Discovery of Polythioplatinate(II) [Pt3S2(SO3)6]10- and Study of Its Solution and Catalytic Properties.

We have discovered the first polythioplatinate(II), [PtII3S2(SO3)6]10- (1), which was synthesized in aqueous basic medium (pH 11) by hydrothermal heating at 150 °C. Polyanion 1 comprises a discrete, triangular assembly of three Pt2+ ions linked by two µ3-sulfido ligands, and their square-planar coordination geometry is completed by two terminal S-bound sulfito ligands. Polyanion 1 was isolated as a hydrated sodium salt, Na10[PtII3(µ3-S)2(SO3)6]·22H2O (Na-1), which was characterized in the solid state by single-crystal X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectra, and elemental analysis, in solution by 195Pt NMR and atomic absorption spectroscopy, and in the gas phase by electrospray ionization mass spectrometry. Density functional theory calculations were performed, and the 195Pt NMR chemical shifts of 1 were computed theoretically and shown to match well with the experimental data. Furthermore, the discrete title polyanion 1 was immobilized on mesoporous SBA-15 support and used as a precatalyst for the hydrogenation of o-xylene.

Organorhodium(III)- and Iridium(III)-Substituted 20-Tungstobismuthates(III) and -Antimonates(III), [(MCp*)2X2W20O70]10- (M = RhIII and IrIII; X = BiIII and SbIII).

The synthesis of four organometallic RhCp*- and IrCp*-containing heteropoly-20-tungstates, [{RhCp*}2Bi2W20O70]10- (1), [{IrCp*}2Bi2W20O70]10- (2), [{RhCp*}2Sb2W20O70]10- (3), and [{IrCp*}2Sb2W20O70]10- (4) has been accomplished by reaction of (MCp*Cl2)2 with [X2W22O74(OH)2]12- in aqueous solution at pH 6 and 70 °C. The four polyanions 1-4 were structurally characterized in the solid state by single-crystal XRD, FTIR, and TGA and in solution by 183W and 13C NMR. For the Rh derivatives 1 and 3 the 183W-103Rh coupling (2 J W-Rh 3.0 Hz) could be identified by 183W NMR.

Metallodrug Profiling against SARS-CoV-2 Target Proteins Identifies Highly Potent Inhibitors of the S/ACE2 interaction and the Papain-like Protease PLpro.

The global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has called for an urgent need for dedicated antiviral therapeutics. Metal complexes are commonly underrepresented in compound libraries that are used for screening in drug discovery campaigns, however, there is growing evidence for their role in medicinal chemistry. Based on previous results, we have selected more than 100 structurally diverse metal complexes for profiling as inhibitors of two relevant SARS-CoV-2 replication mechanisms, namely the interaction of the spike (S) protein with the ACE2 receptor and the papain-like protease PLpro . In addition to many well-established types of mononuclear experimental metallodrugs, the pool of compounds tested was extended to approved metal-based therapeutics such as silver sulfadiazine and thiomersal, as well as polyoxometalates (POMs). Among the mononuclear metal complexes, only a small number of active inhibitors of the S/ACE2 interaction was identified, with titanocene dichloride as the only strong inhibitor. However, among the gold and silver containing complexes many turned out to be very potent inhibitors of PLpro activity. Highly promising activity against both targets was noted for many POMs. Selected complexes were evaluated in antiviral SARS-CoV-2 assays confirming activity for gold complexes with N-heterocyclic carbene (NHC) or dithiocarbamato ligands, a silver NHC complex, titanocene dichloride as well as a POM compound. These studies might provide starting points for the design of metal-based SARS-CoV-2 antiviral agents.

NiII 36 -Containing 54-Tungsto-6-Silicate: Synthesis, Structure, Magnetic and Electrochemical Studies.

