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A complex of a metal in its zero oxidation state can be considered a stabilized, but highly reactive, form of a single metal atom. Such complexes are common for the more noble transition metals. Although rare examples are known for electronegative late-main-group p-block metals or semimetals.sup.1-6, it is a challenge to isolate early-main-group s-block metals in their zero oxidation state.sup.7-11. This is directly related to their very low electronegativity and strong tendency to oxidize. Here we present examples of zero-oxidation-state magnesium (that is, magnesium(0)) complexes that are stabilized by superbulky, monoanionic, [beta]-diketiminate ligands. Whereas the reactivity of an organomagnesium compound is typically defined by the nucleophilicity of its organic groups and the electrophilicity of Mg.sup.2+ cations, the Mg.sup.0 complexes reported here feature electron-rich Mg centres that are nucleophilic and strongly reducing. The latter property is exemplified by the ability to reduce Na.sup.+ to Na.sup.0. We also present a complex with a linear Mg.sub.3 core that formally could be described as a Mg.sup.I-Mg.sup.0-Mg.sup.I unit. Such multinuclear mixed-valence Mg.sub.n clusters are discussed as fleeting intermediates during the early stages of Grignard reagent formation. Their remarkably strong reducing power implies a rich reactivity and application as specialized reducing agents. Strongly reducing [beta]-diketiminate complexes containing magnesium in its zero oxidation state are reported, among which is a compound with a linear triatomic Mg-Mg-Mg core., Author(s): B. Rösch [sup.1] , T. X. Gentner [sup.1] , J. Eyselein [sup.1] , J. Langer [sup.1] , H. Elsen [sup.1] , S. Harder [sup.1] Author Affiliations: (1) Department of [...]

Here we report that attempted preparation of low-valent CaI complexes in the form of LCa-CaL (where L is a bulky b-diketiminate ligand) under dinitrogen (N2) atmosphere led to isolation of LCa(N2)CaL, which was characterized crystallographically. The N2 2ˉ anion in this complex reacted in most cases as a very potent two-electron donor. Therefore, LCa(N2)CaL acts as a synthon for the low-valent CaI complex LCa-CaL, which was the target of our studies. The N2 2ˉ anion could also be protonated to diazene (N2H2) that disproportionated to hydrazine and N2. The role of Ca d orbitals for N2 activation is discussed. [ABSTRACT FROM AUTHOR]

