Lewis acid-base adducts of group 13 elements: synthesis, structure and reactivity toward benzaldehyde.

Lewis acid-base adducts [LGa-M(C6F5)3] (M = B 1, Al 2, Ga 3) were prepared by the reaction of gallanediyl LGa {L = HC[C(Me)N(2,6-i-Pr2C6H3)]2} with the Lewis acids M(C6F5)3 (M = B, Al, Ga). Benzaldehyde reacts with [LGa-M(C6F5)3] (M = B 1, Al 2) at room temperature with the insertion and formation of [LGa(C6F5){CH(Ph)(OB(C6F5)2)}] (4) and the zwitterionic species [LGa(C6F5){CH(Ph)(OAl(C6F5)2)}] (5), respectively, which was found to decompose at 80 °C with the formation of {(C6F5)2Al(OCH2Ph)}2 (6). Any attempts to isolate the insertion complex of [LGa-Ga(C6F5)3] with benzaldehyde failed and only {(C6F5)2Ga(OCH2Ph)}2 (7) was isolated at elevated temperatures. 2-5 and 7 were structurally characterized by heteronuclear NMR spectroscopy and single crystal X-ray diffraction.

Bonding situation in Be[N(SiMe3)2]2 ­ an experimental and computational study.

The solid state structure of Be[N(SiMe3)2]2 (1) was determined by in situ crystallisation and the bonding situation investigated by quantum chemical calculations. The Be-N bond is predominantly ionic, but some evidence for the presence of a partial Be-N double bond character was found.

Germane vs. digermane formation.

Oxidative addition reactions of dialkylchalcogenanes R2E2 and [Me2Si(Nt-Bu)2]Ge 1 yielded bis(alkylchalcogeno)germanes Me2Si(Nt-Bu)2Ge(ER)2 (R = Et, E = S 2, Se 3; R = Me, E = Se 4) and digermanes [Me2Si(Nt-Bu)2Ge(EEt)]2 (E = S 5, Se 6). The reaction of 1 with Et2Te2 proceeds with formation of Me2Si(Nt-Bu)2Ge(TeEt)27, which slowly converts into the Te-bridged complex [Me2Si(Nt-Bu)2GeTe]28. 1-6 and 8 were characterized by single crystal X-ray diffraction.

Sequential Bi-C bond activation reactions of BiEt3 via insertion reactions of RE {R = HC[C(Me)N(2,6-i-Pr2C6H3)]2; E = Al, Ga, In}.

Two of the Bi-C bonds of BiEt3 are sequentially activated by mono-valent RM {R = HC[C(Me)N(2,6-i-Pr2C6H3)]2; M = Al, Ga, In}. The first Bi-C bond activation leads to the formation of insertion complexes, [RMEt(BiEt2)] (M = Al 1; Ga 2; In 3), whereas the consecutive second activation proceeds through a reductive elimination of RMEt2 (M = Al 4, Ga 5), elemental Bi and BiEt3.

Unilateral empyema impacts the assessment of regional lung ventilation by electrical impedance tomography.

Several studies have shown the ability of electrical impedance tomography (EIT) to assess regional ventilation distribution in human lungs. Fluid accumulation in the pleural space as in empyema, typically occurring on one chest side, may influence the distribution of ventilation and the corresponding EIT findings. The aim of our study was to examine this effect on the assessment of regional ventilation by EIT. Six patients suffering from unilateral empyema and intubated with a double-lumen endotracheal tube were studied. EIT data were acquired during volume-controlled ventilation with bilateral (tidal volume (V(T)): 800 ml) and unilateral ventilation (V(T): 400 ml) of the right and left lungs. Mean tidal amplitudes of the EIT signal were calculated in all image pixels. The sums of these values, expressed as relative impedance change (rel. ΔZ), were then determined in whole images and functionally defined regions-of-interest (ROI). The sums of rel. ΔZ calculated during the two cases of one-lung ventilation either on the affected or unaffected side were significantly smaller than during bilateral ventilation. However, in contrast to previous findings in patients with no pleural pathology, very low values of rel. ΔZ were found when the lung on the affected side was ventilated. ROI-based analysis rendered higher values than the whole-image analysis in this case, nonetheless, the values were significantly smaller than when the unaffected side was ventilated in spite of identical VT. In conclusion, our results indicate that the presence of empyema may affect the quantitative evaluation of regional lung ventilation by EIT.

Guideline for determining the mean glandular dose according to DIN 6868-162 and threshold contrast visibility according to the quality assurance guideline for digital mammography systems.

