Die Ammonolyse von Halogenokomplexen des vierwertigen Platins

Ammonolysis of Halogeno Complexes of Tetravalent Platinum Reactions of liquid ammonia and ammonium hexahalogenoplatinates(IV) at ?40°C yield mixtures of halogenoammine complexes [Pt(NH₃)_6?nX_n]X_4?n (X = Cl, Br, I; n = 3, 2, 1, 0). Hexaammine platinum(IV) salts, [Pt(NH₃)₆]X₄, may be isolated as main product only after several weeks of reaction. Interactions at room temperature of liquid ammonia and hexachloro or hexabromo complexes produce quantitatively the novel dinuclear di-m?-amido-bis[tetraammineplatinum(IV)] complex, [(H₃N)₄Pt(NH₂)₂Pt(NH₃)₄]X₆. By interaction of gaseous or liquid ammonia and subsequent addition of potassium amide solution in excess potassium hexaamido platinate(IV), K₂[Pt(NH₂)₆], is formed in good yield.     

Studies on the reactions of bis(acetylacetonato)platinum(II) with lewis bases : IV. Preparations and characterization of novel acetylacetonato complexes [Pt(C5H6O2)L2]

Novel complexes [Pt(C₅H₆O₂)L₂] (IVa, L = PPh₃; IVb, L = PMePh₂, IVc, L = PMe₂Ph) were prepared by the reactions of [Pt(acac)₂] with tertiary phosphines either at elevated temperature (when L = PPh₃) or at room temperature (L = PMePh₂ and PMe₂Ph), whereas AsPh₃ yielded [Pt(acac)(γ-acac)AsPh₃] (Id) by the reaction with [Pt(acac)₂] even under rigorous conditions. Complexes IV were characterized on the basis of their IR and NMR spectra, elemental analyses and chemical reactions, and a structure which possesses a chelate type “acetylacetonato” ligand involving π-oxoallyl bonding is proposed.     

Zum nukleophilen Abbau von Tris(pentasulfido)platinat(IV), [Pt(S5)3]2−, und Bis(pentasulfido)platinat(II),[Pt(S5)2]2−

On the Nucleophilic Degradation of Tris(pentasulfido)platinum(IV), [Pt(S₅)₃]^2?, and Bis(pentasulfido)platinum(II), [Pt(S₅)₂]^2? The behaviour of [Pt(S₅)₃]^2?, ( I ), towards sulfite, arsenite, sulfide, hydroxide, and triphenylphosphine has been studied qualitatively and quantitatively. With stoichiometric amounts of nucleophile one ring is degraded; the reaction product [Pt(S₅)₂]^2?, ( II ), can be isolated. With excess of nucleophile all sulfur atoms are taken off from the platinum; with triphenylphosphine, however, (PPh₃)₂PtS₄, ( III ), is formed. A mechanistic interpretation of the course of the reaction is given and supported by kinetic studies.     

Oxidative addition of asparagusic acid based disulfides to Pt

[Pt(PPh₃)₄] reacts smoothly and swiftly at room temperature with asparagusic acid and with selected amide and ester derivatives of this cyclic disulfide to afford Pt^II dithiolate chelates of the type cis-[Pt{CRR′(CH₂S)₂}(PPh₃)₂]. The crystal structures of three such products are reported.     

Prediction of 195Pt NMR chemical shifts of dissolution products of H2[Pt(OH)6] in nitric acid solutions by DFT methods: how important are the counter‐ion effects?

