Platinum trans‐Bis(borirene) Complexes Displaying Coplanarity and Communication Across a Platinum Metal Center

Ambient‐temperature photolysis of the aminoborylene complex [(OC)₅Cr?B?N(SiMe₃)₂] in the presence of a series of trans‐bis(alkynyl)platinum(II) precursors of the type trans‐[Pt(CCAr)₂(PEt₃)₂] (Ar=Ph, p‐C₆H₄OMe, and p‐C₆H₄CF₃) successfully leads to twofold transfer of the borylene moiety [ : B?N(SiMe₃)₂] onto the alkyne functionalities. The alkynyl precursors and resultant bis(borirene)platinum(II) complexes formed are of the type trans‐[Pt(B{?N(SiMe₃)₂}C?CAr)₂(PEt₃)₂] (Ar=Ph, p‐C₆H₄OMe, and p‐C₆H₄CF₃). These species have all been successfully characterized by NMR, IR, and UV/Vis spectroscopy as well as by elemental analysis. Single‐crystal X‐ray diffraction has verified that these trans‐bis(borirene)platinum(II) complexes display coplanarity between the twin three‐membered rings across the platinum core in the solid state and stand as the first examples of coplanar conformations of twin borirene systems. These complexes were modeled using density functional theory (DFT), providing information helpful in determining the ability of the transition metal core to interact with each individual borirene ring system and allowing for the observed coplanarity of these rings in the solid state. This proposed transition metal interaction with the twin borirene systems is manifested in the electronic characterization of these borirene species, which display divergent photophysical UV/Vis spectroscopic profiles compared to a previously published mono(borirene)platinum(II) complex.     

A Redox‐Active Dinuclear Platinum Complex Exhibiting Multicolored Electrochromism and Luminescence

A redox series of cyclometalated platinum complexes based on a dinuclear motif linked by acetamidato (aam) bridging ligands, [Pt₂(μ‐aam)₂(ppy)₂] (ppy^?=2‐phenylpyridinate ion), has been synthesized. The complexes in this series are easily oxidized and reduced by both electrochemical and chemical methods, and this is accompanied by multistep changes in their optical properties, that is, multiple color changes and luminescence. Isolation of the complexes and the structural determination of three oxidation states, +2, +2.33, and +3, have been achieved. The mixed‐valent complex, with an average oxidation state of +2.33, forms a trimer based on the dinuclear motif. The mixed‐valent complex has a characteristic color owing to intervalence transitions in the platinum chain. In contrast, the divalent complex exhibits strong red phosphorescence originating from a triplet metal‐metal‐to‐ligand charge transfer (³MMLCT) state. This study demonstrates the unique chromic behavior of a redox‐active and luminescent platinum complex.     

Synthesis and Analysis of the Structure,Diffusion and Cytotoxicity of Heterocyclic Platinum(IV) Complexes

We have developed six dihydroxidoplatinum(IV) compounds with cytotoxic potential. Each derived from active platinum(II) species, these complexes consist of a heterocyclic ligand (H_L) and ancillary ligand (A_L) in the form [Pt(H_L)(A_L)(OH)₂]²⁺, where H_L is a methyl‐functionalised variant of 1,10‐phenanthroline and A_L is the S,S or R,R isomer of 1,2‐diaminocyclohexane. NMR characterisation and X‐ray diffraction studies clearly confirmed the coordination geometry of the octahedral platinum(IV) complexes. The self‐stacking of these complexes was determined using pulsed gradient stimulated echo nuclear magnetic resonance. The self‐association behaviour of square planar platinum(II) complexes is largely dependent on concentration, whereas platinum(IV) complexes do not aggregate under the same conditions, possibly due to the presence of axial ligands. The cytotoxicity of the most active complex, exhibited in several cell lines, has been retained in the platinum(IV) form.     

Conversion of trans‐Diboran(4)yl Platinum Complexes into Their cis‐Bisboryl Analogues

The diboran(4)yl trans‐[(iPr₃P)₂Pt(Br){B(NMe₂)B(NMe₂)Br}] ( 1 ) is readily converted into its cis‐bisboryl analogues 2 and 3 by reaction with the chelating bisphosphines 1,2‐bis(dicyclohexylphosphino)ethane (dcpe) and 1,1‐bis(dicyclohexylphosphino)methane (dcpm), respectively. A plausible mechanism of this transformation consists of a sequence of reductive diborane(4) elimination and subsequent reoxidative addition of its B? B bond to the low‐valent platinum centers. Thus, the forced cis configuration of the phosphine ligands induces a change in the preferred reaction site of the diborane(4) with respect to oxidative addition. The reactions proceed with high selectivities, and the cis‐bisboryl complexes 2 and 3 were isolated in moderate yields (55 and 46 %). Moreover, their identity was clearly verified by NMR spectroscopy and X‐ray diffraction studies.     