As part of the physico-technical quality assurance of the German breast cancer screening program, the threshold contrast visibility and the average glandular dose of every digital mammography system have to fulfill the requirements of the "European guidelines for quality assurance in breast cancer screening and diagnosis" (4th Edition). To accomplish uniform measurements in all federal states of Germany, the physical board of the reference centers developed a special guideline in 2009. Due to recent changes in the guidelines and standards, a second version of the guideline was developed by the reference centers. This guideline describes the determination of the average glandular dose as well as the CDMAM image acquisition and the CDMAM image evaluation. The determination of the threshold contrast visibility can be performed visually or automatically. The determination of the average glandular dose is based on DIN 6868 - 162 and the threshold contrast visibility test is based on the German "Quality Assurance Guideline".

Reactions of a Zn(I) complex with group 14 azides--formation of zinc azide and zinc hexazene complexes.

Two zinc hexazene complexes L2Zn2(l-1,6-R2-N6) (L = HC[C(Me)N-(2,4,6-Me3C6H2)]2; R = Ph (3), Dipp = 2,6-i-Pr2C6H3 (4)), were synthesized by reaction of the Zn(I) complex L2Zn2 (1) with phenyl azide and 2,6-diisopropylphenyl azide, respectively. 3 represents the second structurally characterized transition metal hexazene complex. In contrast, reactions of 1 with Me3MN3 (M = Si, Sn) yielded the azido complex [LZn(l-N3)]2 (2) and Me3M-MMe3.

Reaction of L2Zn2 with Ph2E2--synthesis of LZnEPh and reactions with oxygen and H-acidic substrates.

L2Zn2 (L = HC[C(Me)N(2,4,6-Me3C6H2)]2) and Ph2E2 (E = Se, Te) react to form LZnSePh (1) and LZnTePh (2).1 and 2 further react with H2O and EtOH to form LZnOH (3) and LZnOEt (4), respectively, whereas the reaction of 2 with oxygen yielded [LZnOTe(O)Ph]2 (5). 1, 4 and 5 were characterized by single crystal X-ray diffraction.

Parameter study for the finite element modelling of long bones with computed-tomography-imaging-based stiffness distribution.

Four radii of different horses were tested in three-point bending and in pure torsion. Detailed finite element (FE) models of these long bones were established by means of computed-tomography (CT) images and tests simulated for both load cases. For the allocation of the local isotropic material stiffness, individual exponential functions were applied whose factor and exponent were determined solely by fitting them to the measured torsional stiffness and bending stiffness of the entire bones. These stiffness functions referring directly to the CT number and having exponents between 1.5 and 2 were in good agreement with Young's moduli subsequently measured from small samples cut from the investigated bones. Based on a model with local orthotropic material definition, an additional parameter study was conducted to verify the sensitivities of the FE analysis results on single variations in the orthotropic elastic constants. This study revealed that the bending test simulations could be enhanced by substantial reduction in Young's moduli in the directions perpendicular to the bone axis; thus, orthotropic material definition is preferable for the FE analysis of long bones.

[Guideline for the additional test positions according to the EPQC 4th Edition for Digital Mammography Systems]. / Prüfanleitung für die Durchführung der ergänzenden Prüfpositionen nach EPQC 4th Edition für digitale Mammografie-Systeme.

Within the physical-technical quality assurance of the German breast cancer screening program all digital mammography systems have to perform the contrast resolution test and the determination of the average glandular dose based on the European guidelines for quality assurance in breast cancer screening and diagnosis (4th Edition). Since 1.1.2009 this applies to digital systems outside the screening program too. To accomplish uniform measurements in all federal states of Germany, the physical board of the reference centers developed together a special guideline for these test position. This Guideline describes the determination of the average glandular dose for different types of mammography systems, the CDMAM image acquisition and the CDMAM image evaluation as well. This guideline was verified by the German task group "Röntgenverordnung".

[Bavarian mammography screening program]. / Bayerisches Mammographiescreening (BMS).

In Bavaria since the 1st April 2003 we have been conducting a high quality mammography-screening carried out in individual practises (BMS). We have used the European and the S 3 guidelines. The best diagnosis is an early diagnosis of the breast carcinoma to save human life. Because of this and the high mortality rate due to this disease it is essential to have a mammogram screening program. There is no single one ideal way of constructing a screening program, it is always based on compromise within the particular health care-systems. Arising problems cannot be avoided, it is only possible when all parties work closely together that the BMS works properly.

[Bavarian mammography screening: results of consistency tests in X-ray units over three months]. / Ergebnisse aus drei Monaten Konstanzprüfung an Röntgeneinrichtungen im Bayerischen Mammographie-Screening.