DFT-Calculations predict that a low-valent complex (BDI)Mg-Ca(BDI) with bulky β-diketiminate (BDI) ligands is thermodynamically stable. It was attempted to isolate such a complex by salt-metathesis between [( DIPeP BDI*)Mg - Na + ] 2 and [( DIPeP BDI)CaI] 2 ( DIPeP BDI = HC[C(Me)N-DIPeP] 2 ; DIPeP BDI* = HC[C( t Bu)N-DIPeP] 2 ; DIPeP = 2,6-CH(Et) 2 -phenyl). Whereas in alkane solvents no reaction was observed, salt-metathesis in C 6 H 6 led to immediate C-H activation of benzene to give ( DIPeP BDI*)MgPh and ( DIPeP BDI)CaH, the latter crystallizing as a THF-solvated dimer [( DIPeP BDI)CaH·THF] 2 . Calculations suggest reduction and insertion of benzene in the Mg-Ca bond. The activation enthalpy for the subsequent decomposition of C 6 H 6 2- into Ph - and H - is only 14.4 kcal mol -1 . Repeating this reaction in the presence of naphthalene or anthracene led to heterobimetallic complexes in which naphthalene 2- or anthracene 2- anions are sandwiched between ( DIPeP BDI*)Mg + and ( DIPeP BDI)Ca + cations. These complexes slowly decompose to their homometallic counterparts and further decomposition products. Complexes in which naphthalene 2- or anthracene 2- anions are sandwiched between two ( DIPeP BDI)Ca + cations were isolated. The low-valent complex ( DIPeP BDI*)Mg-Ca( DIPeP BDI) could not be isolated due to its high reactivity. There is, however, strong evidence that this heterobimetallic compound is a fleeting intermediate., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Complex [( DIPeP BDI)Ca] 2 (C 6 H 6 ), with a C 6 H 6 2- dianion bridging two Ca 2+ ions, reacts with benzene to yield [( DIPeP BDI)Ca] 2 (biphenyl) with a bridging biphenyl 2- dianion ( DIPeP BDI=HC[C(Me)N-DIPeP] 2 ; DIPeP=2,6-CH(Et) 2 -phenyl). The biphenyl complex was also prepared by reacting [( DIPeP BDI)Ca] 2 (C 6 H 6 ) with biphenyl or by reduction of [( DIPeP BDI)CaI] 2 with KC 8 in presence of biphenyl. Benzene-benzene coupling was also observed when the deep purple product of ball-milling [( DIPP BDI)CaI(THF)] 2 with K/KI was extracted with benzene (DIPP=2,6-CH(Me) 2 -phenyl) giving crystalline [( DIPP BDI)Ca(THF)] 2 (biphenyl) (52 % yield). Reduction of [( DIPeP BDI)SrI] 2 with KC 8 gave highly labile [( DIPeP BDI)Sr] 2 (C 6 H 6 ) as a black powder (61 % yield) which reacts rapidly and selectively with benzene to [( DIPeP BDI)Sr] 2 (biphenyl). DFT calculations show that the most likely route for biphenyl formation is a pathway in which the C 6 H 6 2- dianion attacks neutral benzene. This is facilitated by metal-benzene coordination., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Since the seminal report on Mg in the +I oxidation state in 2007, low-valent complexes featuring a Mg I -Mg I bond developed from trophy molecules to state-of-the-art reducing agents. Despite increasing interest in low-valency of the other group 2 metals, this area was restricted for a long time to a rare example of a Ca I (arene)Ca I inverse sandwich. This feature article focuses on the most recent developments in the field, highlighting recent breakthroughs for Be, Mg and Ca. The more exotic metal Be was the first to be isolated as a zero-valent complex which could be oxidized to a Be I species. There also has been interest in breaking the Mg I -Mg I bond with superbulky β-diketiminate ligands (BDI) that suppress (BDI)Mg-Mg(BDI) bond formation. This led to Mg-Mg bond elongation or Mg-N bond cleavage. Several reports on attempts to isolate (BDI)Mg˙ radicals by combinations of ligand bulk, addition of neutral ligands or UV(vis) irradiation led to reduction of the aromatic solvents, underscoring the high reactivity of these open shell species. Only recently, zero-valent complexes of Mg were introduced. Double reduction of a (BDI)MgI complex with Na gave [(BDI)Mg - ]Na + . This Mg 0 complex crystallized as a dimer in which the Na + cations bridge the two (BDI)Mg - anions which react as Mg nucleophiles. Thermal decomposition led to spontaneous formation of Na 0 and a trinuclear (BDI)MgMgMg(BDI) complex. This mixed-valence Mg 3 -complex is a prime example of the fleeting multinuclear Mg n intermediates discussed on the way from Mg metal to Grignard reagent. Attempts to prepare low-valent Ca I compounds by reduction of (BDI)CaI led to dearomatization of the arene solvents: (BDI)Ca(arene)Ca(BDI). Reduction in alkanes prevented this decomposition pathway but led to N 2 reduction and isolation of (BDI)Ca(N 2 )Ca(BDI), representing the first example of molecular nitrogen fixation with an early main group metal. As the N 2 2- anion reacts in most cases as a very strong two-electron reductant, LCa(N 2 )CaL could be seen as a synthon for hitherto elusive Ca I -Ca I complexes. Theoretical calculations suggest that participation of Ca d-orbitals is relevant for N 2 activation. These most recent developments in low-valent group 2 metal chemistry will revive this area and undoubtly lead to new reactivities and applications.

Spheroids are a promising tool for many cell culture applications, but their microscopic analysis is limited. Flow cytometry on a single cell basis, which requires a gentle but also efficient dissociation of spheroids, could be an alternative analysis. Mono-culture and coculture spheroids consisting of human fibroblasts and human endothelial cells were generated by the liquid overlay technique and were dissociated using AccuMax as a dissociation agent combined with gentle mechanical forces. This study aimed to quantify the number of apoptotic and proliferative cells. We were able to dissociate spheroids of differing size, age, and cellular composition in a single-step dissociation protocol within 10 min. The number of single cells was higher than 95% and in most cases, the viability of the cells after dissociation was higher than 85%. Coculture spheroids exhibited a higher sensitivity as shown by lower viability, higher amount of cellular debris, and a higher amount of apoptotic cells. Considerable expression of the proliferation marker Ki67 could only be seen in 1-day-old spheroids but was already downregulated on Day 3. In summary, our dissociation protocol enabled a fast and gentle dissociation of spheroids for the subsequent flow cytometric analysis. The chosen cell type had a strong influence on cell viability and apoptosis. Initially high rates of proliferative cells decreased rapidly and reached values of healthy tissue 3 days after generation of the spheroids. In conclusion, the flow cytometry of dissociated spheroids could be a promising analytical tool, which could be ideally combined with microscopic techniques., (© 2021 The Authors. Cell Biology International published by John Wiley & Sons Ltd on behalf of International Federation of Cell Biology.)