Preparation of Dimethyl and Chloro/Methyl Complexes of Platinum(II) Supported by α‐Diimine Ligands: Trends in the Ease of Oxidation to Platinum(IV)

α‐Diimine ligands react with the platinum(II) alkyl complexes [(Me₂S)PtMe₂]₂ and (Me₂S)₂PtClMe to form (RDAB^R′)PtMe₂ and (RDAB^R′)PtClMe (RDAB^R′=RN=CR′−CR′=NR; R=2,6‐Me₂Ph, 2,6‐(CHMe₂)₂Ph, 3,5‐Me₂Ph, 3,5‐(CF₃)₂Ph, C₆H₁₁; R′=Me, H). The oxidation of these complexes with Cl₂, I₂, N‐chlorosuccinimide, [PtCl₆]²⁻ and (TMEDA)PtMe₂I₂ has been investigated. Attempts to determine the oxidation potentials of the Pt^II complexes electrochemically yielded only irreversible one‐electron oxidations. However, a qualitative ordering of increasing difficulty of oxidation has been determined for the series (RDAB^R′)PtMe₂<(RDAB^R′)PtClMe<(RDAB^R′)PtCl₂≪(RDAB^R′)PtMe(solvent)]⁺. The oxidation proceeds via a two‐electron inner‐sphere electron transfer from a bridged binuclear intermediate. The oxidation of (RDAB^R′)PtMe₂ by (TMEDA)PtMe₂I₂ exhibits characteristic third‐order kinetics, first‐order each in [Pt^II], [Pt^IV] and [I⁻]. Oxidation by a one‐electron process in MeCN solution results in a rapid subsequent disproportionation to Pt^IIMe and Pt^IVMe₃ cations with MeCN occupying the fourth or sixth coordination sites. Single‐crystal X‐ray structure determinations for [(2,6‐Me₂PhDAB^Me)PtMe₃(MeCN)]⁺[PtCl₆]_0.5(MeCN) and [(CyDAB^H)PtMe₃(MeCN)]⁺[PtCl₆]_0.5(MeCN) are reported.     

Synthesis,Structural Characterization and Reactivity of a Bis(phosphine)(silyl) Platinum(II) Complex

Treatment of 1,2‐C₆H₄(SiH₃)(SiH₃) ( 1 ) with Pt(dmpe)(PEt₃)₂ (dmpe=Me₂PCH₂CH₂PMe₂) in the ratio of 1:1 leads to the complex {1,2‐C₆H₄(SiH₂)(SiH₂)}Pt^II (dmpe) ( 2 ), which can react with proton organic reagent bearing hydroxy group with low steric hindrance to form a tetra‐alkoxy substituted silyl platinum(II) compound ( 3 ). Compounds 2 and 3 are the very rare examples of silyl transition‐metal complexes derived from this chelating hydrosilane ligand. To the best of our knowledge, there are only 6 examples of silyl metal complexes prepared from this ligand with such structural features registered in the Cambridge Structural Database, among them, only one silyl platinum(II) compound is presented. The structures of complexes 2 and 3 were unambiguously determined by multinuclear NMR spectroscopic studies and single crystal X‐ray analysis.     

Internalization of Ineffective Platinum Complex in Nanocapsules Renders It Cytotoxic

Anticancer therapy by platinum complexes, based on nanocarrier‐based delivery, may offer a new approach to improve the efficacy and tolerability of the platinum family of anticancer drugs. The original rules for the design of new anticancer platinum drugs were affected by the fact that, although cisplatin (cis‐[PtCl₂(NH₃)₂) was an anticancer drug, its isomer transplatin was not cytotoxic. For the first time, it is demonstrated that simple encapsulation of an inactive platinum compound in phospholipid bilayers transforms it into an efficient cytotoxic agent. Notably, the encapsulation of transplatin makes it possible to overcome the resistance mechanisms operating in cancer cells treated with cisplatin and prevents inactivation of transplatin in the extracellular environment. It is also shown that transplatin delivered to the cells in nanocapsules, in contrast to free (nonencapsulated) complex, forms cytotoxic cross‐links on DNA.     

