Synthesis of Nonenolizing 2‐Acylcyclohex‐2‐enones

Cyclohexanones 2b and 2c represent the first examples of nonenolizing 2‐acylcyclohex‐2‐enones, as they bear H‐atoms neither at C(4) or C(6) of the enone ring, nor at the C‐atom vicinal to the exocyclic carbonyl group. While the CF₃CO group in 2b (and the Ac group in 2a ) are coplanar to the enone double bonds, the pivaloyl group in 2c , for steric reasons, is out of plane. Compounds 2 exhibit a pronounced sluggishness in both thermal and light‐induced bimolecular reactions.     

Synthesis and Structures of β‐Diketoiminate Complexes of Magnesium

The reaction of the β‐diketoiminate lithium complex (dipp)NacNacLi · OEt₂ ((dipp)NacNac = 2‐((2,6‐diisopropylphenyl)amino)‐4‐((2,6‐diisopropylphenyl)imino)‐pent‐2‐enyl) with iPrMgCl and MgI₂ yield the corresponding (dipp)NacNacMgiPr · OEt₂ ( 1 ) and (dipp)NacNacMgI · OEt₂ ( 2 ). The reaction of 2 with NaBH₄ in diethylether gives (dipp)NacNacMg(μ‐H)₃BH · OEt₂ ( 3 ). The core element of compounds 1 – 3 is a six‐membered ring formed by N(1)–C(1)–C(2)–C(3)–N(2) and magnesium. The structures of 1 and 2 show the β‐diketoiminate backbone in a boat‐conformation with the tetrahedrally coordinated metal center at the prow and the opposing carbon atom at the stern. The magnesium atom in 3 is octahedrally coordinated and out of the β‐diketoiminate plane.     

Tripodale Bis(2,6‐iminophosphoranyl)pyridin‐Liganden: Eisen‐ und Cobalt‐Komplexe mit Potential in der Ethen‐Polymerisation

Tripodal Bis(2,6‐iminophosphoranyl)pyridine Ligands: Iron and Cobalt Complexes with a Potential in Ethene Polymerisation By Staudinger Reaction of bis‐2,6‐diphenylphosphanyl‐pyridine with aryl‐, alkyl‐ and silylazides tripodal ligands L = 2,6‐(Ph₂P=NR)₂C₅H₃N (R = Ph 1 a , Mes 1 b , Ad  1 c , SiMe₃ 1 d ) are synthesized. The reaction of ligand 1 b  with equimolar amounts of [CoCl₂(THF)₂] and [FeCl₂(THF)_1.5] in THF does not lead to the expected neutral complexes [(k³‐L)MCl₂] but to coordination compounds of the composition L₂(CoCl₂)₃ ( 2 a ) und L(FeCl₂)₂ ( 3 ). By using acetonitrile as solvent or by crystallisation of 2 a from hot acetonitrile the cationic complex [(k³‐L)CoCl(MeCN)]Cl ( 2 b ) is formed as a second product. The molecular structure 2 b has been characterized by an X‐ray single crystal structure analysis (triclinic, P1, Z = 2, a = 1299.8(1), b = 1488.8(2), c = 1674.2(2) pm, α = 82.911(13)°, β = 76.715(12)°, γ = 72.758(11)°). A preliminary test with 3 shows, that coordination compounds of the ligand system introduced here have potential as catalysts in methyl alumoxane mediated ethene polymerisation.     

Indefinite Eigenvalue Problems with Several Singular Points and Turning Points

We consider a general class of eigenvalue problems with two-point boundary conditions on a finite interval generated by a differential equation with an indefinite weight function which has several zeros and/or poles. As a basic result we derive asymptotic estimates for a special fundamental system of solutions of the corresponding differential equation and determine the asymptotic distribution of the eigenvalues. Finally we prove the uniform convergence of eigenfunction expansions for some class of functions f.     

Struktur und Komplexbildung kleiner 1,3-dithiol-anellierter Thiakronenverbindungen

Structure and Complex Formation of Small 1,3-Dithiol Anellated Thia Crown Compounds The molecular structures of two 1,3-dithiol anellated nine membered thia crown compounds have been determined by X-ray diffraction. Their complex formation behaviour towards Ag^I and Hg^II is studied and discussed using solvent extraction experiments and molecular modeling calculations.