Solvent-Driven P–S vs P–C Bond Formation from a Diplatinum(III) Complex and Sulfur-Based Anions

The outcome of the reaction of the Pt­(III),Pt­(III) complex [(C₆F₅)₂Pt^III(μ-PPh₂)₂Pt^III(C₆F₅)₂]­(<i>Pt–Pt</i>) (<b>1</b>) with the S-based anions thiophenoxide (PhS^–), ethyl xanthogenate (EtOCS₂^–), 2-mercaptopyrimidinate (pymS^–), and 2-mercaptopyridinate (pyS^–) was found to be dependent on the reaction solvent. The reactions carried out in acetone led to the formation of [NⁿBu₄]­[(R_F)₂Pt^II(μ-PhS-PPh₂)­(μ-PPh₂)­Pt^II(R_F)₂] (<b>2</b>), [NⁿBu₄]­[(R_F)₂Pt^II(μ-EtOCS₂-PPh₂)­(μ-PPh₂)­Pt^II(R_F)₂] (<b>3</b>), [NⁿBu₄]­[(R_F)₂Pt^II(μ-pymS-PPh₂)­(μ-PPh₂)­Pt^II(R_F)₂] (<b>4</b>), and [NⁿBu₄]­[(R_F)₂Pt^II(μ-pyS–PPh₂)­(μ-PPh₂)­Pt^II(R_F)₂] (<b>5</b>), respectively (R_F = C₆F₅). Complexes <b>2</b>–<b>5</b> display new Ph₂P­(SL) ligands exhibiting a κ²-<i>P</i>,<i>S</i> bridging coordination mode, which is derived from a reductive elimination of a PPh₂ group and the S-based anion. Carrying out the reaction in dichloromethane afforded, in the cases of EtOCS₂^– and pymS^–, the monobridged complexes [NⁿBu₄]­[(PPh₂R_F)­(R_F)₂Pt^II(μ-PPh₂)­Pt^II(EtOCS₂)­(R_F)] (<b>6</b>) and [NⁿBu₄]­[(PPh₂R_F)­(R_F)₂Pt^II(μ-PPh₂)­Pt^II(pymS)­(R_F)] (<b>7</b>), respectively, which are derived from reductive elimination of a PPh₂ group with a pentafluorophenyl ring. The reaction of <b>1</b> with EtOCS₂K in acetonitrile yielded a mixture of <b>3</b> and <b>6</b> as a consequence of the concurrence of two processes: (a) the formation of <b>3</b> by a reaction that parallels the formation of <b>3</b> by <b>1</b> plus EtOCS₂K in acetone and (b) the transformation of <b>1</b> into the neutral complex [(PPh₂R_F)­(CH₃CN)­(R_F)­Pt^II(μ-PPh₂)­Pt^II(R_F)₂(CH₃CN)] (<b>8</b>), which, in turn, reacts with EtOCS₂K to give <b>6</b>. The <b>1</b> to <b>8</b> transformation was found to be fully reversible. In fact, dissolving <b>8</b> in acetone or dichloromethane afforded pure <b>1</b> after solvent evaporation or crystallization with <i>n</i>-hexane. The XRD structures of <b>2</b>–<b>4</b> and <b>6</b>–<b>8</b> were determined, and the behavior in solution of the new complexes is discussed

Cardiomyocyte Apoptosis and Cardiac Angiotensin-Converting Enzyme in Spontaneously Hypertensive Rats