¹⁹⁵Pt NMR chemical shifts of octahedral Pt(IV) complexes with general formula [Pt(NO₃)_n(OH)_{6 ? n}]^2?, [Pt(NO₃)_n(OH₂)_{6 ? n}]^{4 ? n} (n = 1–6), and [Pt(NO₃)_{6 ? n ? m}(OH)_m(OH₂)_n]^{?2 + n ? m} formed by dissolution of platinic acid, H₂[Pt(OH)₆], in aqueous nitric acid solutions are calculated employing density functional theory methods. Particularly, the gauge‐including atomic orbitals (GIAO)‐PBE0/segmented all‐electron relativistically contracted–zeroth‐order regular approximation (SARC–ZORA)(Pt) ∪ 6–31G(d,p)(E)/Polarizable Continuum Model computational protocol performs the best. Excellent second‐order polynomial plots of δ_calcd(¹⁹⁵Pt) versus δ_exptl(¹⁹⁵Pt) chemical shifts and δ_calcd(¹⁹⁵Pt) versus the natural atomic charge Q_Pt are obtained. Despite of neglecting relativistic and spin orbit effects the good agreement of the calculated δ ¹⁹⁵Pt chemical shifts with experimental values is probably because of the fact that the contribution of relativistic and spin orbit effects to computed σ^{iso 195}Pt magnetic shielding of Pt(IV) coordination compounds is effectively cancelled in the computed δ ¹⁹⁵Pt chemical shifts, because the relativistic corrections are expected to be similar in the complexes and the proper reference standard used. To probe the counter‐ion effects on the ¹⁹⁵Pt NMR chemical shifts of the anionic [Pt(NO₃)_n(OH)_{6 ? n}]^2? and cationic [Pt(NO₃)_n(OH₂)_{6 ? n}]^{4 ? n} (n = 0–3) complexes we calculated the ¹⁹⁵Pt NMR chemical shifts of the neutral (PyH)₂[Pt(NO₃)_n(OH)_{6 ? n}] (n = 1–6; PyH = pyridinium cation, C₅H₅NH⁺) and [Pt(NO₃)_n(H₂O)_{6 ? n}](NO₃)_{4 ? n} (n = 0–3) complexes. Counter‐anion effects are very important for the accurate prediction of the ¹⁹⁵Pt NMR chemical shifts of the cationic [Pt(NO₃)_n(OH₂)_{6 ? n}]^{4 ? n} complexes, while counter‐cation effects are less important for the anionic [Pt(NO₃)_n(OH)_{6 ? n}]^2? complexes. The simple computational protocol is easily implemented even by synthetic chemists in platinum coordination chemistry that dispose limited software availability, or locally existing routines and knowhow. Copyright © 2016 John Wiley & Sons, Ltd.     

Accurate prediction of 195Pt-NMR chemical shifts for hydrolysis products of [PtCl6]2− in acidic and alkaline aqueous solutions by non-relativistic DFT computational protocols

The ¹⁹⁵Pt-NMR chemical shifts of all possible hydrolysis products of [PtCl₆]^2? in acidic and alkaline aqueous solutions are calculated employing simple non-relativistic density functional theory computational protocols. Particularly, the GIAO-PBE0/SARC-ZORA(Pt) ∪ 6-31 + G(d)(E) computational protocol augmented with the universal continuum solvation model (SMD) performs the best for calculation of the ¹⁹⁵Pt-NMR chemical shifts of the Pt(IV) complexes existing in acidic and alkaline aqueous solutions of [PtCl₆]^2?. Excellent linear plots of δ_calcd(¹⁹⁵Pt) chemical shifts versus δ_exptl(¹⁹⁵Pt) chemical shifts and δ_calcd(¹⁹⁵Pt) versus the natural atomic charge Q_Pt are obtained. Very small changes in the Pt–Cl and Pt–O bond distances of the octahedral [PtCl₆]^2?, [Pt(OH)₆]^2?, and [Pt(OH₂)₆]⁴⁺ complexes have significant influence on the computed σ^{iso 195}Pt magnetic shielding tensor elements of the anionic [PtCl₆]^2? and the computed δ ¹⁹⁵Pt chemical shifts of [Pt(OH)₆]^2? and [Pt(OH₂)₆]⁴⁺. An increase of the Pt–Cl and Pt–O bond distances by 0.001 Å (1 mÅ) is accompanied by a downfield shift increment of 17.0, 19.4, and 37.6 ppm mÅ^?1, respectively. Counter-anion effects in the case of the highly positive charged complexes drastically improve the accuracy of the calculated ¹⁹⁵Pt chemical shifts providing values very close to the experimental ones.     

