Preparation of silyl-terminated branched polyethylenes catalyzed by Brookhart's nickel diimine complex activated with hydrosilane/B(C6F5)3

Brookhart's nickel α-diimine complex [(κ2-N,N-BIAN)NiCl2] (1) (where BIAN = {Ar-NAceN-Ar}, Ace = acenaphthen-1,2-diyl, and Ar = 2,6-(iPr)2-C6H3) activated with a hydrosilane/B(C6F5)3 (SiHB) adduct forms a highly active catalytic system for ethylene polymerization. Under optimal conditions, the activity of the system depends on the nature of hydrosilane and decreases in the order R3SiH > Ph2SiH2 > PhSiH3. The decrease in system activity within the hydrosilane series is correlated with increasing formation of Ni(I) species. In addition to their activation effect, hydrosilanes act as efficient chain termination/chain transfer agents, with the Si/Ni ratio controlling the molecular weight of the resulting polyethylene (PE). The use of Et3SiH generated elastomeric, highly branched polymers with a saturated chain-end, while systems using Ph2SiH2 and PhSiH3 led to branched end-functionalized PEs terminated with the hydrosilyl functionality (i.e. br-PE-SiPh2H or br-PE-SiPhH2).

Reactions of permethyltitanocene tucked-in derivatives with carbon dioxide

Both single tucked-in permethyltitanocene 1 and double tucked-in permethyltitanocene 2 react with excess CO₂ by insertion into their Ti-CH₂ bonds. The former one precipitates instantly a yellow carboxylate-tethered oligomer [3]_n which is insoluble in aprotic solvents and in a vacuum it sublimes as a monomer without decomposition. Computations for n ≤ 4 optimised the structure of the monomer [3] and showed that open chain oligomers bound by dative O → Ti bonds were not sterically hindered. The latter bond dissociates when [3]_n is oxidized by chlorination with CDCl₃ or CD₂Cl₂ to give Ti(IV) chloride 4 or upon metathesis of [3]_n with Me₃SiCl yielding Ti(III) chloride 5. Oxidative addition of MeCN affords a C-C coupled dinuclear titanocene diimine 6. Compound [3]_n also reacts with 1 to give the tethered carbodiolate 8 or with [Cp*₂TiH] (where Cp* = η⁵-C₅Me₅) to give the half-tethered carbodiolate 10. The non-tethered carbodiolate 12 was obtained from [Cp*₂TiH] and CO₂ yielding titanocene formate by reaction of the latter with another equivalent of [Cp*₂TiH]. All these carbodiolates contain Ti(III) metal atoms forming electronic triplet states of axial or orthorhombic symmetry. In contrast to the rapidly reacting 1 compound 2 reacts with excess CO₂ slowly in m-xylene at 100 °C using only one of its two Ti-CH₂ moieties. The structure of the obtained carbodiolate 13 indicates that the primary product analogous to 3 reacts with 2 more rapidly than with CO₂.

Comparison of inpatient and outpatient cardiac rehabilitation following myocardial infarction

Funding Acknowledgements

Type of funding sources: None.

Background

Cardiac rehabilitation (CR) following myocardial infarction (MI) improves prognosis. Models of second phase CR differ across countries. The aim of the study was to compare outcomes in MI survivors participating in outpatient and inpatient CR programmes.

Methods

We included all patients hospitalized due to acute MI in Poland between October 2017 and December 2018 (n=96634). Among them 4411 patients were referred to and commenced outpatient CR, whereas 11626 patients started inpatient CR within 30 days following discharge. All the patients were the subject of prospective follow-up. The primary endpoint was defined as death from any cause.

