Revisiting CO₂ Reduction with NaBH₄ under Aprotic Conditions: Synthesis and Characterization of Sodium Triformatoborohydride

The reduction of CO₂ to formate using sodium borohydride was originally investigated in the 1950s. Despite this clue from the chemical literature, many recent publications describe catalytic CO₂ hydroboration methods leading to formate or methoxide with more expensive and less reactive boranes such as pinacolborane. Herein we describe the uptake of 3 equiv of CO₂ by NaBH₄, along with full spectroscopic and crystallographic characterization of the resulting triformatoborohydride, Na­[HB­(OCHO)₃]. Conducting the synthesis in acetonitrile under 300 psi of CO₂ constitutes a new preparative procedure for generating Na­[HB­(OCHO)₃]. This reaction does not require the presence of a strongly coordinating alkali metal cation, as evidenced by the analogous reactivity of [NEt₄]­[BH₄]. Even at 1 atm pressure and without using rigorously dry solvent, treatment of NaBH₄ with CO₂ and subsequent quenching gave formic acid (1.5 equiv based on B)

Facile Synthesis of Dibenzo-7λ³‑phosphanorbornadiene Derivatives Using Magnesium Anthracene

Unprotected dibenzo-7λ³-phosphanorbornadiene derivatives RP<b>A</b> (<b>A</b> = C₁₄H₁₀ or anthracene; R = ^<i>t</i>Bu, dbabh = N<b>A</b>, HMDS = (Me₃Si)₂N, ^<i>i</i>Pr₂N) are synthesized by treatment of the corresponding phosphorus dichloride RPCl₂ with Mg<b>A</b>·3THF, in cold THF (∼20% to 30% isolated yields). Anthracene and the corresponding cyclic phosphane (RP)_<i>n</i> form as coproducts. Characteristic NMR features of the RP<b>A</b> derivatives include a doublet near 4 ppm in their ¹H NMR spectra and a triplet peak in the 175–212 ppm region of the ³¹P NMR spectrum (²<i>J</i>_PH ∼14 Hz). The X-ray structures of the <b>A</b>N–P<b>A</b> and (HMDS)­P<b>A</b> derivatives are discussed. Thermolysis of RP<b>A</b> benzene-<i>d</i>₆ solutions leads to anthracene extrusion. This process has a unimolecular kinetic profile for the ^<i>i</i>Pr₂NP<b>A</b> derivative. The 7-phosphanorbornene <i>anti</i>-^<i>i</i>Pr₂NP­(C₆H₈) could be synthesized (70% isolated yield) by thermolysis of ^<i>i</i>Pr₂NP<b>A</b> in 1,3-cyclohexadiene

Facile Synthesis of Dibenzo-7λ³‑phosphanorbornadiene Derivatives Using Magnesium Anthracene

Unprotected dibenzo-7λ³-phosphanorbornadiene derivatives RP<b>A</b> (<b>A</b> = C₁₄H₁₀ or anthracene; R = ^<i>t</i>Bu, dbabh = N<b>A</b>, HMDS = (Me₃Si)₂N, ^<i>i</i>Pr₂N) are synthesized by treatment of the corresponding phosphorus dichloride RPCl₂ with Mg<b>A</b>·3THF, in cold THF (∼20% to 30% isolated yields). Anthracene and the corresponding cyclic phosphane (RP)_<i>n</i> form as coproducts. Characteristic NMR features of the RP<b>A</b> derivatives include a doublet near 4 ppm in their ¹H NMR spectra and a triplet peak in the 175–212 ppm region of the ³¹P NMR spectrum (²<i>J</i>_PH ∼14 Hz). The X-ray structures of the <b>A</b>N–P<b>A</b> and (HMDS)­P<b>A</b> derivatives are discussed. Thermolysis of RP<b>A</b> benzene-<i>d</i>₆ solutions leads to anthracene extrusion. This process has a unimolecular kinetic profile for the ^<i>i</i>Pr₂NP<b>A</b> derivative. The 7-phosphanorbornene <i>anti</i>-^<i>i</i>Pr₂NP­(C₆H₈) could be synthesized (70% isolated yield) by thermolysis of ^<i>i</i>Pr₂NP<b>A</b> in 1,3-cyclohexadiene

