NbCl₅·(N,N′-dicyclohexylurea) 1a owns a distorted octahedral structure due to intramolecular NH⋯Cl bonding. The unit cell contains four units which are intermolecularly NH⋯Cl and NH⋯N bonded. An extended intramolecular network of H-bonding (N–H⋯Cl, CH⋯Cl, CH⋯N) causes the 3D self assembling of the units. Upon addition of base, the HCl release from 1a is observed with the transfer to Nb of the O-atom of the carbonylic function of the starting urea which is converted into the relevant carbodiimide CyNCNCy 4. The latter is quantitatively released by adding an excess of NEt₃ at 308 K (py and DBU are less efficient) with formation of the known NbOCl₃(NEt₃)₂ , isolated in quantitative yield. Increasing the temperature leads to a loss in selectivity as the formed DCC undergoes further reactions. At 350 K, the isocyanate CyNCO has been isolated in 60% yield besides a mixture of Nb-complexes. DFT calculations have been coupled to IR and NMR experiments for characterizing possible reaction intermediates and the behaviour of 1a. Several other MCl_x species (ScCl₃,YCl₃,LaCl₃,TiCl₄ , TaCl₅ , AlCl₃ , SnCl₄ ) have been shown to be able to co-ordinate DCU but not all of them promote the conversion of urea into DCC.

The temperature dependence of the quantized voltage steps near the superconducting transition temperature of $\mathrm{Nb}∕\mathrm{Al}–\mathrm{Al}{\mathrm{O}}_x∕\mathrm{Nb}$ overdamped Josephson junctions irradiated at $75\mathrm{GHz}$ has been studied. These junctions can switch between the hysteretic and nonhysteretic regime either by varying a fabrication parameter or, as shown in the present paper, by changing the junction operating temperature. Due to the high values of $J_C$ and $V_C$ up to $75\mathrm{kA}∕{\mathrm{cm}}^2$ and $0.5\mathrm{mV}$ at $4.2\mathrm{K}$ , respectively, and to the moderate temperature dependence of these parameters, the height of the first rf-induced step was larger than $1\mathrm{mA}$ at $T=6–8\mathrm{K}$ , corresponding to $0.7–0.9T∕T_C$ on a junction of $5\times 5\mu {\mathrm{m}}^2$ . The flatness at the nanovolt level of this step demonstrates the feasibility of programable or ac voltage standards operating in a cryocooler setup.