Abstract Increased apoptosis has been reported in the heart of rats with spontaneous hypertension and cardiac hypertrophy. This study was designed to investigate the relationship between apoptosis and hypertrophy in cardiomyocytes from the left ventricle of spontaneously hypertensive rats (SHR). In addition, we evaluated whether the development of cardiomyocyte apoptosis is related to blood pressure or to the activity of the local angiotensin-converting enzyme (ACE) in SHR. The study was performed in 16-week-old SHR, 30-week-old untreated SHR, and 30-week-old SHR treated with quinapril (10 mg · kg −1 · d −1 ) during 14 weeks before they were killed. Cardiomyocyte apoptosis was assessed by direct immunoperoxidase detection of digoxigenin-labeled 3′-hydroxyl ends of DNA. Nuclear polyploidization measured by DNA flow cytometry was used to assess cardiomyocyte hypertrophy. Compared with 16-week-old normotensive Wistar-Kyoto rats, 16-week-old SHR exhibited increased blood pressure ( P <.001), increased rate of tetraploidy ( P <.05), and similar levels of ACE activity and apoptosis. Compared with 30-week-old Wistar-Kyoto rats, 30-week-old SHR showed increased blood pressure ( P <.001), increased ACE activity ( P <.05), increased rate of tetraploidy ( P <.01), and increased apoptosis ( P <.01). Untreated 30-week-old SHR exhibited similar values of blood pressure and tetraploidy and higher ACE activity ( P <.05) and apoptosis ( P <.001) than 16-week-old SHR. A direct correlation ( P <.01) was found between ACE activity and the apoptotic index in untreated 30-week-old SHR. The long-term administration of quinapril was associated with the normalization of ACE activity and apoptosis in treated SHR. These results suggest that the timing and mechanisms responsible for apoptosis and hypertrophy of cardiomyocytes are different in SHR. Whereas hypertrophy seems to be an earlier alteration that develops in parallel with hypertension, apoptosis develops later in association with overactivity of the local ACE. Our data suggest that cell death dysregulation may be a novel target for antihypertensive agents that interfere with the renin-angiotensin system in hypertension

Seagrass Posidonia is impaired by human-generated noise

Solé et al. report morphological and ultrastructural changes in seagrass, after exposure to human generated noise. These data suggest that noise pollution can potentially affect the health status of seagrass and thereby contribute to the depletion of seagrass populations

Resolving Light Handedness with an on-Chip Silicon Microdisk

The efficient manipulation of circularly polarized light with the proper handedness is key in many photonic applications. Chiral structures are capable of distinguishing photon handedness, but while photons with the right polarization are captured, those of opposite handedness are rejected. In this work, we demonstrate a planar photonic nanostructure with no chirality consisting of a silicon microdisk coupled to two waveguides. The device distinguishes the handedness of an incoming circularly polarized light beam by driving photons with opposite spins toward different waveguides. Experimental results are in close agreement with numerical results, which predict extinction ratios over 18 dB in a 20 nm bandwidth. Owing to reciprocity, the device can also emit right or left circular polarization depending on the chosen feeding waveguide. Although implemented here on a CMOS-compatible platform working at telecom wavelengths, the fundamental approach is general and can be extended to any frequency regime and technological platform

Synthesis and Reactivity of the Unsaturated Trinuclear Phosphanido Complex [(C₆F₅)₂Pt(μ-PPh₂)₂Pt(μ-PPh₂)₂Pt(PPh₃)]

The reaction of [NBu₄]­[(C₆F₅)₂Pt­(μ-PPh₂)₂Pt­(μ-PPh₂)₂Pt­(<i>O</i>,<i>O</i>-acac)] (48 VEC) with [HPPh₃]­[ClO₄] gives the 46 VEC unsaturated [(C₆F₅)₂Pt¹(μ-PPh₂)₂Pt²(μ-PPh₂)₂Pt³(PPh₃)]­(Pt²–Pt³) (<b>1</b>), a trinuclear compound endowed with a Pt–Pt bond. This compound displays amphiphilic behavior and reacts easily with nucleophiles L, yielding the saturated complexes [(C₆F₅)₂Pt^II(μ-PPh₂)₂Pt^II(μ-PPh₂)₂Pt^II(PPh₃)­L] [L = PPh₃ (<b>2</b>), py (<b>3</b>)]. The reaction with the electrophile [Ag­(OClO₃)­PPh₃] affords the adduct <b>1</b>·AgPPh₃, which evolves, even at low temperature, to a mixture in which [(C₆F₅)₂Pt^III(μ-PPh₂)₂Pt^III(μ-PPh₂)₂Pt^II(PPh₃)₂]²⁺(Pt^III–Pt^III) and <b>2</b> (plus silver metal) are present. The nucleophilic nature of <b>1</b> is also demonstrated through its reaction with <i>cis</i>-[Pt­(C₆F₅)₂(THF)₂], which results in the formation of [Pt₄(μ-PPh₂)₄(C₆F₅)₄(PPh₃)] (<b>4</b>). The structure and NMR features indicate that <b>1</b> can be better considered as a Pt^II–Pt^III–Pt^I complex instead of a Pt^II–Pt^II–Pt^II derivative. Theoretical calculations (density functional theory) on similar model compounds are in agreement with the assigned oxidation states of the metal centers. The strong intermetallic interactions resulting in a Pt²–Pt³ metal–metal bond and the respective bonding mechanism were verified by employing a multitude of computational techniques (natural bond order analysis, the Laplacian of the electron density, and localized orbital locator profiles)