Thrombus composition in acute coronary syndrome

Atherothrombosis and, specifically intracoronary thrombosis is a major cause of acute coronary syndromes (ACS) and consequently of morbidity and mortality throughout the world. While management of acute ST-elevation myocardial infarction (STEMI) has dramatically improved over the last years, there is still a need to find thrombosis-related biomarkers for an early identification of ischemic processes and a better stratification of patients that have suffered an ACS. In fact, the ischemia time, defined as the time from the onset of symptoms to reperfusion, has been recently suggested as the “New Gold Standard for STEMI-Care”. This thesis mainly focuses on the protein composition of the occluding coronary thrombus, occurring both in the native coronary arteries and in the commonly implanted coronary stents. The study based on the proteomic analysis of coronary thrombi, obtained after percutaneous coronary intervention (PCI), has provided consistent evidence of the dynamic composition of the coronary thrombi in relation with the time of ischemia, and has resulted in the identification of novel biomarkers of potential use to be translated to the clinical practice. Furthermore, the comparison of native and in-stent-thrombosis has allowed the identification of proteins that might serve as interesting therapeutic targets to prevent thrombosis in patients who undergo PCI with stent-implantation.La enfermedad aterotrombotica y concretamente la trombosis intracoronaria es la mayor causa de los síndromes coronarios agudos (SCA), y consecuentemente de morbilidad y mortalidad en el mundo. El manejo de los pacientes con infarto agudo de miocardio con elevación del segmento ST ha mejorado considerablemente en los últimos años, a pesar de esto sigue siendo necesario encontrar biomarcadores para la detección temprana de los procesos isquémicos y que permitan una estratificación más eficiente de los pacientes que han sufrido un evento isquémico agudo. De hecho, el tiempo de isquemia, definido como el tiempo entre el inicio del dolor y la revascularización, ha sido recientemente definido como el parámetro fundamental en el tratamiento de los pacientes con STEMI. Este trabajo de tesis está enfocado a elucidar la composición proteica de los trombos coronarios oclusivos que se forman tanto en las arterias coronarias nativas como en aquellas con stent. El estudio se basa en el análisis proteómico de trombos coronarios en relación al tiempo de isquemia, con la finalidad de encontrar nuevos biomarcadores para trasladar a la práctica clínica. Además, la comparación entre trombos nativos y trombos desarrollados sobre el stent permite la identificación de proteínas diferenciales que podrían ser futuras dianas terapéuticas para prevenir la formación del trombo en pacientes sometidos a angioplastia coronaria transluminal percutánea (ACTP) con implantación de un stent coronario

Facile Synthesis of Dibenzo-7λ³‑phosphanorbornadiene Derivatives Using Magnesium Anthracene

Unprotected dibenzo-7λ³-phosphanorbornadiene derivatives RP<b>A</b> (<b>A</b> = C₁₄H₁₀ or anthracene; R = ^<i>t</i>Bu, dbabh = N<b>A</b>, HMDS = (Me₃Si)₂N, ^<i>i</i>Pr₂N) are synthesized by treatment of the corresponding phosphorus dichloride RPCl₂ with Mg<b>A</b>·3THF, in cold THF (∼20% to 30% isolated yields). Anthracene and the corresponding cyclic phosphane (RP)_<i>n</i> form as coproducts. Characteristic NMR features of the RP<b>A</b> derivatives include a doublet near 4 ppm in their ¹H NMR spectra and a triplet peak in the 175–212 ppm region of the ³¹P NMR spectrum (²<i>J</i>_PH ∼14 Hz). The X-ray structures of the <b>A</b>N–P<b>A</b> and (HMDS)­P<b>A</b> derivatives are discussed. Thermolysis of RP<b>A</b> benzene-<i>d</i>₆ solutions leads to anthracene extrusion. This process has a unimolecular kinetic profile for the ^<i>i</i>Pr₂NP<b>A</b> derivative. The 7-phosphanorbornene <i>anti</i>-^<i>i</i>Pr₂NP­(C₆H₈) could be synthesized (70% isolated yield) by thermolysis of ^<i>i</i>Pr₂NP<b>A</b> in 1,3-cyclohexadiene

