Helvetica Chimica Acta

doi: 10.1002/hlca.19840670101pmid: N/A

Ortiz, J. V.; Havlas, Zdenêk; Hoffmann, Roald

doi: 10.1002/hlca.19840670102pmid: N/A

This work considers the theoretical aspects of the shift of an alkyl(or aryl) group from a coordinated phosphine to the 16‐electron d8 transition metal to which it is coordinated. This rearrangement at first seems to resemble an anionic [1,2]‐sigmatropic shift. But a detailed analysis of the relatively low barrier calculated for the reaction shows how all traces of the forbiddeness of the reaction have vanished. Phenyl migration should eb still more facile. We also analyze in some detail the possible pathways of alkyl halide addition to a phenyl‐Pt complex. An alkyl migration, now from metal to coordinated C‐atom, could possibly intervene in this process.

Hakimelahi, Gholam Hosein; Khalafi‐Nezhad, Ali

doi: 10.1002/hlca.19840670103pmid: N/A

A new route to the synthesis of the title compound is described.

Kramer, Andreas; Pfander, Hanspeter

doi: 10.1002/hlca.19840670104pmid: N/A

C45‐ and C50‐Carotenoids. Synthesis of Optically Active Acyclic C15‐End Groups

Siegfried, Liselotte; Kaden, Thomas A.

doi: 10.1002/hlca.19840670105pmid: N/A

A series of 12‐, 14‐, and 16‐membered N2S2‐macrocycles (9–11 and 19–21) with cis and trans‐arrangement of the heteroatoms have been synthesized by high‐dilution cyclization and subsequent reduction of the amides with B2H6. With these ligands the corresponding Cu2+‐complexes were prepared and their UV/VIS spectra, their electrochemistry and their EPR properties have been studied. Generally three absorption bands at 270–320 nm, 330–370 nm and 530–620 nm can be observed in aqueous solution and these have been assigned to the N→Cu2+ and S→Cu2+ charge‐transfer bands and to the d‐d* transition, respectively. The cyclic voltammetry in CH3CN shows in all cases a reversible or quasi‐reversible Cu2+/Cu+‐transition at potentials of 10–480 mV against SHE. The values of g‖ and A‖ obtained from EPR spectra indicate that the geometry of the Cu2+‐complex of the 14‐membered cis‐N2S2‐macrocycle is less distorted than that of the other complexes.

Wallis, John D.; Dunitz, Jack D.

doi: 10.1002/hlca.19840670106pmid: N/A

In the crystal structure of the title compound at 98 K the dimethylamino group has pyramidal geometry. The nitrogenlone pair is not directed towards the triple bond; instead, one NCH3 bond lies almost in the plane of the disubstituted ring, directed away from the triple bond, while the other NCH3 bond and the lone pair are directed to opposite sides of the plane, nearer to the acetylene. There is a remarkably short intramolecular contact (2.39 Å) between a methyl H‐ and an acetylenic C‐atom. The Taft σI parameter of the arylethynyl substituent appears to be similar to that of a carboxylic ester, judging from the bond‐angle deformation at the ipso‐C‐atom.

Heilbronner, Edgar; Wirz, Jakob; Soulen, Robert L.

doi: 10.1002/hlca.19840670107pmid: N/A

The He(Iα) photoelectron (PE) spectra of tris(perfluorocyclobuta)benzene 4(F) 3,3,4,4,7,7,8,8,11,11,12,12‐Dodecafluorotetracyclo[8.2.0.02,5.06,9]dodeca‐1,5,9‐triene , tris(perfluorocyclopenta)benzene 5(F) 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9‐Octadecafluoro‐2,3,4,5,6,7,8,9‐octahydro‐1H‐trindene. , tetrakis(perfluorocyclobuta)cyclooctatetraene 6(F) 3,3,4,4,7,7,8,8,11,1l,l2,l2,l5,15,16,16‐Hexadecafluoropentacyclo[12.2.0.02,5.06,9.010,13]hexadeca‐1,5,9,13‐tetraene. , and of tetrakis(perfluorocyclopenta)cyclooctatetraene 7(F) 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12‐Tetracosafluoro‐1,2,3,4,5,6,7,8,9,10,11,12‐dodeca‐hydrotetracyclopenta[a,c,e,g]cyclooctene. are reported. A tentative assignment of the PE spectra is derived by empirical correlation with those of relevant reference compounds. The results suggest that 6(F) retains the D4h‐conformation in the gas phase, i.e. A conformation with a planar cyclooctatetraene ring, as observed in the crystal. All four compounds exhibit a sharp increase of their first ionization energies, relative to the corresponding parent hydrocarbons, due to the perfluoro effect.

Wagner, Hildebert; Habermeier, Helmut; Schulten, Hans‐Rolf

doi: 10.1002/hlca.19840670108pmid: N/A

The Heart Glycosides of the Arrow Poison of Lophopetalum toxicum LOHER

Boron‐Rettore, Patrizia; Grove, David M.; Venazi, Luigi M.

doi: 10.1002/hlca.19840670109pmid: N/A

The ligand 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene (1) has been used to prepare complexes of the type [PtL(1)] (L  C2H4, CH2CHCO2Me, PhCCPh, MeCCMe, MeO2CCCCO2Me, (i‐Pr)O2CCCCO2(i‐Pr), Ph3P and CO). It is shown that these complexes are less labile than the corresponding species [PtL(Ph3P)2]. The preparation of complexes trans‐[PtX(R)(1)] by oxidative addition of RX (RX  PhCH2Br and Mel) to [Pt(C2H4)(1)] is described. The isolation of [PtO2(CH3)2CO(1)] is also reported.

Karpf, Martin

doi: 10.1002/hlca.19840670110pmid: N/A

The Acylation of Acetylenes with β,γ‐Unsaturated Acid Chlorides, A New Synthesis of 5‐Substituted 2‐Cyclopentenones