Reactivity of mono- And divalent aluminium compounds towards group 15 nanoparticles

Herein, we present a novel approach towards organometallic group 13/15-compounds, i.e. the reaction of nanoparticular arsenic and antimony with low-valent aluminium species. The reaction of the two-electron reducing agent [AlCp*]$_{4}$ (Cp* = C$_{5}$Me$_{5}$) with arsenic nanoparticles gave rise to a mixture of two unprecedented deca- and dodecanuclear Al–As clusters. In contrast, the analogous transformation with nanoparticular antimony yielded the already known Al–Sb compound [(AlCp*)$_{3}$Sb$_{2}$]. Additionally, two different dialanes [AlCp*X]$_{2}$ (X = Br, I) were employed as one-electron reducing agents, forming calix like coordination compounds upon reaction with nano arsenic. The isolated species significantly enlarge the accessible structural variety of molecular group 13/15 compounds, highlighting the exceptional utility and reactivity of nanoscale group 15 precursors

Low-coordinate iridium NHC complexes derived from selective and reversible C–H bond activation of fluoroarenes

Interaction of the reactive 14 VE {Ir(IBioxMe4)3}+ fragment with fluoroarenes results exclusively in ortho-C–H bond oxidative addition and formation of 16 VE Ir(III) derivatives [Ir(IBioxMe4)3(Ar)H]+ (Ar = 2-C6H4F, 2,3-C6H3F2, 2,4,6-C6H2F3). The C–H bond activation reactions occur under mild conditions and are reversible

The Relationship between Levels of PCBs and Pesticides in Human Hair and Blood: Preliminary Results

Human hair as a biologic measure of exposure to persistent organic pollutants (POPs) has some advantages over the more commonly used blood and adipose tissue samples. However, one of the primary limitations is the difficulty in distinguishing between exogenous and endogenous contamination. In addition, there are currently no standardized methods for hair sample collection, washing, and chemical analysis. There is also very limited information describing the correlation between levels of organic contaminants in hair and other body compartments. To explore levels of POPs in blood and hair, samples from 10 volunteers were collected and analyzed for select organochlorine pesticides and 57 individual polychlorinated biphenyl (PCB) congeners. We demonstrated that the method for analyzing organic contaminants in human hair was reliable and reproducible. Washing hair with shampoo decreased levels of PCBs, pesticides, and lipids by 25–33% on average and up to 62% for low-chlorinated congeners. The percentage of lipids and the levels of organochlorines in hair were higher than in serum. We found strong correlation (r = 0.8) between p,p′-DDE (dichlorodiphenyldichloroethylene) levels in hair and blood and moderate correlations for the more persistent PCB congeners, but no correlations or weak correlations for other organochlorines. The present study provides preliminary evidence on the utility of hair analysis for POPs; however, further larger studies are recommended before hair analysis can be successfully applied in epidemiologic studies on POPs

C–F bond activation of perfluorinated arenes by a bioxazoline-derived N-heterocyclic carbene

The N-heterocyclic carbene IBioxMe4 enacts selective single and double C–F bond activation of octafluorotoluene and hexafluorobenzene, respectively. The formation of the fluoroarene substituted, zwitterionic imidazoliumolate products is consistent with a mechanism involving nucleophilic aromatic substitution and subsequent oxazoline ring opening by liberated fluoride

From a nanoparticular solid-state material to molecular organo-f-element-polyarsenides

A convenient pathway to new molecular organo-lanthanide-polyarsenides in general and to a f-element complex with the largest polyarsenide ligand in detail is reported. For this purpose, the activation of the solid state material As$^{0}$$_{nano}$ (nanoscale gray arsenic) by the multi electron reducing agents [K(18-crown-6)][(Image Cp\u27\u27$_{2}$ Ln$^{+II}$)$_{2}$(μ-η$^{6}$:η$^{6}$-C$_{6}$H$_{6}$)] (Ln = La, Ce, Cp′′ = 1,3-bis(trimethylsilyl)cyclopentadienyl anion) and [K(18-crown-6)]$_{2}$[(Cp\u27\u27$_{2}$Ln$^{+II}$)$_{2}$(μ-η$^{6}$:η$^{6}$-C$_{6}$H$_{6}$)] (Ln = Ce, Nd) is shown. These non-classical divalent lanthanide compounds were used as three and four electron reducing agents where the product formation can be directed by variation of the applied reactant. The obtained Zintl anions As$_{3}$$^{3-}$, As$_{7}$$^{3-}$, and As$_{14}$$^{4-}$ were previously not accessible in molecular 4f-element chemistry. Additionally, the corresponding compounds with As$_{14}$$^{4-}$-moieties represent the largest organo-lanthanide-polyarsenides known to date

UV-light promoted C–H bond activation of benzene and fluorobenzenes by an iridium(i) pincer complex

Iridium(I) carbonyl complex [Ir(2,6-(PtBu2CH2)2C6H3)(CO)] undergoes reversible C–H bond activation of benzene and a series of fluorobenzenes on UV irradiation. Exclusive ortho-selectivity is observed in reactions of fluorobenzene and 1,2-difluorobenzene

The Archetypal Homoleptic Lanthanide Quadruple-Decker—Synthesis, Mechanistic Studies, and Quantum Chemical Investigations