Oxidatively Induced P–O Bond Formation through Reductive Coupling between Phosphido and Acetylacetonate, 8‑Hydroxyquinolinate, and Picolinate Groups

The dinuclear anionic complexes [NBu₄]­[(R_F)₂M^II(μ-PPh₂)₂M′^II(N^∧O)] (R_F = C₆F₅. N^∧O = 8-hydroxyquinolinate, hq; M = M′ = Pt <b>1</b>; Pd <b>2</b>; M = Pt, M′ = Pd, <b>3</b>. N^∧O = <i>o</i>-picolinate, pic; M = Pt, M′ = Pt, <b>4</b>; Pd, <b>5</b>) are synthesized from the tetranuclear [NBu₄]₂[{(R_F)₂Pt­(μ-PPh₂)₂M­(μ-Cl)}₂] by the elimination of the bridging Cl as AgCl in acetone, and coordination of the corresponding <i>N</i>,<i>O</i>-donor ligand (<b>1</b>, <b>4</b>, and <b>5</b>) or connecting the fragments “<i>cis</i>-[(R_F)₂M­(μ-PPh₂)₂]^2–” and “M′(N^∧O)” (<b>2</b> and <b>3</b>). The electrochemical oxidation of the anionic complexes <b>1</b>–<b>5</b> occurring under HRMS­(+) conditions gave the cations [(R_F)₂M­(μ-PPh₂)₂M′(N^∧O)]⁺, presumably endowed with a M­(III),M′(III) core. The oxidative addition of I₂ to the 8-hydroxyquinolinate complexes <b>1</b>–<b>3</b> triggers a reductive coupling between a PPh₂ bridging ligand and the <i>N</i>,<i>O</i>-donor chelate ligand with formation of a P–O bond and ends up in complexes of platinum­(II) or palladium­(II) of formula [(R_F)₂M^II(μ-I)­(μ-PPh₂)­M′^II(<i>P</i>,<i>N</i>-PPh₂hq)], M = M′ = Pt <b>7</b>, Pd <b>8</b>; M = Pt, M′ = Pd, <b>9</b>. Complexes <b>7</b>–<b>9</b> show a new Ph₂P-OC₉H₆N (Ph₂P-hq) ligand bonded to the metal center in a <i>P</i>,<i>N</i>-chelate mode. Analogously, the addition of I₂ to solutions of the <i>o</i>-picolinate complexes <b>4</b> and <b>5</b> causes the reductive coupling between a PPh₂ bridging ligand and the starting <i>N</i>,<i>O</i>-donor chelate ligand with formation of a P–O bond, forming Ph₂P-OC₆H₄NO (Ph₂P-pic). In these cases, the isolated derivatives [NBu₄]­[(Ph₂P-pic)­(R_F)­Pt^II(μ-I)­(μ-PPh₂)­M^II(R_F)­I] (M = Pt <b>10</b>, Pd <b>11</b>) are anionic, as a consequence of the coordination of the resulting new phosphane ligand (Ph₂P-pic) as monodentate <i>P</i>-donor, and a terminal iodo group to the M atom. The oxidative addition of I₂ to [NBu₄]­[(R_F)₂Pt^II(μ-PPh₂)₂Pt^II(acac)] (<b>6</b>) (acac = acetylacetonate) also results in a reductive coupling between the diphenylphosphanido and the acetylacetonate ligand with formation of a P–O bond and synthesis of the complex [NBu₄]­[(R_F)₂Pt^II(μ-I)­(μ-PPh₂)­Pt^II(Ph₂P-acac)­I] (<b>12</b>). The transformations of the starting complexes into the products containing the P–O ligands passes through mixed valence M­(II),M′(IV) intermediates which were detected, for M = M′ = Pt, by spectroscopic and spectrometric measurements

Addition of Nucleophiles to Phosphanido Derivatives of Pt(III): Formation of P–C, P–N, and P–O Bonds

