Osmium Models of Intermediates Involved in Catalytic Reactions of Alkylidenecyclopropanes

The complex [OsCp­{κ³-<i>P</i>,<i>C</i>,<i>C</i>-PⁱPr₂[C­(CH₃)CH₂]}­(CH₃CN)]­PF₆ (<b>1</b>) reacts with (2-pyridyl)­methylenecyclopropane, at room temperature, to give initially the cyclobutylidene derivative [Os­(η⁵-C₅H₅)­(CCH₂CH₂CH-<i>o</i>-C₅H₄N)­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>2</b>), as a result of the ring expansion of the alkylidenecyclopropane unit. Over time complex <b>2</b> rearranges into the cyclobutene derivative [Os­(η⁵-C₅H₅)­{η²-C­(CHCH₂CH₂)-<i>o</i>-C₅H₄N}­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>3</b>). The reaction of <b>1</b> with (2-pyridyl)­methylenecyclopropane at room temperature also affords the phosphinomethanide metallacycle [Os­(η⁵-C₅H₅)­{κ⁴-<i>P</i>,<i>C</i>^a,<i>C</i>^b,<i>N</i>-PⁱPr₂[C^a(Me)­CH₂CH)­(C^bCH₂CH₂-<i>o</i>-C₅H₄N]}]­PF₆ (<b>4</b>) as a minor product, which becomes the major product of the reaction at 45 °C. This osmacyclopentane results from the C–C coupling of the isopropenyl substituent of the phosphine ligand and the organic substrate. In acetone at 75 °C, the reaction of <b>1</b> with (2-pyridyl)­methylenecyclopropane leads to the 2-alkylidene-1-osmacyclobutane [Os­(η⁵-C₅H₅)­{κ³-<i>N</i>,<i>C</i>^a,<i>C</i>^b-C^a(CH₂C^bH₂)­(CH-<i>o</i>-C₅H₄N)}­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>5</b>), as a consequence of the oxidative addition of one of the C­(sp²)–C­(sp³) bonds of the cyclopropane unit of the substrate to the osmium atom, along with <b>6</b>, a diastereomer of <b>4</b>. Complexes <b>3</b>–<b>5</b> have been characterized by X-ray diffraction analysis. DFT calculations suggest that all of the reaction products are derived from a common key 1-osma-2-azacyclopent-3-ene intermediate (<b>D</b>)

Osmium Models of Intermediates Involved in Catalytic Reactions of Alkylidenecyclopropanes

The complex [OsCp­{κ³-<i>P</i>,<i>C</i>,<i>C</i>-PⁱPr₂[C­(CH₃)CH₂]}­(CH₃CN)]­PF₆ (<b>1</b>) reacts with (2-pyridyl)­methylenecyclopropane, at room temperature, to give initially the cyclobutylidene derivative [Os­(η⁵-C₅H₅)­(CCH₂CH₂CH-<i>o</i>-C₅H₄N)­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>2</b>), as a result of the ring expansion of the alkylidenecyclopropane unit. Over time complex <b>2</b> rearranges into the cyclobutene derivative [Os­(η⁵-C₅H₅)­{η²-C­(CHCH₂CH₂)-<i>o</i>-C₅H₄N}­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>3</b>). The reaction of <b>1</b> with (2-pyridyl)­methylenecyclopropane at room temperature also affords the phosphinomethanide metallacycle [Os­(η⁵-C₅H₅)­{κ⁴-<i>P</i>,<i>C</i>^a,<i>C</i>^b,<i>N</i>-PⁱPr₂[C^a(Me)­CH₂CH)­(C^bCH₂CH₂-<i>o</i>-C₅H₄N]}]­PF₆ (<b>4</b>) as a minor product, which becomes the major product of the reaction at 45 °C. This osmacyclopentane results from the C–C coupling of the isopropenyl substituent of the phosphine ligand and the organic substrate. In acetone at 75 °C, the reaction of <b>1</b> with (2-pyridyl)­methylenecyclopropane leads to the 2-alkylidene-1-osmacyclobutane [Os­(η⁵-C₅H₅)­{κ³-<i>N</i>,<i>C</i>^a,<i>C</i>^b-C^a(CH₂C^bH₂)­(CH-<i>o</i>-C₅H₄N)}­{PⁱPr₂[C­(Me)CH₂]}]­PF₆ (<b>5</b>), as a consequence of the oxidative addition of one of the C­(sp²)–C­(sp³) bonds of the cyclopropane unit of the substrate to the osmium atom, along with <b>6</b>, a diastereomer of <b>4</b>. Complexes <b>3</b>–<b>5</b> have been characterized by X-ray diffraction analysis. DFT calculations suggest that all of the reaction products are derived from a common key 1-osma-2-azacyclopent-3-ene intermediate (<b>D</b>)

Enterotoxigenic Potential of Staphylococcus intermedius

Staphylococcal food poisoning (SFP) caused by enterotoxigenic staphylococci is one of the main food-borne diseases. In contrast to Staphylococcus aureus, a systematic screening for the enterotoxins has not yet been performed on the genomic level for the coagulase-positive species S. intermedius. Therefore, the enterotoxigenic potential of 281 different veterinary (canine, n = 247; equine, n = 23; feline, n = 9; other, n = 2) and 11 human isolates of S. intermedius was tested by using a multiplex PCR DNA-enzyme immunoassay system targeting the staphylococcal enterotoxin genes sea, seb, sec, sed, and see. Molecular results were compared by in vitro testing of enterotoxin production by two immunoassays. A total of 33 (11.3%) S. intermedius isolates, including 31 (12.6%) canine isolates, 1 equine isolate, and 1 human isolate, tested positive for the sec gene. In vitro production of the respective enterotoxins was detected in 30 (90.9%) of these isolates by using immunological tests. In contrast, none of 65 veterinary specimen-derived isolates additionally tested and comprising 13 (sub)species of coagulase-negative staphylococci were found to be enterotoxigenic. This study shows on both molecular and immunological levels that a substantial number of S. intermedius isolates harbor the potential for enterotoxin production. Since evidence for noninvasive zoonotic transmission of S. intermedius from animal hosts to humans has been documented, an enterotoxigenic role of this microorganism in SFP via contamination of food products may be assumed