Highly trifluoromethylated platinum compounds

The homoleptic, square‐planar organoplatinum(II) compound [NBu₄]₂[Pt(CF₃)₄] ( 1 ) undergoes oxidative addition of CF₃I under mild conditions to give rise to the octahedral organoplatinum(IV) complex [NBu₄]₂[Pt(CF₃)₅I] ( 2 ). This highly trifluoromethylated species reacts with Ag⁺ salts of weakly coordinating anions in Me₂CO under a wet‐air stream to afford the aquo derivative [NBu₄][Pt(CF₃)₅(OH₂)] ( 4 ) in around 75 % yield. When the reaction of 2 with the same Ag⁺ salts is carried out in MeCN, the solvento compound [NBu₄][Pt(CF₃)₅(NCMe)] ( 5 ) is obtained in around 80 % yield. The aquo ligand in 4 as well as the MeCN ligand in 5 are labile and can be cleanly replaced by neutral and anionic ligands to furnish a series of pentakis(trifluoromethyl)platinate(IV) compounds with formulae [NBu₄][Pt(CF₃)₅(L)] (L=CO ( 6 ), pyridine (py; 7 ), tetrahydrothiophene (tht; 8 )) and [NBu₄]₂[Pt(CF₃)₅X] (X=Cl ( 9 ), Br ( 10 )). The unusual carbonyl–platinum(IV) derivative [NBu₄][Pt(CF₃)₅(CO)] ( 6 ) is thermally stable and has a ν_CO of 2194 cm^?1. The crystal structures of 2? CH₂Cl₂, 5 , [PPh₄][Pt(CF₃)₅(CO)] ( 6′ ), and 7 have been established by X‐ray diffraction methods. Compound 2 has shown itself to be a convenient entry to the chemistry of highly trifluoromethylated platinum compounds. To the best of our knowledge, compounds 2 and 4 – 10 are the organoelement compounds with the highest CF₃ content to have been isolated and adequately characterized to date.     

Hierarchical Ni−Al hydrotalcite supported Pt catalyst for efficient catalytic oxidation of formaldehyde at room temperature

Catalytic oxidation at room temperature is recognized as the most promising method for formaldehyde (HCHO) removal. Pt-based catalysts are the optimal catalyst for HCHO decomposition at room temperature. Herein, flower-like hierarchical Pt/NiAl-LDHs catalysts with different [Ni²⁺]/[Al³⁺] molar ratios were synthesized via hydrothermal method followed by NaBH₄ reduction of Pt precursor at room temperature. The flower-like hierarchical Pt/NiAl-LDHs were composed of interlaced nanoplates and metallic Pt nanoparticles (NPs) approximately 3–4 nm in diameter were loaded on the surface of the Pt/NiAl-LDHs with high dispersion. The as-prepared Pt/NiAl21 nanocomposite was highly efficient in catalyzing oxidation of HCHO into CO₂ at room temperature. The high activity of the hierarchical Pt/NiAl21 nanocomposite was maintained after seven recycle tests, suggesting the high stability of the catalyst. Based on in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies, a reaction mechanism was put forward about HCHO decomposition at room temperature. This work provides new insights into designing and fabricating high-performance catalysts for efficient indoor air purification.     

Kinetic characterization of the interactions of trans-dichloro-platinum(IV) anticancer prodrugs and a model compound with thiosulfate

Sodium thiosulfate has been utilized as a rescuing agent for relief of the toxic effects of cisplatin and carboplatin. In this work, we characterized the kinetics of reactions of the trans-dichloro-platinum(IV) complexes cis-[Pt(NH₃)₂Cl₄], ormaplatin [Pt(dach)Cl₄] and trans-[PtCl₂(CN)₄]^2? (anticancer prodrugs and a model compound) with thiosulfate at biologically important pH. An overall second-order rate law was established for the reduction of trans-[PtCl₂(CN)₄]^2? by thiosulfate, and varying the pH from 4.45 to 7.90 had virtually no influence on the reaction rate. In the reactions of thiosulfate with cis-[Pt(NH₃)₂Cl₄] and with [Pt(dach)Cl₄], the kinetic traces displayed a fast reduction step followed by a slow substitution involving the intermediate Pt(II) complexes. The reduction step also followed second-order kinetics. Reductions of cis-[Pt(NH₃)₂Cl₄] and [Pt(dach)Cl₄] by thiosulfate proceeded with similar rates, presumably due to their similar configurations, whereas the reduction of trans-[PtCl₂(CN)₄]^2? was about 1,000 times faster. A common reduction mechanism is suggested, and the transition state for the rate-determining step has been delineated. The activation parameters are consistent with transfer of Cl⁺ from the platinum(IV) center to the attacking thiosulfate in the rate-determining step.     

