A series of iron(II) dihalogenide complexes with two different bisphosphinoethane ligands is reported. In the case of 1,2bis(diphenylphosphanyl)ethane (dppe), depending on the stoichiometry, the tetrahedral [(μ-dppe)FeCl 2 ] n and octahedral trans-[(dppe) 2 FeCl 2 ] complexes are formed. The polymeric complex [(μ-dppe)FeCl 2 ] n , with iron in a tetrahedral environment, preferentially reacts with chelating amines to give the octahedral diphosphine complex, trans-[(dppe) 2 -FeCl 2 ], and different octahedral amine complexes. With the [a]141 sterically more demanding 1,2-bis(diisopropylphosphanyl)ethane (dippe), the monomeric and tetrahedral halogen complexes [(dippe)FeX 2 ] are exclusively obtained (X = Cl, Br). These complexes react with chelating amines in a similar manner, to give free ligand and the corresponding octahedral amine complex. The present results suggest that the diphosphines in the investigated iron(II) complexes are bound too weakly to form productive catalyst precursors.

Nuclear magnetic resonance spectroscopy has proven to be powerful for the study of dynamic processes. A new pulse sequence, SirX, is designed to provide boundary conditions that simplify the McConnell equations. Both an initial rate approximation and a whole curve fitting to the time course of magnetization can be used to calculate the exchange rate. These methods were used to study the exchange kinetics of N,N-dimethylacetamide. As compared with the well-established exchange spectroscopy suitable to studies of slow exchange, SirX has the advantage of being less time consuming and capable of providing more reliable kinetic data. Furthermore, by setting the observation on X-nuclei with larger chemical shift dispersion as compared with an observation on (1)H resonance, SirX extends the upper limit of a reliable determination of exchange rates.

Epitaxial layers of GaN have been grown on {1102} sapphire in atmospheric OMCVD system using Ga(CH3)3 · N(CH3)3 adduct and NH3 as reactants. Optimum growth conditions for crystallographically perfect layers have been found at temperatures between 850 and 1000 °C. With increasing temperature the growth rate decreases whereas the concentration of free carriers increases. In photoluminescence spectra only the donor‐acceptor pair recombination could be found. It is concluded that the donor oxygen (ON) and the acceptor carbon (CN) are the dominant impurities.