Elke Baum

Demetalation of Tricarbonyl(cyclopentadienone)iron Complexes Initiated by a Ligand Exchange Reaction with NaOH—X-Ray Analysis of a Complex with Nearly Square-Planar Coordinated Sodium

Asequentialexchange of one carbonyl ligand by a hydrido ligand with NaOH, and then by an iodo ligand with iodopentane and finally treatment with acid transforms tricarbonyl(η4-cyclopentadienone)iron complexes into dicarbonyl(η5-hydroxycyclopentadienyl)iodoiron complexes. These iodo complexes demetalate with high selectivity to the corresponding free ligands on contact with air in daylight. Under basic reaction conditions at the stage of the iodo complex an anionic dicarbonyl(η4-cyclopentadienone)iodoiron complex is generated, which is dimeric in the solid state and has an almost square-planar arrangement of the ligands at the sodium counterion.

Demetallierung von Tricarbonyl(cyclopentadienon)eisen-Komplexen durch eine Ligandenaustauschreaktion mit NaOH – Röntgenstrukturanalyse eines Komplexes mit nahezu quadratisch-planar koordiniertem Natrium

Durch sequentiellenAustausch eines Carbonylliganden durch einen Hydridliganden mit NaOH und einen Iodliganden mit Iodpentan und anschliesende Umsetzung mit Saure werden Tricarbonyl(η4-cyclopentadienon)eisen-Komplexe in Dicarbonyl(η5-hydroxycyclopentadienyl)iodeisen-Komplexe uberfuhrt. Diese demetallieren beim Kontakt mit Luft an Tageslicht hochselektiv zu den entsprechenden freien Liganden. Unter basischen Bedingungen reagiert der Iodkomplex zu einem anionischen Dicarbonyl(η4-cyclopentadienon)iodeisen-Komplex, der im Festkorper dimer vorliegt und dessen Natrium-Gegenion nahezu quadratisch-planar koordiniert wird.

Transition Metal-Diene Complexes in Organic Synthesis, Part 25.1 Cycloadditions of Annulated 2,5-Bis(trimethylsilyl)cyclopentadienones

Abstract The Diels-Alder reaction of 3.4-annulated 2,5-bis(trimethylsilyl)cyclopentadienones provided stereoselectively the endo products. Consecutive [4+2] and photochemical [2+2] cycloaddition with p -benzoquinone afforded the hexacyclic cage compound 11 .

A new synthetic entry to phosphinophosphinidene complexes. Synthesis and structural characterisation of the first side-on bonded and the first terminally bonded phosphinophosphinidene zirconium complexes [μ-(1,2∶2-η-tBu2PP){Zr(Cl)Cp2}2] and [{Zr(PPhMe2)Cp2}(η1-P–PtBu2)]

The reactions of lithiated diphosphanes with transition metal chlorides constitute a new general entry to phosphinophosphinidene complexes: the reaction of Cp2ZrCl2(Cp = C5H5) with tBu2P-P(SiMe3)Li (molar ratio approximately 1:1) yields [mu-(1,2:2-eta-tBu2P=P)[Zr(Cl)Cp2]2]; the reaction of Cp2ZrCl2 with tBu2P-P(SiMe3)Li (molar ratio approximately 1:2) and an excess of PPhMe2 in DME yields the first terminally bonded phosphinophosphinidene complex, [[Zr(PPhMe2)Cp2](eta1-P-PtBu2)].

Transition metal complexes in organic synthesis. Part 58: First enantioselective total synthesis of the potent neuronal cell protecting substance carquinostatin A from (R)-propene oxide

Abstract Starting from enantiopure (R)-propene oxide the first enantioselective total synthesis of the potent neuronal cell protecting alkaloid carquinostatin A has been accomplished by using iron- and nickel-mediated coupling reactions.

Transition metal-diene complexes in organic synthesis, part 23. Total synthesis of the marine alkaloid hyellazole☆

Abstract The marine alkaloid hyellazole has been synthesized in a convergent manner from the tricarbonyliron-complexed cyclohexadienylium cation and a fully functionalized arylamine by an electrophilic aromatic substitution and subsequent oxidative cyclization.