The 36-NiII -containing 54-tungsto-6-silicate, [Ni36 (OH)18 (H2 O)36 (SiW9 O34 )6 ]6- (Ni36 ) was synthesized by a simple one-pot reaction of the Ni2 -pivalate complex [Ni2 (µ-OH2 )(O2 CCMe3 )4 (HO2 CCMe3 )4 ] with the trilacunary [SiW9 O34 ]10- polyanion precursor in water and structurally characterized by a multitude of physicochemical techniques including single-crystal XRD, FTIR, TGA, elemental analysis, magnetic and electrochemical studies. Polyanion Ni36 comprises six equivalent {NiII 6 SiW9 } units which are linked by Ni-O-W bridges forming a macrocyclic assembly. Magnetic studies demonstrate that the {Ni6 } building blocks in Ni36 remain magnetically intact while forming a hexagonal ring with antiferromagnetic exchange interactions between adjacent {Ni6 } units. Electrochemical studies indicate that the first reduction is reversible and associated with the WVI/V couple, whereas the second reduction is irreversible attributed to the NiII/0 couple.

PtIV- or MoVI-substituted decavanadates inhibit the growth of Mycobacterium smegmatis.

Inhibitory effects of two monosubstituted decavanadates by PtIV in monoplatino(IV)nonavanadate(V) ([H2PtIVV9O28]5-, V9Pt), and by MoIV in monomolybdo(VI)nonavanadate(V) ([MoVIV9O28]5-,V9Mo) were investigated against the growth of Mycobacterium smegmatis with the EC50 values of 0.0048 mM and 0.015 mM, respectively. These compare to the reported inhibitory value for decavanadate ([V10O28]6-/[HV10O28]5-, V10) on Mycobacterium smegmatis (EC50 = 0.0037 mM). Time-dependent 51V NMR spectroscopic studies were carried out for all three polyanions in aqueous solution, biological medium (7H9), heated and non-heated supernatant to evaluate their stability in their respective media, monitor their hydrolysis to form various oxovanadates over time and calculate the EC50 values. These studies allow us to calculate adjusted and maximum EC50 for the polyoxovanadate (POV) present in solution at the beginning of the study when there is most intact anion in the media and thus the EC50 values represent the initial effects of the POVs. The results have shown that V10 is 1.3 times more potent than V9Pt and 4 times more potent than V9Mo, indicating that the inhibitory effects of monosubstituted polyanions are related to the V10 structure. We attributed the minor differences in the growth inhibitory effects to the differences in charges (5- vs 6-) of V9Pt and V9Mo compared to V10 and/or the differences in the chemical composition. We concluded that the potency of the growth inhibition by V10 is mainly due to the chemical properties of the vanadium and the decametalate's unique structure even though the presence of the Mycobacterium smegmatis facilitate hydrolysis of the anions. SYNOPSIS: Two decavanadate derivatives, monoplatino(IV)nonavanadate(V) ([H2PtIVV9O28]5-), monomolybdo(VI)nonavanadate(V) ([MoVIV9O28]5-) and decavanadate are more potent growth inhibitors of Mycobacterium smegmatis than monomeric vanadate. The spectroscopic characterization carried out in the growth medium led to the conclusion that both the decavanadate structure and its properties are important for its growth effects.

Palladium(II)-Containing Tungstoarsenate(V), [PdII4(As2W15O56)2]16-, and Its Catalytic Properties.

We have synthesized and structurally characterized the 4-palladium(II)-containing 30-tungsto-4-arsenate(V), [Pd4(As2W15O56)2]16- (1), which represents the first palladium(II)-containing tungstoarsenate(V). The title polyanion 1 was prepared by a simple one-pot procedure in aqueous medium and characterized by single-crystal X-ray diffraction (XRD), thermogravimetric analysis (TGA), cyclic voltammetry, elemental analysis, and 183W nuclear magnetic resonance (NMR), infrared (IR), and ultraviolet-visible (UV-vis) spectroscopies. Polyanion 1 consists of four Pd2+ ions that are coordinated in a square-planar geometry to two trilacunary [As2W15O56]12- Wells-Dawson fragments resulting in a sandwich-type assembly. Catalytic studies on 1 revealed that it is an efficient catalyst precursor for the Suzuki-Miyaura cross-coupling reactions of various aryl halides in aqueous and nonaqueous media.