The bulk of a recently reported superbulky β-diketiminate ligand was further increased by introducing tBu substituents in the ligand backbone. Attempts to isolate free Mg radicals with this extremely bulky ligand failed. Instead, a dinuclear Mg(i) complex with one chelating and one monodentate β-diketiminate ligand was isolated. Asymmetry in metal coordination results in a polarized Mg-Mg bond.

Key to the isolation of the first alkyl strontium complex was the synthesis of a strontium hydride complex that is stable towards ligand exchange reactions. This goal was achieved by using the super bulky β-diketiminate ligand DIPeP BDI (CH[C(Me)N-DIPeP] 2 , DIPeP=2,6-diisopentylphenyl). Reaction of DIPeP BDI-H with Sr[N(SiMe 3 ) 2 ] 2 gave ( DIPeP BDI)SrN(SiMe 3 ) 2 , which was converted with PhSiH 3 into [( DIPeP BDI)SrH] 2 . Dissolved in C 6 D 6 , the strontium hydride complex is stable up to 70 °C. At 60 °C, H-D isotope exchange gave full conversion into [( DIPeP BDI)SrD] 2 and C 6 D 5 H. Since H-D exchange with D 2 is facile, the strontium hydride complex served as a catalyst for the deuteration of C 6 H 6 by D 2 . Reaction of [( DIPeP BDI)SrH] 2 with ethylene gave [( DIPeP BDI)SrEt] 2 . The high reactivity of this alkyl strontium complex is demonstrated by facile ethylene polymerization and nucleophilic aromatic substitution with C 6 D 6 , giving alkylated aromatic products and [( DIPeP BDI)SrD] 2 ., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The steric bulk of the well-known DIPP BDI ligand (CH[C(CH 3 )N-DIPP] 2 , DIPP=2,6-diisopropylphenyl) was increased by replacing isopropyl for isopentyl groups. This very bulky DIPeP BDI ligand could not stabilize the radical species ( DIPeP BDI)Mg . : reduction of ( DIPeP BDI)MgI with Na gave ( DIPeP BDI) 2 Mg 2 with a rather long Mg-Mg bond of 3.0513(8) Å. Addition of TMEDA prior to reduction gave complex ( DIPeP BDI) 2 Mg 2 (C 6 H 6 ), which could also be obtained as its THF adduct. It is speculated that combination of a bulky spectator ligand and TMEDA prevents dimerization of the intermediate Mg I radical, which then reacts with the benzene solvent. Complex ( DIPeP BDI) 2 Mg 2 (C 6 H 6 ), which formally contains the anti-aromatic anion C 6 H 6 2- , reacted with tBuOH as a Brønsted base to 1,3- and 1,4-cyclohexadiene and with H 2 as a two electron donor to ( DIPeP BDI) 2 Mg 2 H 2 and C 6 H 6 . It also reductively cleaved the C-F bond in fluorobenzene and gave ( DIPeP BDI)MgPh, ( DIPeP BDI)MgF, and C 6 H 6 ., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Alkaline earth metal amides (AeN'' 2 : Ae=Ca, Sr, Ba, N''=N(SiMe 3 ) 2 ) catalyze alkene hydrogenation (80-120 °C, 1-6 bar H 2 , 1-10 mol % cat.), with the activity increasing with metal size. Various activated C=C bonds (styrene, p-MeO-styrene, α-Me-styrene, Ph 2 C=CH 2 , trans-stilbene, cyclohexadiene, 1-Ph-cyclohexene), semi-activated C=C bonds (Me 3 SiCH=CH 2 , norbornadiene), or non-activated (isolated) C=C bonds (norbornene, 4-vinylcyclohexene, 1-hexene) could be reduced. The results show that neutral Ca or Ba catalysts are active in the challenging hydrogenation of isolated double bonds. For activated alkenes (e.g. styrene), polymerization is fully suppressed due to fast protonation of the highly reactive benzyl intermediate by N''H (formed in the catalyst initiation). Using cyclohexadiene as the H source, the first Ae metal catalyzed H-transfer hydrogenation is reported. DFT calculations on styrene hydrogenation using CaN'' 2 show that styrene oligomerization competes with styrene hydrogenation. Calculations also show that protonation of the benzylcalcium intermediate with N''H is a low-energy escape route, thus avoiding oligomerization., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Objective: To determine whether the accuracy of transvaginal sonography to detect endometrial pathology is enhanced by assessing endometrial morphology and the regularity of the endometrial border in addition to measurement of endometrial thickness in women with postmenopausal bleeding., Design and Methods: A total of 159 women with postmenopausal bleeding were included in a prospective study performed at the Clinic of Obstetrics and Gynecology, University of Mainz. The results obtained on transvaginal sonographic assessment of the endometrium were compared with the histological evaluation of the operative endometrial specimen., Results: A cut-off level for endometrial thickness of 5 mm had a sensitivity of 94%, specificity of 48% and positive and negative predictive values of 69% and 87%, respectively for the presence of endometrial pathology. Assessment of the regularity of the endometrial border showed a sensitivity of 75%, specificity of 66% and positive and negative predictive values of 73% and 69%, respectively. For the third sonographic parameter, endometrial morphology, the sensitivity was 82%, specificity 64%, the positive predictive value 73% and the negative predictive value 74%. The combined consideration of the three sonographic parameters showed a sensitivity of 97%, specificity of 65%, and positive and negative predictive values of 80% and 94%, respectively., Conclusion: The combined evaluation of endometrial thickness, endometrial morphology and the endometrial border enhances the accuracy of transvaginal sonography to detect endometrial pathology in women with postmenopausal bleeding, thus facilitating the decision regarding further diagnostic and therapeutic measures.