Terminal Titanyl Complexes of Tri- and Tetrametaphosphate: Synthesis, Structures, and Reactivity with Hydrogen Peroxide

The synthesis and characterization of tri- and tetrametaphosphate titanium­(IV) oxo and peroxo complexes is described. Addition of 0.5 equiv of [OTi­(acac)₂]₂ to dihydrogen tetrametaphosphate ([P₄O₁₂H₂]^2–) and monohydrogen trimetaphosphate ([P₃O₉H]^2–) provided a bis­(μ₂,κ²,κ²) tetrametaphosphate titanyl dimer, [OTiP₄O₁₂]₂^4– (<b>1</b>; 70% yield), and a trimetaphosphate titanyl acetylacetonate complex, [OTiP₃O₉(acac)]^2– (<b>2</b>; 59% yield). Both <b>1</b> and <b>2</b> have been structurally characterized, crystallizing in the triclinic <i>P</i>1̅ and monoclinic <i>P</i>2₁ space groups, respectively. These complexes contain TiO units with distances of 1.624(7) and 1.644(2) Å, respectively, and represent rare examples of structurally characterized terminal titanyls within an all-oxygen coordination environment. Complexes <b>1</b> and <b>2</b> react with hydrogen peroxide to produce the corresponding peroxotitanium­(IV) metaphosphate complexes [O₂TiP₄O₁₂]₂^4–(<b>3</b>; 61% yield) and [O₂TiP₃O₉(acac)]^2– (<b>4</b>; 65% yield), respectively. Both <b>3</b> and <b>4</b> have been characterized by single-crystal X-ray diffraction studies, and their solid-state structures are presented. Complex <b>3</b> functions as an oxygen atom transfer (OAT) reagent capable of oxidizing phosphorus­(III) compounds (P­(OMe)₃, PPh₃) and SMe₂ at ambient temperature to result in the corresponding organic oxide with regeneration of dimer <b>1</b>

Synthesis, Characterization, and Thermolysis of Dibenzo-7-dimethylgermanorbornadiene

The dibenzo-7-dimethylgermanorbornadiene Me₂Ge<b>A</b> (<b>A</b> <i> = </i> C₁₄H₁₀) has been synthesized in one step by treatment of Mg<b>A</b>·3THF with Me₂GeCl₂ in tetrahydrofuran (−35 °C) and isolated in 69% yield. The thermolysis of Me₂Ge<b>A</b> in toluene leads to the effective expansion of the bicyclic framework to the dibenzo-7,8-tetramethyldigermabicyclo[2.2.2]­octadiene (Me₂Ge)₂<b>A</b>, isolated in 71% yield (based on germanium). The bicyclic compounds Me₂Ge<b>A</b> and (Me₂Ge)₂<b>A</b> have been characterized by single-crystal X-ray diffraction studies and their structures discussed

Synthesis, Characterization, and Thermolysis of Dibenzo-7-dimethylgermanorbornadiene

The dibenzo-7-dimethylgermanorbornadiene Me₂Ge<b>A</b> (<b>A</b> <i> = </i> C₁₄H₁₀) has been synthesized in one step by treatment of Mg<b>A</b>·3THF with Me₂GeCl₂ in tetrahydrofuran (−35 °C) and isolated in 69% yield. The thermolysis of Me₂Ge<b>A</b> in toluene leads to the effective expansion of the bicyclic framework to the dibenzo-7,8-tetramethyldigermabicyclo[2.2.2]­octadiene (Me₂Ge)₂<b>A</b>, isolated in 71% yield (based on germanium). The bicyclic compounds Me₂Ge<b>A</b> and (Me₂Ge)₂<b>A</b> have been characterized by single-crystal X-ray diffraction studies and their structures discussed