Results

The mean follow-up was 332.8±128.1 days. Younger age, male sex, and a cancer in the history were related to higher probability, whereas diabetes, heart failure, chronic kidney disease, chronic obstructive pulmonary disease, ST-elevation myocardial infarction, and myocardial revascularization were related to lower probability of participation in the outpatient CR. Participation in outpatient CR was related to the risk of all-cause mortality both in univariable (hazard ratio [95% confidence intervals] 0.37 [0.26-0.51]) and multivariable analysis (0.53 [0.38-0.74]). Participation in the outpatient CR was also related to the lower risk of death or MI or stroke (0.57 [0.48-0.67] and 0.72 [0.61-0.84]) and a lower risk of death or hospitalization due to cardiovascular reasons: 0.78 (0.73-0.84) and 0.85 (0.80-0.91) for the univariable and multivariable analyses respectively. The analysis of propensity score matched groups confirmed the results.

Conclusion

Outpatient CR following MI may be related to improved prognosis compared to the inpatient programme.

Luminescent Cationic Group 4 Metallocene Complexes Stabilized by Pendant N-Donor Groups

Cationic group 4 metallocene complexes with pendant imine and pyridine donor groups were prepared as stable crystalline [B(C₆F₅)₄]^- salts either by protonation of the intramolecularly bound ketimide moiety in neutral complexes [(η⁵-C₅Me₅){η⁵-C₅H₄CMe₂CMe₂C(R)═N-κN}MCl] (M = Ti, Zr, Hf; R = t-Bu, Ph) by PhNMe₂H⁺[B(C₆F₅)₄]^- to give [(η⁵-C₅Me₅){η⁵-C₅H₄CMe₂CMe₂C(R)═NH-κN}MCl]⁺[B(C₆F₅)₄]^- or by chloride ligand abstraction from the complexes [(η⁵-C₅Me₅)(η⁵-C₅H₄CMe₂CH₂C₅H₄N)MCl₂] (M = Ti, Zr) by Li[B(C₆F₅)₄]·2.5Et₂O to give [(η⁵-C₅Me₅)(η⁵-C₅H₄CMe₂CH₂C₅H₄N-κN)MCl]⁺[B(C₆F₅)₄]^-. Solid state structures of the new compounds were established by X-ray diffraction analysis, and their electrochemical behavior was studied by cyclic voltammetry. The cationic complexes of Zr and Hf, compared to the corresponding neutral species, exhibited significantly enhanced luminescence predominantly from triplet ligand-to-metal (³LMCT) excited states with lifetimes up to 62 μs and quantum yields up to 58% in the solid state. DFT calculations were performed to explain the structural features and optical and electrochemical properties of the complexes.

Managed care improves prognosis in acute myocardial infarction survivors. Data from the MAnaged Care for Acute Myocardial Infarction Survivors (MACAMIS) Programme

Background

Mortality following acute myocardial infarction (MI) remains high despite progress in pharmacotherapy and interventional treatment. In 2017 a nation-wide system of managed care for MI survivors comprising a continuum of acute treatment of MI, staged revascularization, cardiac rehabilitation, cardiac electrotherapy and cardiac ambulatory care within one year following MI was implemented in Poland. The managed care programme (MCP) includes also the quality of care assessment based on clinical measures (e.g. cardiovascular risk factors control) as well as on the rate of minor and major cardiovascular events. The goal of the analysis was to assess the overall mortality of MI survivors participating and not participating in the MCP.

Methods

The database of survivors of acute MI discharged from hospital from October 1, 2017 to December 31, 2018 was analyzed. Patients who died within 10 days after discharge were excluded from the analysis. The primary end-point was defined as death from any cause. Propensity-Score Matching (PSM) using nearest neighbor matching was used to form comparable groups of patients participating and not participating in the MCP. The Cox proportional hazard regression analysis was used to assess the relation between MCP and the overall mortality.