We report on a 45-year old patient who was treated for IgA-Nephritis for 9 months. During treatment he developed coughing and dyspnoea which led to diagnose a central stenosing NSCLC at the tracheobronchial angle. Cancer treatment by x-ray showed a good response, e.g. significant reduction of cancer volume and a remarkably improved renal function. In the course of tumour progression (3 months after initial treatment) retention parameter deteriorated again and the patient needed to be dialysed. Palliative laser therapy had no influence on renal function. The close linkage between tumour regression and the extent of IgA nephritis suggest that the preceding IgA nephritis was paraneoplastic and hence a primary symptom of the NSCLC.

We report 313 cases of osteosynthesis seen between 1977 and 1987 in our hospital. In 50 cases wound infection occurred and in 4 cases osteomyelitis. Important factors in the development of wound infection are soft tissue damage, duration of operation, time from accident to operation, and operation at night. The 4 cases of osteomyelitis occurred in patients who had undergone previous operations. All wound infections healed with local therapy and systemic antibiotics; the cases of osteomyelitis required surgical intervention and systemic antibiotics. No late defects or complications were seen in any case.

Experimental reproduction of necrotising enteritis of sucking pigs was successfully achieved by using both Clostridium perfringens Type C strains, which had been isolated from sucking pigs with necrotising enteritis, and Type C strain 3628 of A.T.C.C. (sub-type C1). The lethal dose for sucking pigs was between 20 X 10(6) and 12 X 10(7) pathogens per animal. The disease could not even be induced by repeated application of no-bacterial toxin of Cl. perfringens Type C nor by administration of Cl. perfringens Type A strains which had been cultured from broilers with necrotising enteritis. Necrotising enteritis was found to develop in two phases in sucking pigs. First, the pathogen will deposit to the villous epithelium and then penetrate the superficial strata of the mocous membrane. In the second phase, the villous structure will be destroyed by the lethal, haemolysing, and necrotising toxins of Cl. perfringens. The role played by individual toxin fractions is discussed together with the importance of humoral and localised infection defence. Sucking pigs may be sufficiently protected against infection based on single or ten-fold lethal infectious dosage by two vaccinations of the mother animal, five and three weeks prior to parturition, using "Enterotoxaemia Vaccine Dessau bivalent". Infection then would not occur unless a hundredfold lethal dose was applied. Characteristics include diarrhoea, apathy, exhaustion, and death.