Cobalt Complexes Supported by <i>cis</i>-Macrocyclic Diphosphines: Synthesis, Reactivity, and Activity toward Coupling Carbon Dioxide and Ethylene

The coordination chemistry of <i>cis</i>-macrocyclic diphosphines readily accessed from white phosphorus was explored, with a focus on preparing and studying cobalt complexes. <i>cis</i>-1,6-Dicyclohexyl-3,4,8,9-tetramethyl-2,5,7,10-tetrahydro-1,6-DiPhospheCine, or Cy₂–DPC (<b>1</b>), was primarily used as a model diphosphine. Cobalt­(II) dihalide diphosphine complexes such as (Cy₂–DPC)­CoX₂, X = Cl (<b>2</b>) and I (<b>3</b>), were prepared, and their reactivity toward a variety of reducing agents was studied. We were successful in preparing and structurally characterizing an unusual iodide-bridged cobalt­(I) dimer, [(Cy₂–DPC)­CoI]₂ (<b>8</b>). These cobalt complexes were also investigated as potential catalysts for the coupling of carbon dioxide and ethylene to produce acrylate, a valuable polymer precursor. Although not yet catalytic, the first examples of cobalt complexes capable of mediating this transformation are reported. Notably, the well-known commercial complex ClCo­(PPh₃)₃ was also found to be active in mediating acrylate production. As part of our mechanistic investigation, a pseudotetrahedral cobalt methyl acrylate complex, (Cy₂–DPC)­CoI­(CH₂CHCOOMe) (<b>10</b>), was prepared and structurally characterized

Phosphinidene Reactivity of a Transient Vanadium PN Complex

Toward the preparation of a coordination complex of the hetero­diatomic molecule PN, PN-V­(N­[^<i>t</i>Bu]­Ar)₃ (<b>1</b>, Ar = 3,5-Me₂­C₆H₃), we report the use of ClP<b>A</b> (<b>A</b> = C₁₄H₁₀, anthracene) as a formal source of phosphorus­(I) in its reaction with Na­[NV­(N­[^<i>t</i>Bu]­Ar)₃] (Na­[<b>4</b>]) to yield trimeric cyclo-triphosphane [PNV­(N­[^<i>t</i>Bu]­Ar)₃]₃ (<b>3</b>) with a core composed exclusively of phosphorus and nitrogen. In the presence of NapS₂ (<i>peri</i>-1,8-naphthalene disulfide), NapS₂P-NV­(N­[^<i>t</i>Bu]­Ar)₃ (<b>6</b>) is instead generated in 80% yield, suggesting trapping of transient <b>1</b>. Upon mild heating, <b>3</b> readily fragments into dimeric [PNV­(N­[^<i>t</i>Bu]­Ar)₃]₂ (<b>2</b>), while in the presence of bis­(trimethyl­silyl)­acetylene or <i>cis</i>-4-octene, the respective phosphirene (Ar­[^<i>t</i>Bu]­N)₃­VN-PC₂­(SiMe₃)₂ (<b>7</b>) or phosphirane (Ar­[^<i>t</i>Bu]­N)₃­VN-P­(C₈H₁₆) (<b>8</b>) compounds are generated. Kinetic data were found to be consistent with unimolecular decay of <b>3</b>, and [2+1]-cycloaddition with radical clocks ruled out a triplet intermediate, consistent with intermediate <b>1</b> reacting as a singlet phosphin­idene. In addition, both <b>7</b> and <b>8</b> were shown to reversibly exchange <i>cis</i>-4-octene and bis­(trimethyl­silyl)­acetylene, serving as formal sources of <b>1</b>, a reactivity manifold traditionally reserved for transition metals