Ditrielanes (R3Si)2E−E(SiR3)2 and Heterocubanes (R3Si)4E4Y4 (R3Si = tBu3Si, tBu2PhSi; E = Al, Ga, In, Tl; Y = O, Se)

Ditrielanes R*2E−ER*2 (R* = SitBu3; E = Al, In, Tl), R′2E−ER′2 (R′ = SitBu2Ph; E = In, Tl) and R*2Ga−GaR*(SiMe3) are prepared in alkanes (i) from ECl3 (E = Al, In, Tl) and NaR* via isolable R*2ECl (reaction of GaCl3 and NaR* leads to R*2GaGaR* instead of R*2Ga−GaR*2), (ii) from EBr (E = In, Tl) and NaR* or NaR′ (reaction of AlBr or GaBr and NaR* leads to R*4Al4 or R*8Ga18 and R*8Ga22), (iii) from NaGa2R*3 and Me3SiCl. According to X-ray structure analyses, the ditrielanes contain two planar groups R2EE which are orthogonal to each other (R = R*; angle REER ca. 90°) or nearly orthogonal (R = R′; angle REER ca. 80°). All compounds are deeply colored. The λmax value of the visible absorption shifts with increasing atomic number of E and with the increasing angle between the R2EE planes to longer wavelengths (ruby R*4Al2, deep-violet R*4In2, dark-green R*4Tl2; red-violet R′4In2, dark-blue R′4Tl2). Thermolysis of R*4E2 in alkanes at about 100 °C leads to R*3Al2·/R*4Al3·/R*4Al4, to R*3Ga2·/R*4Ga4, to (R*4In6)/R*8In12 and to Tl, respectively. R′4E2 thermolizes under formation of an In or Tl mirror. The ditrielanes R*4E2 are stable against R*2ECl (reaction of GaCl3 and NaR* leads to R*2GaGaR* and E−E bond cleavage with the formation of R*EBr2 (e.g. R*InBr2) besides R*H and H2. Air transforms the ditrielanes into R*OH or R′OH. On the other hand, halogens oxidize R*4E2 under formation of R*2EHal (e.g. R*2AlI), R*EHal2 (e.g. R*InBr2) or thermolysis products of the dihalides (e.g. R*Br/TlBr). Selenium gives with R*4E2 heterocubanes R*4E4Se4 (E = Al, In, Tl). Analogous heterocubanes R*4E4O4 (E = Al, Ga) are synthesized from tetrahedranes R*4E4 and oxygen. X-ray structure analyses for R*4In4Se4, R*4Al4O4 − besides the mentioned ditrielanes − are presented.

[Ga18(SitBu3)8] and [Ga22(SitBu3)8]—Syntheses and Structural Characterization of Novel Gallium Cluster Compounds

The novel neutral gallium cluster compounds [Ga18R*8] (1) and [Ga22R*8] (2) are obtained by warming up a metastable solution of gallium(I) bromide in THF/C6H5CH3 after addition of equimolar amounts of supersilyl sodium NaR* from -78 degrees C to room temperature (R* = SitBu3 = supersilyl). From X-ray structure analyses, the observed arrangements of the 18 and 22 Ga atoms in 1 and 2, respectively, are comparable with an 18 atom section of the beta-Ga modification, or show at least some kind of relationship to a 22 atom section of the Ga-III modification. This allows a description of both the clusters as metalloid. The topology of the atoms in 2 is also well explained by the Wade-Mingos rules as an eightfold capped closo-Ga14 cluster, whereby the Ga atoms of Ga14 occupy the center and the corners of a cuboctahedron with one Ga3 face replaced by a Ga4 face. Some concepts are presented about the formation mechanism, the cluster growth, and the metalloid character of the two Ga cluster compounds.

TRANSITION METAL COMPLEXES IN ORGANIC SYNTHESIS, PART 53. IRON-MEDIATED SYNTHESIS OF HYELLAZOLE AND ISOHYELLAZOLE

Abstract The synthesis of the marine alkaloid hyellazole and the non-natural regioisomer isohyellazole is reported starting from the tricarbonyliron-complexed cyclohexadienylium cation and the fully functionalized arylamines by electrophilic aromatic substitution and oxidative cyclization.

Cycloadditions of Allylsilanes, Part 13 - Lewis Acid-Promoted Stereospecific [2+2] Cycloaddition of Crotylsilanes and Methyl Propynoate

Abstract The titanium tetrachloride-promoted reaction of the ( Z )- and ( E )-crotylsilanes 6 and 9 with methyl propynoate ( 1 ) provides by stereospecific [2+2] cycloaddition the cis - and trans -3,4-disubstituted cyclobutenes 7 and 10 .