2011-08, Kessler, Florian, Wuttke, Evelyn, Lehr, Daniela, Wang, Yan, Weibert, Bernhard, Fischer, Helmut

2008, Pui, Aurel, Fischer, Helmut, Kopf, Henning

A series of R-Salophen manganese(III) and iron(III) complexes, where R = OH, OCH3 or COOH, and Salophen is bis(salicylaldehyde)-N,N’-o-phenylendiimine, have been obtained. The synthesis and characterization by elemental analyses, 1H NMR, UV-VIS, FT IR, ESMS spectroscopy and cyclic voltammetry of the ligands and some complexes of Mn(III) and Fe(III) with R-Salophen are presented in this study.

2008, Mohamed, Gehad G., Szesni, Normen, Fischer, Helmut

The fragmentation pathways of allenylidene and carbene complexes have been studied using FAB mass spectrometry in comparison with thermal analyses (TGA, DrTG and DTA). Both the decomposition modes are investigated and the possible fragmentation pathways are suggested. The use of mass and thermal analyses (TGA and DTA) in the analyses of allenylidene and carbene complexes allowed the characterization of the fragmentation pathways in MS. The major pathway includes successive loss of carbon monoxide followed by fragmentation of the organic part of the allenylidene or carbene molecules. This is also confirmed by thermogravimetric analysis (TGA) where the first step involves the loss of carbon monoxide followed by the organic ligand. The nature of each step; exothermic or endothermic, is also studied using DTA technique. The kinetic parameters of the thermal decomposition are also studied using the Coates-Redfern method.

2007, Pietraszuk, Cezary, Fischer, Helmut, Marciniec, Bogdan

2011-02, Haas, Thomas, Kaspar, Katrin, Forner, Konstanze, Drexler, Matthias, Fischer, Helmut

2008, Fischer, Helmut

2008, Dragutan, Ileana, Dragutan, Valerian, Fischer, Helmut

2011, Reichmann, Bernhard, Drexler, Matthias, Weibert, Bernhard, Szesni, Normen, Strittmatter, Tobias, Fischer, Helmut

The reaction of the bis(amino)allenylidene complex [(CO)₅W═C═C═C(NMe₂)₂] with diethyldiazomethane yields two products, a cyclic carbene complex (2) by 1,2-addition of Et₂C−N₂ to the C_α−C_β bond of the allenylidene ligand and the η¹-butatriene complex [(CO)₅W{C[C(NMe₂)₂]═C═CEt₂}] (3). Complex 2 slowly eliminates N₂ and rearranges into 3. In contrast, only η¹-butatriene complexes, [(CO)₅M{C[C(NMe₂)XR]═C═C(R′)₂}], are isolated from the reaction of diazoalkanes (R′)₂C−N₂ (R′ = Me, Et, ⁿPr) with alkoxy(amino)allenylidene complexes [(CO)₅M═C═C═C(NMe₂)OR] (M = Cr, W; R = Me, Et, (−)-menthyl) or with the (alkylthio)(amino)allenylidene complex [(CO)₅W═C═C═C(NMe₂)SⁿPr]. These new η¹-butatriene complexes are related to C_α phosphine adducts of allenylidene complexes such as [(CO)₅W{C(PMe₃)═C═C(NMe₂)Ph}] (17) and might be regarded as C_α carbene adducts. However, the PMe₃ substituent in 17 is not replaced when 17 is treated with an N-heterocyclic carbene. Vice versa, the “carbene” substituent “C(NMe₂)OEt” in the η¹-butatriene complex [(CO)₅Cr{C[C(NMe₂)OEt]═C═CEt₂}] is not replaceable by PMe₃. Free N-heterocyclic carbenes do not add to the C_α atom of the allenylidene complex [(CO)₅W═C═C═C(C₆H₄NMe₂-p)₂] but instead to the C_γ atom, giving the dipolar neutral alkynyl complexes [(CO)₅W−C≡CC(C₆H₄NMe₂-p)₂L] (L = SIMe, SIMes). DFT calculations on the reaction mechanism indicate that a cyclic carbene complex and two isomeric η²-butatriene complexes are intermediates in the reaction pathway to form η¹-butatriene complexes. The structure of two representative examples of η¹-butatriene complexes and of one C_γ carbene adduct has been established by X-ray structure analyses.

2008, Dragutan, Valerian, Dragutan, Ileana, Fischer, Helmut

2007, Kessler, Florian, Szesni, Normen, Maaß, Chaya, Hohberger, Christiane, Weibert, Bernhard, Fischer, Helmut