Reactivity of Lewis Basic Platinum Complexes Towards Fluoroboranes

We herein report detailed investigations into the interaction of Lewis acidic fluoroboranes, for example BF₂Pf (Pf=perfluorophenyl) and BF₂Ar^F (Ar^F=3,5‐bis(trifluoromethyl)phenyl), with Lewis basic platinum complexes such as [Pt(PEt₃)₃] and [Pt(PCy₃)₂] (Cy=cyclohexyl). Two presumed Lewis adducts could be identified in solution and corresponding secondary products of these Lewis adducts were characterized in the solid state. Furthermore, the concept of frustrated Lewis pairs (FLP) was applied to the activation of ethene in the system [Pt(BPf₃)(CH₂CH₂)(dcpp)] (dcpp=1,3‐bis(dicyclohexylphosphino)propane; Pf=perfluorophenyl). Finally, DFT calculations were performed to determine the interaction between the platinum‐centered Lewis bases and the boron‐centered Lewis acids. Additionally, several possible mechanisms for the oxidative addition of the boranes BF₃, BCl_3, and BF₂Ar^F to the model complex [Pt(PMe₃)₂] are presented.     

Activation of Elemental Sulfur at a Two‐Coordinate Platinum(0) Center

Platinum dichalcogenides have been known to exhibit two‐dimensional layered structures. Herein, we describe the syntheses, isolation, and characterization of air‐stable crystalline cyclic alkyl(amino) carbene (cAAC)‐supported monomeric platinum disulfide three‐membered ring complex [(cAAC)₂Pt(S₂)] ( 2 ). The highly reactive platinum(0) [(cAAC)₂Pt] complex ( 1 ) with two‐coordinate platinum activates elemental sulfur to give 2 . The brown crystals of bis‐carbene platinum(II)monosulfate [(cAAC)₂Pt(SO₄)_x(S₂)_1?x] ( 4 ) have been isolated when the reaction was performed in air. The dioxygen analogue of 2 was formed upon exposing the THF solution of 1 to aerial oxygen (O₂). The binding of oxygen at the Pt⁰ center was found to be reversible. Additionally, DFT study has been performed to elucidate the electronic structure and bonding scenario of 2 , 3 , and 4 . Quantum chemical calculations showed donor–acceptor‐type interaction for the Pt?S bonds in 2 and Pt?O bonds in 3 and 4 .     

Immobilization of Platinum(II) and Platinum(IV) Complexes on Oxidized Nanoporous Carbon Material and Evaluation of the Enthalpy of Adsorption

Physicochemical study of cis-[Pt(NH3)2Cl2] and cis-[Pt(NH₃)₂Cl₂(OH)₂] is carried out, and immobilization of platinum complexes on the nanoporous carbon substrate is investigated. The solubility of cis-[Pt(NH₃)₂Cl₂] in 1 M HCl solution is determined, and the average enthalpy of dissolution is calculated: Δ_solH° = 27.3 ± 0.9 kJ/mol. The batch capacity is determined experimentally for cis-[Pt(NH3)2Cl2] and cis- [Pt(NH₃)₂Cl₂(OH)₂] to be 32.9 mg/g (0.17 mg-equiv/g) and 47.6 mg/g (0.24 mg-equiv/g), respectively. Immobilization of platinum complexes on the oxidized carbon surface is found to take place due to interaction between carboxy groups and ammine groups of platinum complexes. The resulting heat capacity curves are used to calculate the enthalpies of adsorption for cis-[Pt(NH₃)₂Cl₂] and cis-[Pt(NH₃)₂Cl₂(OH)₂] on the oxidized carbon surface, equal to 24.46 and 27.46 kJ/mol, respectively.     

Platinum(0) complexes of cyclopropenes

Cyclopropene and its 3-methyl, 3,3-dimethyl, 1,2-dimethyl, 1,3,3-trimethyl and 1,2,3-trimethyl derivatives have been coordinated to platinum by replacement of ethylene in Pt(C₂H₄)(PPh₃)₂. The complexes have been identified by NMR spectroscopy and X-ray analysis.     

