Calcium Complexes Having Different Amidinate Ligands - Synthesis and Structural Diversity

A one-pot reaction of α-diimine ligand 1,4-disubstituted diazabutadienes (DAD) with potassium benzyl and anhydrous calcium iodide in 1:1:1 molar ratio afforded unprecedented 3-phenylprop-2-ene-di-amido calcium compound [κ2-(THF)4Ca{DippNC(=CHPh)CH2NDipp}] (1) (Dipp = 2,6-diisopropylphenyl) in good yield. The solid-state structure of the compound 1 revealed the formation of dianionic 3-phenylprop-2-ene-di-amido ligand having an exocyclic olefinic bond derived from neutral α-diimine fragment. However, analogous reactions with three different carbodiimides (RN=C=NR; R=Cy, iPr and tBu) with alkyl potassium and anhydrous calcium diiodide yielded corresponding homoleptic calcium compounds with amidinato ligand [κ2-(THF)2Ca{RN=C(CH2Ph)NR}2] [R=Cy (2), iPr (3) and tBu (4)]. A separate reaction of DAD ligand, LiCH2SiMe3 and anhydrous ZnCl2 in diethylether solvent produced tri-coordinated zinc compound [κ2- {DippN=C(CH2SiMe3)CH2NDipp}Zn[κ1-{DippN=C(CH2SiMe3)CH2N-Dipp}] (5) having amidinato moieties in the zinc coordination sphere in high yield. Molecular structures of compounds 2–5 in their solid states were also established

Intestinal carriage of Staphylococcus aureus: How does its frequency compare with that of nasal carriage and what is its clinical impact?

The bacterial species Staphylococcus aureus, including its methicillin-resistant variant (MRSA), finds its primary ecological niche in the human nose, but is also able to colonize the intestines and the perineal region. Intestinal carriage has not been widely investigated despite its potential clinical impact. This review summarizes literature on the topic and sketches the current state of affairs from a microbiological and infectious diseases' perspective. Major findings are that the average reported detection rate of intestinal carriage in healthy individuals and patients is 20% for S. aureus and 9% for MRSA, which is approximately half of that for nasal carriage. Nasal carriage seems to predispose to intestinal carriage, but sole intestinal carriage occurs relatively frequently and is observed in 1 out of 3 intestinal carriers, which provides a rationale to include intestinal screening for surveillance or in outbreak settings. Colonization of the intestinal tract with S. aureus at a young age occurs at a high frequency and may affect the host's immune system. The frequency of intestinal carriage is generally underestimated and may significantly contribute to bacterial dissemination and subsequent risk of infections. Whether intestinal rather than nasal S. aureus carriage is a primary predictor for infections is still ill-defined

Aluminum Alkyls Containing Guanidinate Ligands

The synthesis and structures of new aluminum complexes incorporating guanidinate ligands (R2NC(NR')2-) are described. The reaction of iPrN=C=NiPr with LiNR2 reagents yields Li[R2NC(NiPr)2] guanidinate salts, which are reacted in situ with AlCl3 or AlMe2Cl to afford {R2NC(NiPr)2}AlCl2 (1a, R = Me; 1b, R = Et; 1c, R = iPr; 1d, R = SiMe3) or {R2NC(NiPr)2}AlMe2 (2a, R = Me; 2b, R = Et; 2c, R = iPr), respectively. The reaction of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) with AlMe3 generates {(-hpp)AlMe2}2 (3). Complexes 1a, 1d, and 3 have been characterized by X-ray crystallography. 1a and 1d adopt monomeric structures with symmetric chelated bidentate guanidinate ligands. Delocalization of the -NR2 lone pair into the chelate ring is important for 1a but not for 1d, due to N-Si -bonding and steric crowding. The bicyclic structure of the hpp- ligand enforces a dimeric -hpp- structure for 3