The reactivity of the dinuclear platinum­(III) derivative [(R_F)₂Pt^III(μ-PPh₂)₂­Pt^III(R_F)₂]<i>(Pt–Pt)</i> (R_F = C₆F₅) (<b>1</b>) toward OH^–, N₃^–, and NCO^– was studied. The coordination of these nucleophiles to a metal center evolves with reductive coupling or reductive elimination between a bridging diphenylphosphanido group and OH^–, N₃^–, and NCO^– or C₆F₅ groups and formation of P–O, P–N, or P–C bonds. The addition of OH^– to <b>1</b> evolves with a reductive coupling with the incoming ligand, formation of a P–O bond, and the synthesis of [NBu₄]₂[(R_F)₂Pt^II(μ-OPPh₂)­(μ-PPh₂)­Pt^II(R_F)₂] (<b>3</b>). The addition of N₃^– takes place through two ways: (a) formation of the P–N bond and reductive elimination of PPh₂N₃ yielding [NBu₄]₂[(R_F)₂Pt^II(μ-N₃)­(μ-PPh₂)­Pt^II(R_F)₂] (<b>4a</b>) and (b) formation of the P–C bond and reductive coupling with one of the C₆F₅ groups yielding [NBu₄]­[(R_F)₂Pt^II(μ-N₃)­(μ-PPh₂)­Pt^II(R_F)­(PPh₂R_F)] (<b>4b</b>). Analogous behavior was shown in the addition of NCO^– to <b>1</b> which afforded [NBu₄]₂[(R_F)₂Pt^II(μ-NCO)­(μ-PPh₂)­Pt^II(R_F)₂] (<b>5a</b>) and [NBu₄]­[(R_F)₂Pt^II(μ-NCO)­(μ-PPh₂)­Pt^II(R_F)­(PPh₂R_F)] (<b>5b</b>). In the reaction of the trinuclear complex [(R_F)₂Pt^III(μ-PPh₂)₂Pt^III(μ-PPh₂)₂­Pt^II(R_F)₂]<i>(Pt</i>^<i>III</i><i>–Pt</i>^<i>III</i><i>)</i> (<b>2</b>) with OH^– or N₃^–, the coordination of the nucleophile takes place selectively at the central platinum­(III) center, and the PPh₂/OH^– or PPh₂/N₃^– reductive coupling yields the trinuclear [NBu₄]₂[(R_F)₂Pt^II(μ-Ph₂PO)­(μ-PPh₂)­Pt^II(μ-PPh₂)₂Pt^II(R_F)₂] (<b>6</b>) and [NBu₄]­[(R_F)₂Pt¹(μ₃-Ph₂PNPPh₂)­(μ-PPh₂)­Pt²(μ-PPh₂)­Pt³(R_F)₂]<i>(Pt</i>^<i>2</i><i>–Pt</i>^<i>3</i><i>)</i> (<b>7</b>). Complex <b>7</b> is fluxional in solution, and an equilibrium consisting of Pt–Pt bond migration was ascertained by ³¹P EXSY experiments

Multinuclear Solid-State NMR and DFT Studies on Phosphanido-Bridged Diplatinum Complexes

Multinuclear (³¹P, ¹⁹⁵Pt, ¹⁹F) solid-state NMR experiments on (<i>n</i>Bu₄N)₂[(C₆F₅)₂Pt­(μ-PPh₂)₂Pt­(C₆F₅)₂] (<b>1</b>), [(C₆F₅)₂Pt­(μ-PPh₂)₂Pt­(C₆F₅)₂]­(<i>Pt–Pt</i>) (<b>2</b>), and <i>cis</i>-Pt­(C₆F₅)₂(PHPh₂)₂ (<b>3</b>) were carried out under cross-polarization/magic-angle-spinning conditions or with the cross-polarization/Carr–Purcell Meiboom–Gill pulse sequence. Analysis of the principal components of the ³¹P and ¹⁹⁵Pt chemical shift (CS) tensors of <b>1</b> and <b>2</b> reveals that the variations observed comparing the isotropic chemical shifts of <b>1</b> and <b>2</b>, commonly referred to as “ring effect”, are mainly due to changes in the principal components oriented along the direction perpendicular to the Pt₂P₂ plane. DFT calculations of ³¹P and ¹⁹⁵Pt CS tensors confirmed the tensor orientation proposed from experimental data and symmetry arguments and revealed that the different values of the isotropic shieldings stem from differences in the paramagnetic and spin–orbit contributions