Neuartige Boran- und Phosphoran-funktionalisierte anionische Carbenliganden

N-heterocyclic carbenes (NHC) are utilized for the stabilization of reactive compounds, for the activation of strong bonds, and as ligands in transition metal chemistry. In contrast to neutral NHCs, few examples of anionic or even dianionic NHCs are known. One approach for the synthesis of anionic carbenes is the deprotonation of neutral or anionic precursors, bearing Lewis acids instead of alkyl or aryl substituents. Following this strategy, novel anionic and dianionic NHCs, featuring weakly coordinating fluorinated borane and phosphorane substituents or coordinating tricyanoborane substituents were synthesized within the scope of this thesis. These carbenes possess unprecedented stabilities compared to related species. Furthermore, their electronic and steric properties can be directly adjusted by the type of Lewis acid attached. Their potential as ligands with highly shielding weakly coordinating substituents next to the carbene coordination center was demonstrated by the syntheses of the respective NHC selenium adducts and NHC gold(I) complexes. In contrast anionic NHCs with coordinating tricyanoborane moieties have an outstanding potential as ditopic ligands with coordination being possible at the carbene center and via the cyano groups. Their beneficial ligand properties were demonstrated by the syntheses of the respective NHC selenium adducts and NHC nickeltricarbonyl complexes. The combination of electronic properties, the large buried volume, the negative charge, the possibility to act as ditopic or ligands with weakly coordinating groups, and the ease of accessibility render borane- and phosphorane functionalized NHCs unique novel ligands. A further project of this PhD thesis deals with the steric properties of Lewis acids. Therefore, an easy-to-apply model was designed to quantify the steric demand of Lewis acids. Using the results of this evaluation, a second model was developed which judges the steric repulsion in Lewis acid/base adduct formation for arbitrary sets of acids and bases.N-heterozyklische Carbene (NHC) werden für die Stabilisierung reaktiver Verbindungen, für die Aktivierung starker Bindungen sowie als Liganden in der Übergangsmetallchemie eingesetzt. Im Gegensatz zu neutralen NHCs sind nur sehr wenige Vertreter anionischer oder gar dianionischer NHCs bekannt. Eine gute Strategie für deren Synthese stellt die Deprotonierung neutraler oder anionischer Vorstufen dar, welche Lewis-Säuren an Stelle von Alkyl- oder Arylsubstituenten tragen. Dieser Route folgend, wurden im Rahmen dieser Arbeit neue anionische und dianionische NHCs dargestellt, welche mit schwach koordinierenden, fluorierten Boran- und Phosphoransubstituenten oder mit koordinierenden Tricyanoboraneinheiten funktionalisiert sind. Diese Carbene besitzen beispiellose Stabilitäten, verglichen mit verwandten Verbindungen. Darüber hinaus können deren elektronischen und sterischen Eigenschaften direkt über die Wahl der Lewis-Säure gesteuert werden. Das Potential der Liganden mit stark abschirmenden schwach koordinierenden Substituenten in Nachbarschaft zum Carbenzentrum wurde durch die Synthese von NHC-Selen-Verbindungen sowie NHC-Gold(I)komplexen gezeigt. Im Gegensatz hierzu besitzen anionische NHCs mit koordinierenden Tricyanoboraneinheiten ein herausragendes Potential als ditope Liganden, da eine Koordination sowohl über das Carbenzentrum als auch über die Cyanogruppen möglich ist. Diese Vorteilhaften Ligandeneigenschaften wurden durch die Synthese entsprechender NHC-Selen-Addukte und NHC-Nickeltricarbonylkomplexe gezeigt. Somit macht die Kombination der elektronischen Eigenschaften, des großen verdeckten Volumens, der negativen Ladung, der Möglichkeit als ditoper Ligand oder als Ligand mit schwach koordinierenden Gruppen zu fungieren sowie die einfache Zugänglichkeit Boran- und Phosphoran-funktionalisierte NHCs zu einzigartigen neuartigen Liganden. Ein weiterer Teil dieser Arbeit setzt sich mit dem sterischen Anspruch von Lewis-Säuren auseinander. Hierfür wurde ein einfach anwendbares Modell entworfen, welches diesen quantifiziert. Ausgehend von diesen Ergebnissen wurde ein zweites Modell entwickelt, welches die sterische Abstoßung zwischen Lewis-Säure/Base-Addukten für beliebige Säure/Base-Kombinationen beurteilt

The crystal structure of poly[(μ 3_3-imidazolato-κ 3^3 N:N:N′)(tetrahydrofuran- κ 1^1 O)lithium(I)], C7_7H11_{11}LiN2_2O

C$_7$H$_{11}$LiN$_2$O, monoclinic, P2$_1$/c (no. 14), a = 8.9067(1) angstrom, b = 8.6975(1) angstrom, c = 10.2398(1) angstrom, beta = 101.900(3)degrees, V = 770.491(15) angstrom(3), Z = 4, R-gt (F) = 0.0338, wR(ref) (F$^2$) = 0.0925, T = 100 K

1,3-bis(tricyanoborane)imidazoline-2-ylidenate anion - a ditopic dianionic N-heterocyclic carbene ligand