PURPOSE: To find out whether the quality requirements in daily, weekly or monthly tests of the "European protocol for the quality control of the physical and technical aspects of mammographic screening (EPQC)" can be maintained when screening the population of a large area. Furthermore, to check the specific tolerances of different test positions given by the EPQC for redundancy and statistical correlation. MATERIALS AND METHODS: Daily test images were obtained with an additional exposition of a sensitometric step wedge according DIN 6868 - 2. Weekly densitometry and visual inspection were performed at the University of Applied Sciences, Cologne. RESULTS: All units were able to maintain basic requirements on image quality as long as films of the same batch number were used. Some tolerance requirements of the EPQC are inconsistent and redundant. CONCLUSION: The occasionally considerable fluctuations of film processing require a daily check on the processing conditions. Daily test images of the units are only obligatory in the first 4 to 5 weeks of a new operation. All test results should be analyzed retrospectively in an independent test laboratory with emphasis on the statistical behavior of the unit. The tolerances prescribed by the EPQC are not always consistent and should be adapted to today's scientific standard when applied in mammography screening centers.

Crystal engineering of primary cubanecarboxamides: Repetitive formation of an unexpected N-H...O hydrogen-bonded network.

The unusual N-H.O hydrogen bond pattern in a family of primary cubanecarboxamides is described. 4-Chloro-1-cubanecarboxamide, 1, and the corresponding bromo and iodo derivatives, 2 and 3, form the "shallow-glide" hydrogen-bonded motif instead of the usual 5.1 A translated ribbon pattern, more characteristic of primary amides. This behavior is also seen, somewhat unexpectedly, for cubanecarboxamide, 4, but more or less unsurprisingly for 1,4-cubanedicarboxamide, 5. This repetitive occurrence of the same hydrogen bond pattern is of significance in crystal engineering wherein synthon robustness is measured in terms of such repetitivity. The cubyl group is directly responsible for the appearance of the shallow-glide motif in this family in preference to the 5.1 A translation pattern for two reasons: (1) steric--it is too large to fit in a 5.1 A translated structure and (2) electronic--its carbon acidity is sufficient to result in the appearance of C-H.O hydrogen bonds to the C=O group, disrupting any putative 5.1 A translated structure. Such a molecule --> supermolecule relationship is of value in crystal engineering strategies.

Branched Star-Type Polysilyllithium Compounds: The Effects of ß-Silyl Substitution and of Complexation on Their Molecular Structure.

It was fortunate that the first extended branched polysilyl anion (Me3 SiMe2 Si)3 Si(-) could be crystallographically characterized in two forms-as the THF complex 1 and as the dimer 2. Comparison with the analogous (Me3 Si)3 SiLi systems 3 and 4 shows that ß-Me3 Si substitution and complexation by THF elongate the Si-Li distance by 0.09-0.14 Å and 0.04-0.07 Å, respectively.

Synthesis, spectroscopic, and structural properties of spirocyclopropanated bicyclobutylidenes and their radical cations.

The spirocyclopropanated bicyclobutylidenes 3-7 have been prepared by McMurry coupling of the corresponding spirocyclopropanated cyclobutanone (3 and 5), Staudinger-Pfenniger reaction (4), oxidative coupling of a Wittig ylide (4) or Wittig olefination of perspirocyclopropanated cyclobutanone (6 and 7). The structure of the parent 2a and the perspirocyclopropanated bicyclobutylidene 5 was determined by X-ray crystallography which disclosed considerable steric congestion around the double bond. As a result 5 did undergo addition of dichlorocarbene, epoxidation with meta-chloroperbenzoic acid, and cyclopropanation with CH2I2/ZnEt2, but did not add the more bulky dibromocarbene. The reaction of 5 with tetracyanoethene proceeded smoothly, but led to a formal [3+2] cycloadduct across the proximal single bond of one of the inner cyclopropane rings. The consecutive spirocyclopropanation of bicyclobutylidene led to a bathochromic shift in the UV spectra of 12 and 17nm, respectively, for each pair of beta- and alpha-spirocyclopropane groups. In the He(I)-photoelectron spectra of these bicyclobutylidenes, the effect of spirocyclopropanation upon their pi-ionization energies (pi-IE,) was found to be almost additive, leading to a lowering of 0.05 eV per any additional beta-spirocyclopropane, and 0.28-0.22 eV per additional alpha-spirocyclopropane group; this indicates an increasing nucleophilicity of the double bonds in the order 1 < 4 < 3 < 5. Following the radical cations of the three symmetrical bicyclobutylidenes without (2a, b) and with six (5) spiroannelated cyclopropane rings, the radical cations of two symmetrical bicyclobutylidenes with two (4) and four (3) such rings were studied by ESR spectroscopy. Whereas 2b.+, 3.+, and 5.+ could be generated by electrolytic oxidation of the corresponding hydrocarbons in solution, the spectra of 2a.+ and 4.+, with unsubstituted 2,2',4,4'-positions, were observed upon radiolysis of their neutral precursors in a Freon matrix. On going from 2a.+ to 4.+, the coupling constant [aH] of the eight beta protons in the 2,2',4,4'-positions of bicyclobutylidene increases from 2.62 to 3.08 mT, and that of the four gamma protons in the 3,3'-positions changes from 0.27 to 0.049 to 0.401 mT on passing from 2a.+ via 2b.+ to 3.+. Computations by means of the density functional theory (DFT) at the B3LYP/6-311+G*//B3LYP/6-31G* level reproduce well the experimental hyperfine data.