Characteristics of the Oxidation of Carbon Monoxide on Platinum and Palladium Acetylacetonates Immobilized on a Silica Surface

Characteristics of the kinetics of the oxidation of carbon monoxide on acetylacetonates of palladium and platinum immobilized on a silica surface have been studied. The bound metal complexes show no hysteresis in the dependence of the rate of reaction on the concentration of CO and O₂ and have a higher catalytic activity than Pt/SiO₂ and Pd/SiO₂. A mechanism is proposed for the oxidation of carbon monoxide on platinum and palladium complexes bound to a SiO₂ surface.     

Platinum(II)–Gadolinium(III) Complexes as Potential Single‐Molecular Theranostic Agents for Cancer Treatment

Theranostic agents are emerging multifunctional molecules capable of simultaneous therapy and diagnosis of diseases. We found that platinum(II)–gadolinium(III) complexes with the formula [{Pt(NH₃)₂Cl}₂GdL](NO₃)₂ possess such properties. The Gd center is stable in solution and the cytoplasm, whereas the Pt centers undergo ligand substitution in cancer cells. The Pt units interact with DNA and significantly promote the cellular uptake of Gd complexes. The cytotoxicity of the Pt–Gd complexes is comparable to that of cisplatin at high concentrations (≥0.1 mM ), and their proton relaxivity is higher than that of the commercial magnetic resonance imaging (MRI) contrast agent Gd–DTPA. T₁‐weighted MRI on B6 mice demonstrated that these complexes can reveal the accumulation of platinum drugs in vivo. Their cytotoxicity and imaging capabilities make the Pt–Gd complexes promising theranostic agents for cancer treatment.     

Platinum(II) Metallomesogens: New External‐Stimuli‐Responsive Photoluminescence Materials

New dicatenar isoquinoline‐functionalized pyrazoles, [Hpz^R(n,n)iq] (R(n,n)=C₆H₃(OC_nH_2n+1)₂; n=4, 6, 8, 10, 12, 14, 16, 18), have been strategically designed and synthesized to induce mesomorphic and luminescence properties into the corresponding bis(isoquinolinylpyrazolate)platinum(II) complexes [Pt(pz^R(n,n)iq)₂]. Thermal studies reveal that all platinum(II) compounds exhibit columnar mesophases over an exceptionally wide temperature range, above 300 °C in most cases. The photophysical behavior was also investigated in solution and in the solid state. As a consequence of the formation of Pt???Pt interactions, the weak greenish emission of the platinum derivatives turns bright orange in the mesophase. Additionally, the complexes are sensitive to a great variety of external inputs, such as temperature, mechanical grinding, pressure, solvents, and vapors. On this basis, they are used as dopant agents of a polyvinylpyrrolidone or poly(methyl methacrylate) polymer matrix to achieve stimuli‐responsive thin films.     

Activation of 1, 2‐Dihydrodisilanes at Platinum(0) Phosphine Complexes: Syntheses and Structures of Bissilyl Platinum(II) Complexes

The bissilyl complexes 3 – 6 were synthesized by reactions of the platinum(0) complexes [Pt(η²‐C₂H₄)(diphos)] ( 1 : diphos = dppe; 2 : diphos = dcpe) with the disilanes 1, 1,2, 2‐tetramethyldisilane and 1, 1,2, 2‐tetraphenyldisilane via Si–Si bond activation. The molecular structures of 4 and 5 in the solid state are reported. The reaction of 2 with HPh₂SiSiPh₂H led to the immediate formation of the hydrido disilanyl complex [Pt(H)(SiPh₂SiPh₂H)(dcpe)] ( 7 ), which converts slowly into the bissilyl complex [Pt(SiHPh₂)₂(dcpe)] ( 6 ). The latter was reported before to be a η²‐disilene complex.     