The synthesis of the first well-defined neutral and homoleptic (same metal, same ligand) all-carbon-based quadruple-decker complexes [Sm$^{III/II/III}$$_{3}$(COT$^{1,4-SiiPr3}$)$_{4}$] (COT$^{1,4-SiiPr3}$=1,4-($^{i}$Pr$_{3}$Si)$_{3}$C$_{8}$H$_{6}$)) along with other unique sandwich complexes is shown. Reduction of [Sm$^{III}$(COT$^{1,4-SiiPr3}(BH$$_{4}$)(thf)] (COT$^{1,4-SiiPr3}$=1,4-($^{i}$Pr$_{3}$Si)$_{3}$C$_{8}$H$_{6}$) with KC$_{8}$ resulted in [Sm$^{III/II/III}$$_{3}$(COT$^{1,4-SiiPr3}$)$_{4}$] the first example of a homoleptic lanthanide quadruple-decker. As indicated by an analysis of the bond metrics in the solid-state, the inner Sm ion is present in the divalent oxidation state, while the outer ones are trivalent. This observation could be confirmed by quantum chemical calculations. Mechanistic studies revealed not only insight into possible formation pathways of [Sm$^{III/II/III}$$_{3}$(COT$^{1,4-SiiPr3}$)$_{4}$] but also resulted in the transformation to other mixed metal sandwich complexes with unique structural properties. These are the 1D-polymeric chain structured [KSm$^{III}$(COT$^{1,4-SiiPr3}$)$_{4}$]$_{n}$ and the hexametallic species [(tol)K(COT$^{1,4-SiiPr3}$)Sm$^{II}$COT$^{1,4-SiiPr3}$)K]$_{2}$ which were initially envisioned as possible building blocks as part of different retrosynthetically guided pathways that we developed

Silole and germole complexes of lanthanum and cerium

Using dianionic metallole ligands (silole or germole) and the cyclooctatetraendiide dianion, heteroleptic lanthanide multi-decker complexes have been prepared. Due to the heteroatom of the metallole ligands intermolecular bridging between the sandwich complexes takes place. Our work highlights that different combinations of the lanthanide and heterocycle lead to different intermolecular interactions including a dimeric La-silole sandwich complex, a La-germole ladder-type polymeric species and a Ce-germole coordination polymer

Comparison of the immediate effects of gaseous ozone and chlorhexidine gel on bacteria in cavitated carious lesions in children in vivo

Clinical application of ozone gas has been shown to arrest the progression of dentinal caries in children. In this study, we compare the immediate effects of gaseous ozone and chlorhexidine gel on bacteria in cavitated carious lesions in children. Forty children, each with at least two open occlusal carious lesions, were enrolled in the study. Two teeth were chosen randomly. In one lesion, overlying soft biological material was removed, whilst the other lesion was not excavated. Cavities were rinsed with sterile water and dried with air. A standardised sample was taken from the mesial part of each lesion. Then, gaseous ozone (HealOzone) or 1% chlorhexidine gel (Corsodyl) was applied for 30s on both lesions of 20 children each, and a second sample was taken from the distal part of each lesion. The anaerobic microbiota was cultivated; the number of colony forming units was calculated per milligram sample. The two-sided paired t test showed no significant (P > 0.05) differences in the reduction of total bacterial counts per milligram comparing samples before and after ozone or chlorhexidine application. The tests also showed no statistically significant difference whether the superficial decayed dentine had been removed before ozone or with chlorhexidine treatment or not. It can be concluded that gaseous ozone or chlorhexidine gel application for 30s to deep occlusal carious cavities had no significant immediate antimicrobial effects whether the superficial decayed layers dentine were removed or no

Iridium complexes of the conformationally rigid IBioxMe4Ligand : hydride complexes and dehydrogenation of cyclooctene

A method for accessing the formally 14 VE iridium(III) hydride fragment {Ir(IBioxMe4)2(H)2}+ (2), containing the conformationally rigid NHC ligand IBioxMe4, is reported. Hydrogenation of trans-[Ir(IBioxMe4)2(COE)Cl] (1) in the presence of excess Na[BArF4] leads to the formation of dimeric [{Ir(IBioxMe4)2(H)2}2Cl][BArF4] (3), which is structurally fluxional in solution and acts as a reservoir of monomeric 2 in the presence of excess halogen ion abstractor. Stable dihydride complexes trans-[Ir(IBioxMe4)2(2,2′-bipyridine)(H)2][BArF4] (4) and [Ir(IBioxMe4)3(H)2][BArF4] (5) were subsequently isolated through in situ trapping of 2 using 2,2′-bipyridine and IBioxMe4, respectively, and fully characterized. Using mixtures of 3 and Na[BArF4] as a latent source of 2, the reactive monomeric fragment’s reactivity was explored with excess ethylene and cyclooctene, and trans-[Ir(IBioxMe4)2(C2H4)2][BArF4] (6) and cis-[Ir(IBioxMe4)2(COD)][BArF4] (7) were isolated, respectively, through sacrificial hydrogenation of the alkenes. Complex 6 is notable for the adoption of a very unusual orthogonal arrangement of the trans-ethylene ligands in the solid state, which has been analyzed computationally using energy and charge decomposition (EDA-NOCV). The formation of 7 via transfer dehydrogenation of COE highlights the ability to partner IBioxMe4 with reactive metal centers capable of C–H bond activation, without intramolecular activation. Reaction of 7 with CO slowly formed trans-[Ir(IBioxMe4)2(CO)2][BArF4] (8), but the equivalent reaction with bis-ethylene 6 was an order of magnitude faster, quantifying the strong coordination of COD in 7