Results

MCP was implemented in the first stage in 48 hospitals spread around the country (about 34% of all hospitals treating acute MI patients in Poland). Out of 87739 analyzed patients (age: 68.1±11.9 years; 55581 men and 32158 women) 34064 were hospitalized in hospitals with MCP implemented. Altogether 10404 patients (11.9% of the whole cohort; 30.5% of those hospitalized in hospitals with MCP implemented) participated in MCP. They were matched with 10404 patients not participating in the MCP. During 324.8±140.5 days of follow-up 7413 patients died. One-year mortality was lower in patients participating in the MCP both when we analyzed the whole cohort (4.4% vs. 9.5%; p<0.001) as well as when we limited the analysis to the PSM groups (4.4% vs. 6.5%; p<0.001, figure 1). MCP was related to the overall mortality in univariate (HR 0.43 [0.39–0.48]) as well as in multivariate analysis (0.64 [0.57–0.71]) in the whole cohort as well as in the PSM cohort (HR 0.63 [0.56–0.72] and 0.64 [0.56–0.72] for the univariate and multivariate analysis respectively). When we limited the analysis to hospitals in which MCP was implemented one-year mortality was 4.3% vs. 6.3% (p<0.001) whereas univariate HR was 0.51 (0.44–0.60) and multivariate HR 0.52 (0.44–0.61).

Conclusion

The implemented in Poland nation-wide system of managed care for MI survivors is related to improved survival. Therefore, the Ministry of Health plans to implement the programme in all cardiac centers in Poland.

Funding Acknowledgement

Type of funding source: None

Hydrodehalogenation of organohalides by Et3SiH catalysed by group 4 metal complexes and B(C6F5)3

The use of the Et₃SiH/B(C₆F₅)₃ system for the activation of group 4 metal catalysts allows the efficient and selective catalytic hydrodefluorination of trifluorotoluenes.

Ring Formation and Hydration Effects in Electron Attachment to Misonidazole

We study the reactivity of misonidazole with low-energy electrons in a water environment combining experiment and theoretical modelling. The environment is modelled by sequential hydration of misonidazole clusters in vacuum. The well-defined experimental conditions enable computational modeling of the observed reactions. While the NO 2 - dissociative electron attachment channel is suppressed, as also observed previously for other molecules, the OH - channel remains open. Such behavior is enabled by the high hydration energy of OH - and ring formation in the neutral radical co-fragment. These observations help to understand the mechanism of bio-reductive drug action. Electron-induced formation of covalent bonds is then important not only for biological processes but may find applications also in technology.

Hydrogenation of titanocene and zirconocene bis(trimethylsilyl)acetylene complexes

Reactions following the addition of dihydrogen under maximum atmospheric pressure to bis(trimethylsilyl)acetylene (BTMSA) complexes of titanocenes, [(η5-C5H5-nMen)2Ti(η2-BTMSA)] (n = 0, 1, 3, and 4) (1A-1D), and zirconocenes, [(η5-C5H5-nMen)2Zr(η2-BTMSA)] (n = 2-5) (4A-4D), proceeded in diverse ways and, depending on the metal, afforded different products. The former complexes lost, in all cases, their BTMSA ligand via its hydrogenation to bis-1,2-(trimethylsilyl)ethane when reacted at 80 °C for a prolonged reaction time. For n = 0, 1, and 3, the titanocene species formed in situ dimerised via the formation of fulvalene ligands and two bridging hydride ligands, giving known green dimeric titanocenes (2A-2C). For n = 4, a titanocene hydride [(η5-C5HMe4)2TiH] (2D) was formed, similarly to the known [(η5-C5Me5)2TiH] (2E) for n = 5; however, in contrast to this example, 2D in the absence of dihydrogen spontaneously dehydrogenated to the known Ti(iii)-Ti(iii) dehydro-dimer [{Ti(η5-C5HMe4)(μ-η1:η5-C5Me4)}2] (3B). This complex has now been fully characterised via spectroscopic methods, and was shown through EPR spectroscopy to attain an intramolecular electronic triplet state. The zirconocene-BTMSA complexes 4A-4D reacted uniformly with one hydrogen molecule to give Zr(iv) zirconocene hydride alkenyls, [(η5-C5H5-nMen)2ZrH{C(SiMe3)[double bond, length as m-dash]CH(SiMe3)}] (n = 2-5) (5A-5D). These were identified through their 1H and 13C NMR spectra, which show features typical of an agostically bonded proton, [double bond, length as m-dash]CH(SiMe3). Compounds 5A-5D formed equilibria with the BTMSA complexes 4A-4D depending on hydrogen pressure and temperature.