Novel platinum(II) and (IV) complexes of naphthaldimine schiff bases

Naphthaldimines containing N₂O₂ donor centers react with platinum(II) and (IV) chlorides to give two types of complexes depending on the valence of the platinum ion. For [Pt(II)], the ligand is neutral, [(H₂L¹)PtCl₂]·3H₂O (1) and [(H₂L³)₂Pt₂Cl₄]·5H₂O (3), or monobasic [(HL²)₂Pt₂Cl₂]·2H₂O (2) and [(HL⁴)₂Pt]·2H₂O (4). These complexes are all diamagnetic having square-planar geometry. For [Pt(IV)], the ligand is dibasic, [(L¹)Pt₂Cl₄(OH)₂]·2H₂O (5), [(L²)Pt₃Cl₁₀]·3H₂O (6), [(L³)Pt₂Cl₄(OH)₂]·C₂H₅OH (7) and [(L⁴)Pt₂Cl₆]·H₂O (8). The Pt(IV) complexes are diamagnetic and exhibit octahedral configuration around the platinum ion. The complexes were characterized by elemental analysis, UV-Vis and IR spectra, electrical conductivity and thermal analyses (DTA and TGA). The molar conductances in DMF solutions indicate that the complexes are non-ionic. The complexes were tested for their catalytic activities towards cathodic reduction of oxygen.     

Anionic synthesis of in-chain 3° amine-functionalized polybutadienes

Anionic copolymerizations of butadiene (M₁) with excess 1-(4-dimethylaminophenyl)-1-phenylethylene (M₂) were conducted in benzene at room temperature for 24–48h using sec-butyllithium as initiator. Anisole, triethylamine and t-butyl methyl ether were added in ratios of [B]/[RLi] = 60, 20, 30, respectively, to promote copolymerization. Narrow molecular weight distribution copolymers with M̄n = 14 × 10³ to 32 × 10³ g/mol (M̄_w/M̄n =1.02–1.03) and 8,12 and 30 amine groups per chain for anisole, triethylamine and t-butyl methyl ether, respectively, were obtained. The butadiene monomer reactivity ratios (r1) were 42, 33 and 14 for anisole, triethylamine and t-butyl methyl ether, respectively.     

Stereocontrol in Dinuclear Triple Lithium‐Bridged Titanium(IV) Complexes: Solving Some Stereochemical Mysteries

Compounds 1 a – f ‐H₂ form “monomeric” triscatecholate titanium(IV) complexes [Ti( 1 a – f )₃]^2?, which in the presence of Li cations are in equilibrium with the triple lithium‐bridged “dimers” [Li₃(Ti( 1 a – f )₃)₂]^?. The equilibrium strongly depends on the donor ability of the solvent. Usually, in solvents with high donor ability, the stereochemically labile monomer is preferred, whereas in nondonor solvents, the dimer is the major species. In the latter, the stereochemistry at the complex units is “locked”. The configuration at the titanium(IV) triscatecholates is influenced by addition of chiral ammonium countercations. In this case, the induced stereochemical information at the monomer is transferred to the dimer. Alternatively, the configuration at the metal complexes can be controlled by enantiomerically pure ester side chains. Due to the different orientation of the ester groups in the monomer or dimer, opposite configurations of the triscatecholates were observed by circular dichroism (CD) spectroscopy for [Ti( 1 c – e )₃]^2? or [Li₃(Ti( 1 c – e )₃)₂]^?. A surprising exception was found for the dimer [Li₃(Ti( 1 f )₃)₂]^?. Herein, the dimer is the dominating species in weak donor (methanol), as well as strong donor (DMSO), solvents. This is due to the bulkiness of the ester substituent destabilizing the monomer. Due to the size of the substituent in [Li₃(Ti( 1 f )₃)₂]^? the esters have to adopt an unusual conformation in the dimer resulting in a stereocontrol of the small methyl group. Following this, opposite stereocontrol mechanisms were observed for the central metal‐complex units of [Li₃(Ti( 1 c – e )₃)₂]^? or [Li₃(Ti( 1 f )₃)₂]^?.     