The 1,3-bis(tricyanoborane)imidazolate anion 1 was obtained in high yield from lithium imidazolate and B(CN)$_3$−pyridine adduct. Anion 1 is chemically very robust and thus allowed the isolation of the corresponding H$_5$O$_2$$^+$ salt. Furthermore, monoanion 1 served as starting species for the novel dianionic N-heterocyclic carbene (NHC), 1,3-bis(tricyanoborane)imidazoline-2-ylidenate anion 3 that acts as ditopic ligand via the carbene center and the cyano groups at boron. First reactions of this new NHC 3 with methyl iodide, elemental selenium, and [Ni(CO)$_4$] led to the methylated imidazolate ion 4, the dianionic selenium adduct 5, and the dianionic nickel tricarbonyl complex 6. These NHC derivatives provide a first insight into the electronic and steric properties of the dianionic NHC 3. Especially the combination of properties, such as double negative charge, different coordination sites, large buried volume and good σ-donor and π-acceptor ability, make NHC 3 a unique and promising ligand and building block

Support pressure distribution for positioning in neutral versus conventional positioning in the prevention of decubitus ulcers: a pilot study in healthy participants

Abstract Background Decubitus ulcers are associated with a burden for the patients and cause enormous costs. One of the reasons for the development of decubitus is prolonged exposure to pressure. The aim of this pilot study was to examine the pressure distribution of healthy individuals either positioned in Positioning in Neutral (LiN) or conventional positioning (CON). Methods Four healthy participants were positioned in a supine, 30° degree side lying and 90° side lying position both in LiN and CON. A thousand pressure sensors in a mattress enabled a visual presentation of low, medium and high pressure on a screen. This presentation was processed by Photoshop in order to count the pixels representing the total support pressure surface and the pressure intensity. Results LiN showed, on average, a smaller surface with measurable pressure compared to CON (46,293 versus 64,090 pixels). The areas of medium pressure were comparable. Mean areas of low and high pressure were both smaller in LiN as compared to CON (low: 8315 versus 22,790 pixels; high: 3744 versus 7277 pixels). Conclusion The results of this pilot study indicate that LiN is suitable for pressure sore prophylaxis because LiN showed less support surface and less maximum pressure as compared to CON

Der Todt der beste und glücklichste Medicus, Als (Tit.) Herr Johann Adam Zapf/ Erb- und Gerichts-Herr zu Rohrbach/ Medicinæ Hochberühmter Doctor, und Hoch-Fürstl. Sächß. Hoch-meritirter Leib- und Hoff-Medicus in Weimar/ Sein ... Herr Vetter ... und wehrtester College, Den 10. Januarii dieses 1708ten Jahrs ... in der Kirche zu Rohrbach beygesetztet wurde ...

DER TODT DER BESTE UND GLÜCKLICHSTE MEDICUS, ALS (TIT.) HERR JOHANN ADAM ZAPF/ ERB- UND GERICHTS-HERR ZU ROHRBACH/ MEDICINÆ HOCHBERÜHMTER DOCTOR, UND HOCH-FÜRSTL. SÄCHSS. HOCH-MERITIRTER LEIB- UND HOFF-MEDICUS IN WEIMAR/ SEIN ... HERR VETTER ... UND WEHRTESTER COLLEGE, DEN 10. JANUARII DIESES 1708TEN JAHRS ... IN DER KIRCHE ZU ROHRBACH BEYGESETZTET WURDE ... Der Todt der beste und glücklichste Medicus, Als (Tit.) Herr Johann Adam Zapf/ Erb- und Gerichts-Herr zu Rohrbach/ Medicinæ Hochberühmter Doctor, und Hoch-Fürstl. Sächß. Hoch-meritirter Leib- und Hoff-Medicus in Weimar/ Sein ... Herr Vetter ... und wehrtester College, Den 10. Januarii dieses 1708ten Jahrs ... in der Kirche zu Rohrbach beygesetztet wurde ... ([1]

Tricyanoborane‐Functionalized Anionic N‐Heterocyclic Carbenes: Adjustment of Charge and Stereo‐Electronic Properties

The 1‐methyl‐3‐(tricyanoborane)imidazolin‐2‐ylidenate anion (2) was obtained in high yield by deprotonation of the B(CN)3‐methylimidazole adduct 1. Regarding charge and stereo‐electronic properties, anion 2 closes the gap between well‐known neutral NHCs and the ditopic dianionic NHC, the 1,3‐bis(tricyanoborane)imidazolin‐2‐ylidenate dianion (IIb). The influence of the number of N‐bonded tricyanoborane moieties on the σ‐donating and π‐accepting properties of NHCs was assessed by quantum chemical calculations and verified by experimental data on 2, IIb, and 1,3‐dimethylimidazolin‐2‐ylidene (IMe, IIa). Therefore NHC 2, which acts as a ditopic ligand via the carbene center and the cyano groups, was reacted with alkyl iodides, selenium, and [Ni(CO)$_{4}$] yielding alkylated imidazoles 3 and 4, the anionic selenium adduct 5, and the anionic nickel tricarbonyl complex 8, respectively. The results of this study prove that charge, number of coordination sites, buried volume (%V$_{bur}$) and σ‐donor and π‐acceptor abilities of NHCs can be effectively fine‐tuned via the number of tricyanoborane substituents