Programmed construction of discrete self-assembled cyclic aggregates

Examples for programmed self-assembly of alpha,beta-unsaturated ketoximes carrying a terminal pyridine subunit are described. The solid-state structures of a series of pyridinyl alpha,beta-unsaturated ketoximes 1 were investigated by X-ray structural analysis; this demonstrated that molecules 3-5 predictably form discrete cyclic aggregates stabilized by a network of hydrogen bonds and aromatic interactions.

Experimental and theoretical investigations on the synthesis, structure, reactivity, and bonding of the stannylene-iron complex Bis bis(2-tert-butyl-4,5,6-trimethyl-phenyl)SnFe (eta6-toluene) (Sn-Fe-Sn)

The pi-(arene)bis(stannylene) complex bis(bis(2-tert-butyl-4,5,6-trimethylphenyl)SnFe(eta6-toluene) (Sn-Fe-Sn, 15) is accessible in high yields by a metal-atom-mediated synthesis between iron atoms, toluene, and the stannylene [bis(2-tert-butyl-4,5,6-trimethylphenyl)Sn](3). Complex 15 has a half-sandwich structure with short Fe -Sn bonds (2.432(1) A) and a trigonal-planar coordination at both the Fe and Sn atoms. The distance between the two Sn centers is 3.56 A. Complex 15 is stable under ambient conditions and displays a pi-arene lability, so far rarely observed for (arene)iron complexes; this leads to an irreversible substitution of the arene and formation of fivefold-coordinated zerovalent iron complexes. The pi-arene lability of the title compound is a result of the Fe-Sn bonding situation, which can be interpreted, on the basis of an extended Huckel molecular orbital calculation, as being solely a donation of the 5sigma lone-pair of Sn into empty or half-filled acceptor d orbitals on Fe. As the calculations reveal, there is little backbonding from the iron to the tin, and the strong sigma donation leads to an increased occupation of the pi-antibonding orbitals of the eta6-arene, which are mainly responsible for the experimentally observed arene lability. Fe and Sn Mossbauer spectra support the polar character of Sn(sigma+)-->Fe(sigma-) with strong sigma donation from tin to iron, but significantly low iron-to-tin pi backdonation.

Synthesis, structure, and spectroelectrochemical investigation of novel ternary Co/S(Se)/Sn clusters derived from binary cobalt stannanediyl complexes.

The synthesis and structure of heterobimetallic Co/Sn complexes [(eta5-CpR)Co-Sn[CH(SiMe3)2]2] (CpR = C5Me5 2; C5EtMe4 3) are described. Insertion reactions of sulfur and selenium into the unbridged heteronuclear Co-Sn bonds of 1, 2, and 3 (R= H5 1, Me5 2, EtMe4 3) have been studied. Depending on the stoichiometry of the chalcogen element used, novel ternary Sn-chalcogen-Co clusters (8, 9, 15, and 16) can be synthesized, and their molecular structures, which represent rare examples of crystallographically characterized cases of ternary transition metal/chalcogen/tin complexes, have been determined. Electrochemistry shows that complexes 8 and 9 are able to support reversibly either the removal or addition of one electron. Insertion of a further (Cp)Co-E (E = chalcogen) fragment significantly affects the electron distribution and causes complexes 9 and 16 to undergo two consecutive one-electron oxidations. The EPR spectra of the respective monocations have been recorded. In all cases, the unpaired electron strongly interacts with the cobalt nucleus(i), thus testifying that the main contribution to the relevant HOMO orbitals comes from the cobalt atom(s).

Hexabromotricyclobutabenzene and hexabromohexaradialene: their nickel-mediated one-pot syntheses and crystal structure.

The reaction of hexakis(dibromomethyl)benzene with [(Bu3 P)2 -Ni(COD)] (COD = 1,5-cyclooctadiene) in DMF at 65-70°C yielded a mixture of the title compounds. The mixture was separated by column chromatography to yield hexabromotricyclobutabenzene (3 a) and hexabromohexaradialene (4) in 24 and 16% yields, respectively. (1) H and (13) C NMR spectroscopy suggest that 3 is obtained as the syn-all-trans isomer 3 a, and the symmetric anti-all-trans isomer 3 b is not obtained at all. The X-ray structures of 3 a and 4 are reported. The hexaradialene 4 has a chair conformation, and deviates from planarity by 43.6°. Heat or radical impurities cause the clean transformation of 3 a to 4.