Unprecedented 1D Mixed-metal Polynuclear Cyclometalated Platinum Complexes： Synthesis, Structural Characterization and Spectroscopic Properties

The complexes [Pt2L2（μ-dppm）]（ClO4）2 （1） and {[Pt2L2（μ-dppm）Li（CH3CN）2]（ClO4）3}n （2）, where HL is 6-[4-（diethoxyphosphorylmethyl）phenyl]-2,2′-bipyridinyl and dppm is bis（diphenylphosphino）methane, have been synthesized and characterized. In complex 1 the platinum（Ⅱ） center adopts a distorted square planar coordination geometry. The polymer 2 exhibits a ＂stairstep＂ configuration with one-dimensional Pt（Ⅱ）N^N^CPO- Li（Ⅰ）-OPC^N^ NPt（Ⅱ） mixed-metal units which are linked through dppm. Both complexes have metal-metal interaction with Pt- Pt distances of 3.325（2） and 3.1432（9） A, respectively, and display strong metal-metal-to-ligand charge-transfer （MMLCT） triplet state emission. The density-functional-theory calculation was used to interpret the absorption spectra of the complexes.     

The Coordination Chemistry of Pentafluorophenylphosphino Pincer Ligands to Platinum and Palladium

The synthesis of electron‐poor PCP pincer ligands 1,3‐((C₆F₅)₂PO)₂C₆H₄, 1,3‐((C₆F₅)₂PCH₂)₂C₆H₄, and 1‐((C₆F₅)₂PO)‐3‐(tBu₂PCH₂)C₆H₄, and their coordination chemistry to platinum and palladium is described. The most electron‐poor ligand 1,3‐((C₆F₅)₂PO)₂C₆H₄ (POCOPH) reacts with Group 10 metal chloride precursors to form a range of unusual cis, trans‐dimers of the type κ²‐P,P‐[(POCOPH)MCl(L)]₂ (M=Pt, Pd; L=Cl, Me), which undergo metallation to form [(POCOP)MCl] pincer complexes only under prolonged thermolysis. The formation of such cis,trans‐dimers during pincer complex formation can be mitigated through the use of starting materials with more strongly binding ancillary ligands, improving the overall rate of ligand metallation. Carbonyl complexes of the type [(PCP)M(CO)]⁺ were synthesised from the pincer chloride complexes by halide abstraction, and displayed large ν(C?O) values, from 2170–2111 cm^?1, confirming the electron‐poor nature of the compounds. The [(PCP)Pd(CO)]⁺ complexes also demonstrated the ability to reversibly bind carbon monoxide both in solution and the solid state, with the rate of decarbonylation increasing with increasing wavenumber for the C?O stretch.     

Voltammetric Study of Some Synthetic Antioxidants on Platinum Microelectrodes in Acetic Acid Medium

The electrochemical oxidation of the antioxidants tert‐butylhydroquinone (BHQ), tert‐butyl‐4‐hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) has been investigated by voltammetry at platinum microelectrodes in glacial acetic acid containing sodium perchlorate or sodium acetate as a background electrolyte. BHQ, a compound with para‐diphenyl groups, was typically found to have lower oxidation potential than isolated phenols BHA and BHT. Particular attention has been devoted to the mechanism of the electrode processes. Linear scan voltammograms recorded under steady‐state conditions showed well‐defined oxidation waves of the compounds studied even at relatively high concentrations (2 mM), due to a low proclivity for adsorption of the oxidation products on the electrode surface in acetic acid. The optimal conditions for the voltammetric determination of BHQ, BHA and BHT have also been studied. The results reveal that sensitive response for all the oxidants studied can be obtained in solution containing 0.1 M NaClO₄ and 0.1 M CH₃COONa by using the differential pulse voltammetry and square‐wave voltammetry. Peak currents were found to vary linearly with the antioxidant concentration over the range 3×10^?5?1×10^?3 M.     

Platinum (II) N‐heterocyclic carbene complexes: Synthesis,characterization and cytotoxic properties

Platinum (II) complexes bearing N‐heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry, but there are very few reports of biological properties of this type of complexes. A series of [PtCl₂(NHC)(PEt₃)] complexes were synthesized. The structures of all compounds were characterized by ¹H‐NMR, ¹³C‐NMR, IR and elemental analysis techniques, which supported the proposed structures. The single crystal structures of complexes 1a and 1e were determined. The title complexes show slightly distorted square‐planar coordination around the platinum (II) metal center. The cytotoxic properties of the platinum (II)–NHC complexes have been assessed in various human cancer lines, including cisplatin‐sensitive and resistant cells. IC₅₀ values of these four complexes were determined by the MTS‐based assay on three human cell lines—brain (SHSY5Y), colon (HTC116) and liver (HEP3B). These complexes have been highlighted cancer therapeutic agent with unique structures and functions.