[(η(5)-C5Me5)Ru](+) fragments ligated to polyaromatic hydrocarbons: an experimental and computational approach to pathways for haptotropic migration.

Ligand exchange reactions between [Cp*Ru(NCMe)3][PF6], where Cp* represents η(5)-C5Me5, and the polycyclic aromatic hydrocarbons (PAHs) pyrene, acenaphthylene and fluoranthene afforded the known [Cp*Ru(η(6)-pyrene)][PF6] (1) and the new mixed sandwiches [Cp*Ru(η(6)-acenaphthylene)][PF6] (2) and [Cp*Ru(η(6)-fluoranthene)][PF6] (3), respectively, isolated in quantitative yields (94-100%). Complex 3 is formed as a mixture of two isomers: 3A as the major product where the [Cp*Ru(+)] moiety is coordinated to the naphthalene fragment of fluoranthene, and 3B with the coordination of the arenophile to the peripheral benzene ring, in a 90/10 spectroscopic ratio. The composition and identity of the complexes were deduced by elemental analysis, (1)H and (13)C multidimensional NMR spectroscopy, and mass spectrometry.

Stable divalent germanium, tin and lead amino(ether)-phenolate monomeric complexes: structural features, inclusion heterobimetallic complexes, and ROP catalysis.

Stable germanium(II) and lead(II) amido complexes {LO(i)}M(N(SiMe3)2) (M = Ge(II), Pb(II)) bearing amino(ether)phenolate ligands are readily available using the proteo-ligands {LO(i)}H of general formula 2-CH2NR2-4,6-tBu2-C6H2OH (i = 1, NR2 = N((CH2)2OCH3)2; i = 2, NR2 = NEt2; i = 3, NR2 = aza-15-crown-5) and M(N(SiMe3)2)2 precursors. The molecular structures of these germylenes and plumbylenes, as well as those of {LO(3)}GeCl, {LO(3)}SnCl and of the congeneric {LO(4)}Sn(II)(N(SiMe3)2) where NR2 = aza-12-crown-4, have been determined crystallographically. All complexes are monomeric, with 3-coordinate metal centres.

Heteroleptic tin(II) initiators for the ring-opening (co)polymerization of lactide and trimethylene carbonate: mechanistic insights from experiments and computations.

The tin(II) complexes {LO(x)}Sn(X) ({LO(x)}(-) =aminophenolate ancillary) containing amido (1-4), chloro (5), or lactyl (6) coligands (X) promote the ring-opening polymerization (ROP) of cyclic esters. Complex 6, which models the first insertion of L-lactide, initiates the living ROP of L-LA on its own, but the amido derivatives 1-4 require the addition of alcohol to do so. Upon addition of one to ten equivalents of iPrOH, precatalysts 1-4 promote the ROP of trimethylene carbonate (TMC); yet, hardly any activity is observed if tert-butyl (R)-lactate is used instead of iPrOH.

Lobarin from the Sumatran lichen, Stereocaulon halei.

The diphenyl ether, lobarin (1) (syn. lobariol carboxylic acid) related to lobaric acid was isolated for the first time as a natural product along with five known compounds from Stereocaulon halei, a fruticose lichen collected in Indonesia. The structure of lobarin was elucidated by spectroscopic data analysis and its most stable conformers were determined by molecular mechanic dynamic calculations.

Synthetic and mechanistic aspects of the immortal ring-opening polymerization of lactide and trimethylene carbonate with new homo- and heteroleptic tin(II)-phenolate catalysts.

Several new heteroleptic Sn(II) complexes supported by amino-ether phenolate ligands [Sn{LO(n)}(Nu)] (LO(1)=2-[(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)methyl]-4,6-di-tert-butylphenolate, Nu=NMe(2) (1), N(SiMe(3))(2) (3), OSiPh(3) (6); LO(2)=2,4-di-tert-butyl-6-(morpholinomethyl)phenolate, Nu=N(SiMe(3))(2) (7), OSiPh(3) (8)) and the homoleptic Sn{LO(1)}(2) (2) have been synthesized. The alkoxy derivatives [Sn{LO(1)}(OR)] (OR=OiPr (4), (S)-OCH(CH(3))CO(2)iPr (5)), which were generated by alcoholysis of the parent amido precursor, were stable in solution but could not be isolated. [Sn{LO(1)}](+)[H(2)N{B(C(6)F(5))(3)}(2)](-) (9), a rare well-defined, solvent-free tin cation, was prepared in high yield.

Electrochemical synthesis and chemistry of chiral 1-cyanotetrahydroisoquinolines. An approach to the asymmetric syntheses of the alkaloid (-)-crispine a and its natural (+)-antipode.

The stereoselective convergent total syntheses of both enantiomers of the tetrahydroisoquinoline (THIQ) alkaloid crispine A are described. The THIQ precursors (-)-6 (90:10 dr) and (-)-11 (85:15 dr) were prepared from the alkylation-reduction sequence of a common α-amino nitrile (+)-4 derivative that has been conveniently prepared by anodic cyanation. Elaboration of the pyrrolidine ring of the title compound was cleanly achieved by two efficient ring closures methods involving (a) the displacement of a halogen atom and (b) the formation of a cyclic iminium cation to afford (-)-crispine A in 90% and 85% yields, respectively.

Topological dependence of the magnetic exchange coupling in arylethynyl-bridged organometallic diradicals containing [(eta(2)-dppe)(eta(5)-C(5)Me(5))Fe(III)](+) fragments.

We have investigated the spin distribution and determined the magnetic exchange coupling J(ab) (defined according to the following Hamiltonian: H(spin) = -2J(ab)S(a).S(b)) for three arylethynyl-bridged organoiron(III) diradicals containing [(eta(2)-dppe)(eta(5)-C(5)Me(5))Fe(III)](+) fragments. Considering the distance separating the Fe(III) centers (>or=11 A), remarkably large intramolecular magnetic interactions between unpaired spins were found for two of them.

Selective Activation of Ar-Cl and Ar-C Bonds with Iron(II) Complexes.

The electrophilic iron-carbene chelate complexes 1 and 2 react with alkoxides RO to give the neutral chelate complex 3 and the carbene complex 4, respectively. Depending on the nature of the chelating ortho substituent, selective activation of the Ar-Cl or Ar-C bond occurs; these processes are promoted by the chelation.