Tris(pentafluoroethyl)difluorophosphorane: a versatile fluoride acceptor for transition metal chemistry

Fluoride abstraction from different types of transition metal fluoride complexes [L$_n$MF] (M=Ti, Ni, Cu) by the Lewis acid tris(pentafluoroethyl)difluorophosphorane (C$_2$F$_5$)$_3$PF$_2$ to yield cationic transition metal complexes with the tris(pentafluoroethyl)trifluorophosphate counterion (FAP anion, [(C$_2$F$_5$)$_3$PF$_3$]$^-$) is reported. (C$_2$F$_5$)$_3$PF$_2$ reacted with trans-[Ni(iPr$_2$Im)$_2$(Ar$^F$)F] (iPr2Im=1,3-diisopropylimidazolin-2-ylidene; Ar$^F$=C$_6$F$_5$, 1 a; 4-CF$_3$-C$_6$F$_4$, 1 b; 4-C$_6$F$_5$-C$_6$F$_4$, 1 c) through fluoride transfer to form the complex salts trans-[Ni(iPr$_2$Im)$_2$(solv)(Ar$^F$)]FAP (2 a-c[solv]; solv=Et$_2$O, CH$_2$Cl$_2$, THF) depending on the reaction medium. In the presence of stronger Lewis bases such as carbenes or PPh$_3$, solvent coordination was suppressed and the complexes trans-[Ni(iPr$_2$Im)$_2$(PPh$_3$)(C$_6$F$_5$)]FAP (trans-2 a[PPh$_3$]) and cis-[Ni(iPr$_2$Im)$_2$(Dipp$_2$Im)(C$_6$F$_5$)]FAP (cis-2 a[Dipp$_2$Im]) (Dipp$_2$Im=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were isolated. Fluoride abstraction from [(Dipp$_2$Im)CuF] (3) in CH$_2$Cl$_2$ or 1,2-difluorobenzene led to the isolation of [{(Dipp$_2$Im)Cu}$_2$]$^2$$^+$2 FAP$^-$ (4). Subsequent reaction of 4 with PPh$_3$ and different carbenes resulted in the complexes [(Dipp$_2$Im)Cu(LB)]FAP (5 a–e, LB=Lewis base). In the presence of C6Me6, fluoride transfer afforded [(Dipp$_2$Im)Cu(C$_6$Me$_6$)]FAP (5 f), which serves as a source of [(Dipp$_2$Im)Cu)]$^+$. Fluoride abstraction of [Cp$_2$TiF$_2$] (7) resulted in the formation of dinuclear [FCp$_2$Ti(μ-F)TiCp$_2$F]FAP (8) (Cp=η$^5$-C$_5$H$_5$) with one terminal fluoride ligand at each titanium atom and an additional bridging fluoride ligand

NHC induced radical formation via homolytic cleavage of B–B bonds and its role in organic reactions

International audienceBis-NHC adducts of the type (NHC) 2 ·B 2 (OR) 4 are sources of boryl radicals of the type NHC–BR 2 ˙, which are formed by homolytic B–B bond cleavage

Economic impact of heart failure with preserved ejection fraction: insights from the ALDO‐DHF trial

Aims Although heart failure (HF) with preserved ejection fraction (HFpEF) is a leading cause for hospitalization, its overall costs remain unclear. Therefore, we assessed the health care-related costs of ambulatory HFpEF patients and the effect of spironolactone. Methods and results The aldosterone receptor blockade in diastolic HF trial is a multicentre, prospective, randomized, double-blind, placebo-controlled trial conducted between March 2007 and April 2011 at 10 sites in Germany and Austria that included 422 ambulatory patients [mean age: 67 years (standard deviation: 8); 52% women]. All subjects suffered from chronic New York Heart Association (NYHA) class II or III HF and preserved left ventricular ejection fraction of 50% or greater. They also showed evidence of diastolic dysfunction. Patients were randomly assigned to receive 25 mg of spironolactone once daily (n = 213) or matching placebo (n = 209) with 12 months of follow-up. We used a single-patient approach to explore the resulting general cost structure and included medication, number of general practitioner and cardiologist visits, and hospitalization in both acute and rehabilitative care facilities. The average annual costs per patient in this cohort came up to euro1, 118 (± 2,475), and the median costs were euro332. We confirmed that the main cost factor was hospitalization and spironolactone did not affect the overall costs. We identified higher HF functional class (NYHA), male patients with low haemoglobin level, with high oxygen uptake (VO(2)max) and coronary artery disease, hyperlipidaemia, and atrial fibrillation as independent predictors for higher costs. Conclusions In this relatively young, oligosymptomatic, and with regard to the protocol without major comorbidities patient cohort, the overall costs are lower than expected compared with the HFrEF population. Further investigation is needed to investigate the impact of, for example, comorbidities and their effect over a longer period of time. Simultaneously, this analysis suggests that prevention of comorbidities are necessary to reduce costs in the health care system