Rare Earth and Main Group Metal Poly(hydrosilyl) Compounds

The potassium poly­(hydrosilyl) compound KSi­(SiHMe₂)₃, which contains three β-SiH groups, is synthesized by the reaction of Si­(SiHMe₂)₄ and KO<i>t</i>Bu. A single-crystal X-ray diffraction study reveals chains composed of head-to-tail KSi­(SiHMe₂)₃ monomers. This potassium poly­(hydrosilyl) anion reacts with divalent metal halide salts in THF to form the bis­(silyl) compounds Mg­{Si­(SiHMe₂)₃}₂THF₂ (<b>1·THF</b>_<b>2</b>), Ca­{Si­(SiHMe₂)₃}₂THF₃ (<b>2·THF</b>_<b>3</b>), and Yb­{Si­(SiHMe₂)₃}₂THF₃ (<b>3·THF</b>_<b>3</b>). A trivalent yttrium bis­(silyl), as part of a KCl-containing polymeric chain, is supported by K↼H–Si bridging interactions. The N donors pyridine (<b>py</b>) and dimethylaminopyridine (<b>DMAP</b>) readily substitute THF, giving tetrahedral magnesium and octahedral calcium silyl compounds. The one-bond silicon–hydrogen coupling constants (¹<i>J</i>_SiH), infrared stretching frequencies (ν_SiH), and solid-state structures of <b>2·py</b>_<b>4</b> and <b>3·THF</b>_<b>3</b> indicate classical two center-two electron bonding between the metal center and the silyl ligand, as well as terminal (nonbridging) Si–H bonds within the silyl ligands. The magnesium and calcium compounds readily react with the Lewis acids PhB­(C₆F₅)₂ and B­(C₆F₅)₃ to give hydridoborate salts, whereas {κ³-To^M}₂Yb (<b>5</b>) (To^M = tris­(4,4-dimethyl-2-oxazolinyl)­phenyl borate) is formed by reaction of TlTo^M and <b>3·THF</b>_<b>3</b>

Cyclopentadienyl-bis(oxazoline) Magnesium and Zirconium Complexes in Aminoalkene Hydroaminations

A new class of cyclopentadiene-bis­(oxazoline) compounds and their piano-stool-type organometallic complexes have been prepared as catalysts for hydroamination of aminoalkenes. The two compounds MeC­(Ox^Me2)₂C₅H₅ (Bo^MCpH; Ox^Me2 = 4,4-dimethyl-2-oxazoline) and MeC­(Ox^Me2)₂C₅Me₄H (Bo^MCp^tetH) are synthesized from C₅R₄HI (R = H, Me) and MeC­(Ox^Me2)₂Li. These cyclopentadiene-bis­(oxazolines) are converted into ligands that support a variety of metal centers in piano-stool-type geometries, and here we report the preparation of Mg, Tl, Ti, and Zr compounds. Bo^MCpH and Bo^MCp^tetH react with MgMe₂(O₂C₄H₈)₂ to give the magnesium methyl complexes {Bo^MCp}­MgMe and {Bo^MCp^tet}­MgMe. Bo^MCpH and Bo^MCp^tetH are converted to Bo^MCpTl and Bo^MCp^tetTl by reaction with TlOEt. The thallium derivatives react with TiCl₃(THF)₃ to provide [{Bo^MCp}­TiCl­(μ-Cl)]₂ and [{Bo^MCp^tet}­TiCl­(μ-Cl)]₂, the former of which is crystallographically characterized as a dimeric species. Bo^MCpH and Zr­(NMe₂)₄ react to eliminate dimethylamine and afford {Bo^MCp}­Zr­(NMe₂)₃, which is crystallographically characterized as a monomeric four-legged piano-stool compound. {Bo^MCp}­Zr­(NMe₂)₃, {Bo^MCp}­MgMe, and {Bo^MCp^tet}­MgMe are efficient catalysts for the hydroamination/cyclization of aminoalkenes under mild conditions

Host factors are associated with vaginal microbiome structure in pregnancy in the ECHO Cohort Consortium

Using pooled vaginal microbiota data from pregnancy cohorts (N = 683 participants) in the Environmental influences on Child Health Outcomes (ECHO) Program, we analyzed 16S rRNA gene amplicon sequences to identify clinical and demographic host factors that associate with vaginal microbiota structure in pregnancy both within and across diverse cohorts. Using PERMANOVA models, we assessed factors associated with vaginal community structure in pregnancy, examined whether host factors were conserved across populations, and tested the independent and combined effects of host factors on vaginal community state types (CSTs) using multinomial logistic regression models. Demographic and social factors explained a larger amount of variation in the vaginal microbiome in pregnancy than clinical factors. After adjustment, lower education, rather than self-identified race, remained a robust predictor of L. iners dominant (CST III) and diverse (CST IV) (OR = 8.44, 95% CI = 4.06–17.6 and OR = 4.18, 95% CI = 1.88–9.26, respectively). In random forest models, we identified specific taxonomic features of host factors, particularly urogenital pathogens associated with pregnancy complications (Aerococcus christensenii and Gardnerella spp.) among other facultative anaerobes and key markers of community instability (L. iners). Sociodemographic factors were robustly associated with vaginal microbiota structure in pregnancy and should be considered as sources of variation in human microbiome studies