Synthesis,characterization and optical properties of a new cationic cyclometalated platinum(ii) complex

The cyclometalated platinum (II) complex, [Pt(ppy)(ppyH)₂] OTF, 2 , in which ppy and ppyH denote the cyclometalated and non‐cyclometalated 2‐phenylpyridine ligand respectively, was prepared from the reaction of the platinum(IV) complex [PtMe₃(OTF)], 1 , with 3 equiv 2‐phenylpyridine at room temperature. The cyclometalated complex 2 was characterized using ¹H NMR spectroscopy. The solid state structure of 2 was further identified by single crystal X‐ray structure determination. 2 displays a green emission in solution and in solid state at room temperature and TD‐DFT calculations is used to elucidate the origin of the electronic transitions in the UV–vis spectrum of 2 .     

Synthetic and spectroscopic studies of some mono-hydrido-bridged complexes of platinum(II)

The mono-hydrido-bridged complexes (PEt₃)₂(Ar)Pt(μ₂-H)Pt(Ar)(PEt₃)₂]-[BPh₄] (Ar = Ph, 4-MeC₆H₄ and 2,4-Me₂C₆H₃) have been obtained by treating trans-[Pt(Ar)(MeOH)(PEt₃)₂][BF₄] with sodium formate and Na[BPH₄]. The cations [PEt₃)₂(Ar)Pt(μ₂-H)Pt(Ar^b')(PEt₃)₂]^b+ (Ar = Ph and Ar^b' - 2,4-Me₂C₆H₃ and 2,4,6-Me₃C₆H₂ have bee identified in solution. Their ^b1H- and ^b31P-NMR data are reported. The X-ray crystal structure of [(PEt₃)₂(Ph)Pt(μ₂-H)Pt(Ph)(PEt₃)₂][BPh₄] is reported.     

Synthesis and catalytic application of monometallic molybdenum(IV) nitrile complexes

The novel molybdenum(IV) compound [MoO(NCMe)₅][B(C₆F₅)₄]₂ (1a) has been prepared by air oxidation of [Mo(CO)₃(NCMe)₃] in the presence of [H(OEt₂)₂][B(C₆F₅)₄] at room temperature. The [MoO(NCMe)₅]²⁺ cation shows a distorted octahedral configuration with two different acetonitrile-metal bond lengths due to a trans effect of the oxo-ligand. The trans-acetonitrile ligand is easily abstracted under oil pump vacuum to form [MoO(NCMe)₄][B(C₆F₅)₄]₂ (1b). The complex [MoO(NCPh)₄][B(C₆F₅)₄]₂ (2) is formed by substitution of acetonitrile ligands of 1a with benzonitrile molecules. The Mo(IV) complexes can be applied in the homopolymerization of isobutene at 30 °C leading to high yields and moderate molecular weights.     

A 13C and 31P N.M.R. Investigation of restricted rotation in [Pt(η3-allyl){P(cyclohexyl)3}2]+ [PF6]- and related compounds

The dynamic behaviour of [Pt(/gh³-allyl){P(cyclohexyl)₃}₂]⁺[PF₆]^- has been reinvestigated, and the earlier interpretation of restricted rotation about the Pt—P endorsed. The activation parameters were obtained. [Pt(/gh³-allyl)(PPrⁱ₃)₂]⁺[PF₆]^- behaves similarly, while it has not prove possible to stop the rotation in [Pt(/gh³-allyl){P(CH₂Ph)₃}₂]⁺[PF₆]^-.     

A Facile Route for the Synthesis of Polycationic Tellurium Cluster Compounds: Synthesis in Ionic Liquid Media and Characterization by Single‐Crystal X‐ray Crystallography and Magnetic Susceptibility

