Über die Reaktion von Propiolsäure und Propiolsäureester mit Cyclohexanon

In the presence of potassium t-butoxide or potassium hydroxide, propiolic acid adds two molecules of cyclohexanone to form the isomeric seq-cis- and seq-trans-7, 14-Dioxa-dispiro[5.1.5.2]pentadec-15-yliden-acetic acids IIa and IIIa, respectively. Methyl propiolate and cyclohexanone react analogously in the presence of potassium t-butoxide, yielding the corresponding esters. The structure of these condensation products follows from their physical properties and from degradation reactions to known compounds.     

Synthese,Struktur und Reaktionen von Vanadiumsäureestern VO(OR)3: Umesterung und Reaktion mit Oxalsäure

Synthesis, Structure, and Reactions of Vanadium Acid Esters VO(OR)₃: Transesterification and Reaction with Oxalic Acid The reaction of tert.‐Butyl Vanadate VO(O‐tert.Bu)₃ ( 1 ) with H₂C₂O₄ in the primary alcohols ethanol and propanol results in the formation of (ROH)(RO)₂OV^V(C₂O₄)V^VO(OR)₂(HOR) (with R = C₂H₅ 2 and R = C₃H₇ 3 ). Compounds 2 and 3 are the first structurally characterized neutral, binuclear oxo‐oxalato‐complexes with pentavalent vanadium. The two vanadium atoms are connected by a bisbidentate oxalate group. The {VO₆} coordination at each vanadium site is completed by a terminal oxo group, an alcohol ligand and two alcoxide groups. The binuclear molecules are connected to chains by hydrogen bonding. In the case of 2 a reversible isomorphic phase transition in the temperature range of –90 °C to –130 °C is observed. From methanolic solution the polymeric Methyl Vanadate [VO(OMe)₃] ( 4 ) was obtained by transesterification. A report on the crystal structures of 1 , 2 and 3 as well as a redetermination of the structure of 4 is given. Crystal data: 1, orthorhombic, Cmc2₁, a = 16.61(2) Å, b = 9.274(6) Å, c = 10.784(7) Å, V = 1662(2) ų, Z = 4, d_c = 1.144 gcm^–1; 2 (–90 ° C) , monoclinic, I2/a, a = 33.502(4) Å, b = 7.193(1) Å, c = 15.903(2) Å und β = 143.060(3)°, V = 2303(1) ų, Z = 4, d_c = 1.425 gcm^–1; 2 (–130 ° C) , monoclinic, I2/a, a = 33.274(4) Å, b = 7.161(1) Å, c = 47.554(5) Å, β = 142.798(2)°, V = 6851(1) ų, Z = 12, d_c = 1.438 gcm^–1; 3 , triklinic, P1, a = 9.017(5) Å, b = 9.754(5) Å, c = 16.359(9) Å, α = 94.87(2)°, β = 93.34(2)°, γ = 90.42(2)°, V = 1431(1) ų, Z = 2, d_c = 1.340 gcm^–1; 4 , triklinic, P1, a = 8.443(2) Å, b = 8.545(2) Å, c = 9.665(2) Å, α = 103.202(5)°, β = 96.476(5)°, γ = 112.730(4)°, V = 610.2(2)ų, Z = 4, d_c = 1.742 gcm^–1.     

Schwermetallchelate von α-Cyano-β-amino-dithioacrylsäureestern

Heavy Metal Chelates of α-Cyano-β-amino-dithioacrylates The inner metal chelates of Pd^II, Ni^II, Co^III, and Ag^I with α-cyano-β-amino-dithioacrylates have been prepared. The coordination of the dithioester group and the amine nitrogen (S/N-coordination) has been proved by the chemical shift of the S2p and N1s electron binding energies in the ESCA spectra.