nucleosides, NAs act as antimetabolites exerting their activity by interfering with the synthesis of nucleic acids. Much progress in the comprehension of their molecular mechanisms has been made, including providing new strategies for potentiating anticancer/antiviral activity. Among these strategies, new platinum-NAs showing a good potential to improve the therapeutic indices of NAs have been synthesized and studied. This short review aims to describe the properties and future perspectives of platinum-NAs, proposing these complexes as a new class of antimetabolites.

Predicting 195 Pt NMR Chemical Shifts in Water-Soluble Inorganic/Organometallic Complexes with a Fast and Simple Protocol Combining Semiempirical Modeling and Machine Learning

Water-soluble Pt complexes are the key components in medicinal chemistry and catalysis. The well-known cisplatin family of anticancer drugs and industrial hydrosylilation catalysts are two leading examples. On the molecular level, the activity mechanisms of such complexes mostly involve changes in the Pt coordination sphere. Using ¹⁹⁵ Pt NMR spectroscopy for operando monitoring would be a valuable tool for uncovering the activity mechanisms; however, reliable approaches for the rapid correlation of Pt complex structure with ¹⁹⁵ Pt chemical shifts are very challenging and not available for everyday research practice. While NMR shielding is a response property, molecular 3D structure determines NMR spectra, as widely known, which allows us to build up 3D structure to ¹⁹⁵ Pt chemical shift correlations. Accordingly, we present a new workflow for the determination of lowest-energy configurational/conformational isomers based on the GFN2-xTB semiempirical method and prediction of corresponding chemical shifts with a Machine Learning (ML) model tuned for Pt complexes. The workflow was designed for the prediction of ¹⁹⁵ Pt chemical shifts of water-soluble Pt(II) and Pt(IV) anionic, neutral, and cationic complexes with halide, NO₂ ^- , (di)amino, and (di)carboxylate ligands with chemical shift values ranging from -6293 to 7090 ppm. The model offered an accuracy (normalized root-mean-square deviation/RMSD) of 1.08 %/145.02 ppm on the held-out test set.

Is hydrogen electronegativity higher than Pauling’s value? New clues from the13C and29Si NMR chemical shifts of [CHF3] and [SiHF3] molecules

We previously demonstrated that the δ NMR chemical shift of central NMR active atoms (A), in simple halido [AXn] (A=C, Si, Ge, Sn, Pb, Pt; Xn = combination of n halides, n = 4 or 6) derivatives, could be directly related to X radii overall sum, Σ(rL). Further correlation have also been observed for tetrahedral [AX4] (A=C, Si; X4 = combination of four halides) compounds where the X Pauling electronegativities sum,Σ(χLPau),$\Sigma (\chi _L^{{\rm{Pau}}}),$exceeds a specific value (≈12.4). In this work, we focused on these latter systems considering the H vs. X substitution. The analysis of the literature reported δ(13C) and δ(29Si) NMR chemical shift for the mono hydrogenated derivatives and in particular for [CHF3] and [SiHF3], characterized by the lowest Σ(rL) and the highestΣ(χLPau),$\Sigma (\chi _L^{{\rm{Pau}}}),$suggests a revised value for the H electronegativity ranking with respect to Pauling’s.

Insertion of terminal alkyne into Pt-N bond of the square planar [PtI2(Me2phen)] complex

The reactivity of [PtX₂(Me₂phen)] complexes (X = Cl, Br, I; Me₂phen = 2,9-dimethyl-1,10-phenanthroline) with terminal alkynes has been investigated. Although the dichlorido species [PtCl₂(Me₂phen)] exhibits negligible reactivity, the bromido and iodido derivatives lead in short time to the formation of five-coordinate Pt(ii) complexes of the type [PtX₂(Me₂phen)(η²-CH[triple bond, length as m-dash]CR)] (X = Br, I; R = Ph, n-Bu), in equilibrium with the starting reagents. Similar to analogous complexes with simple acetylene, the five coordinate species can also undergo dissociation of an halido ligand and formation of the transient square-planar cationic species [PtX(Me₂phen)(η²-CH[triple bond, length as m-dash]CR)]⁺. This latter can further evolve to give an unusual, sparingly soluble square planar product where the former terminal alkyne is converted into a :C[double bond, length as m-dash]C(H)(R) moiety with the α-carbon bridging the Pt(ii) core with one of the two N-donors of coordinated Me₂phen. The final product [PtX₂{κ²-N,C-(Z)-N[combining low line]1-N10-C[combining low line][double bond, length as m-dash]C(H)(R)}] (N1-N10 = 2,9-dimethyl-1,10-phenanthroline; X = Br, I) contains a Pt-N-C-C-N-C six-membered chelate ring in a square planar Pt(ii) coordination environment.

73Ge, 119Sn and 207Pb: general cooperative effects of single atom ligands on the NMR signals observed in tetrahedral [MXnY4-n] (M = Ge, Sn, Pb; 1 ≤ n ≤ 4; X, Y = Cl, Br, I) coordination compounds of heavier XIV group elements

An inverse linear relationship between ⁷³Ge, ¹¹⁹Sn and ²⁰⁷Pb NMR chemical shifts and the overall sum of ionic radii of coordinated halido ligands has been discovered in tetrahedral [MX_nY_4-n] (M = Ge, Sn, Pb; 1 ≤ n ≤ 4; X, Y = Cl, Br, I) coordination compounds. This finding is consistent with a previously reported correlation found in octahedral, pentacoordinate and square planar platinum complexes. The effect of the coordinated halido ligands acting on the metal as shielding conducting rings is therefore confirmed also by ⁷³Ge, ¹¹⁹Sn and ²⁰⁷Pb NMR spectroscopy.

NMR effective radius of hydrogen in XIV group hydrides evaluated by NMR spectroscopy

In the [ABr_nI_m] (A = C, Si, Ge, Sn; n + m = 4) compounds, with the heavier halido ligands bonded to the central IV group elements, the ¹³C, ²⁹Si, ⁷³Ge and ¹¹⁹Sn NMR chemical shifts were found to be linearly related to the bonded halides ionic radii overall sum, ∑(r_h). The ²⁰⁷Pb NMR chemical shift of the unstable [PbH₄] hydride could be calculated.

Synthesis, reactivity and characterization of Pt(ii) complexes with N,N′ chelating ligands; structure and dimethylsulfoxide reactivity relationship

Chelated N-heterocycles can be replaced from the coordination sphere of square planar Pt(ii) complexes by DMSO.