An innovative soft chemical approach was applied, using ionic liquids as an alternative reaction medium for the synthesis of tellurium polycationic cluster compounds at room temperature. [Mo₂Te₁₂]I₆, Te₆[WOCl₄]₂, and Te₄[AlCl₄]₂ were isolated from the ionic liquid [BMIM]Cl/AlCl₃ ([BMIM]⁺: 1‐n‐butyl‐3‐methylimidazolium) and characterized. Black, cube‐shaped crystals of [Mo₂Te₁₂]I₆, which is not accessible by conventional chemical transport reaction, were obtained by reaction of the elements at room temperature in [BMIM]Cl/AlCl₃. The monoclinic structure (P2₁/n, a = 1138.92(2) pm, b = 1628.13(2) pm, c = 1611.05(2) pm, β = 105.88(1) °) is homeotypic to the triclinic bromide [Mo₂Te₁₂]Br₆. In the binulear complex [Mo₂Te₁₂]⁶⁺, the molybdenum(III) atoms are η⁴‐coordinated by terminal Te₄²⁺ rings and two bridging η²‐Te₂^2– dumbbells. Despite the short Mo···Mo distance of 297.16(5) pm, coupling of the magnetic moments is not observed. The paramagnetic moment of 3.53 μ_B per molybdenum(III) atom corresponds to an electron count of seventeen. Black crystals of monoclinic Te₆[WOCl₄]₂ are obtained by the oxidation of tellurium with WOCl₄ in [BMIM]Cl/AlCl₃. Tellurium and tellurium(IV) synproportionate in the ionic liquid at room temperature yielding violet crystals of orthorhombic Te₄[AlCl₄]₂.     

Insertion of SnCl2 into Pt–Cl bonds: synthesis and characterization of four- and five-coordinate trichlorostannylplatinum(II) complexes

Reaction of platinum(IV) chloride with SnCl₂?·?2H₂O in the presence of [NHR₃]₃Cl (R?=?Me, Et) in 3M hydrochloric acid affords the anionic five-coordinate platinum(II) complexes [NHR₃]₃[Pt(SnCl₃)₅], R?=?Me (1), Et (2), respectively. Moreover, platinum(IV) chloride reacts with SnCl₂?·?2H₂O in the presence of bis(triphenylphosphoranylidene)ammonium chloride in acetone/dichloromethane to form [N(PPh₃)₂]₃[Pt(SnCl₃)₅] (3). In contrast, reaction of an acetone solution of platinum(IV) chloride with SnCl₂?·?2H₂O in the presence of bis(triphenylphosphoranylidene) ammonium chloride resulted in the formation of cis-[N(PPh₃)₂]₂[PtCl₂(SnCl₃)₂] (4). The same products are obtained by using a platinum(II) salt as starting material. Similarly, cis and trans- dichlorobis(diethyl sulfide)platinum(II) reacts with SnCl₂?·?2H₂O in 5M hydrochloric acid to give [PtCl(SEt₂)₃]₃[Pt(SnCl₃)₅] (5) by facile insertion of SnCl₂ into the Pt–Cl bond. However, treatment of an acetone solution of cis- and trans-[PtCl₂(SEt₂)₂] with SnCl₂?·?2H₂O in the presence of a small amount of HCl resulted in the formation of 5, which dissociates in solution to give [PtCl₂(SEt₂)₂]. The complexes have been fully characterized by elemental analysis and multinuclear NMR (¹H,?¹³C,?¹⁹⁵Pt,?¹¹⁹Sn) spectroscopy. A structure determination of crystals grown from a solution of 2 by X-ray diffraction methods shows that platinum adopts a regular trigonal bipyramidal geometry.     

Synthesis, EPR spectrum and X-ray structure of tetra-n-butylammonium bis(benzene-1,2-dithiolato(2−)-κS,S′)platinate(III)

The new salt, tetra-n-butylammonium bis(benzene-1,2-dithiolato(2−)-κ²S,S′)platinate(III), [NBu₄][Pt(C₆H₄S₂)₂] (1), has been synthesized in ethanol/water, and fully characterized by single crystal X-ray structure determination. The central platinum in the complex ion [Pt(bdt)₂]⁻ is tetracoordinated by the S atoms of the bdt²⁻ ligands (bdt²⁻ is benzene-1,2-dithiolate) in a square-planar geometry. The well-resolved frozen solution EPR spectrum exhibits rhombic symmetry. The room temperature effective magnetic moment (μ_eff = 1.80 Bohr magneton) is in line with this spectrum and strongly supports the Pt(III) oxidation state in 1. This observation is in excellent agreement with previous results reported on closely related Ni(III), Pd(III) and Pt(III) species.