Osmium-Centered Oxetylidene: Formation and Cleavage
摘要:
The first transition-metal oxetylidene complex has been prepared by reaction of OsCl(eta(5)-C5H5)(CO)((PPr3)-Pr-i) with 3,3-di(methoxycarbonyl)-5-hexyn-1-al and AgBF4. This novel compound is transformed into a hydroxyalkenylcarbene isomer by deprotonation and subsequent protonation of the resulting alpha,beta-unsaturated acyl transient species. In fluorobenzene at 90 degrees C, the four-membered ring undergoes cycloreversion to afford a cis-dicarbonyl derivative and the cycloalkene.
New Cyclopentadienylosmium Derivatives Prepared from the Five-Coordinate Complex [OsHCl(CO)(PPri3)2]
摘要:
The reaction of [OsHCl(CO)(PPr3i)(2)] (1) with cyclopentadiene in refluxing methanol affords the novel cyclopentadienylosmium(II) complex [OsH(eta(5)-C5H5)(CO)-(PPr3i)] (2). Reaction of 2 with CCl4 in pentane gives the chloro complex [Os(eta(5)-C5H5)Cl(CO)(PPr3i)] (3). The protonation of 2 with HBF4.Et(2)O leads to the transdihydridoosmium(IV) complex[OsH2(eta(5)-C(5)H5)(CO)(PPr3i)]-BF (4). Treatment of the chloro complex 3 with AgBF4 followed by the terminal alkyne phenylacetylene or 1-ethynhyl-1-cyclohexanol gives the stable vinylidene [Os-(eta(5)-C5H5){=C=C(H)Ph}(CO)(PPr3i)]BF4 (5) or vinylvinylidene [Os(eta(5)-C5H5){=C=C(H)C=CH(CH2)(3)CH2}(CO)-(PPr3i)]BF4 (6), respectively.