New C-tetrazolato complexes of rhodium(III), palladium(II) and gold(III)

The azido complexes [RhCp*(mu -N-3)(N-3)](2) (Cp* = eta -C5Me5), trans-Rh(N-3)(CO)(PPh3)(2), Na-2[Pd(N-3)(4)], Na-2[Pd-2(mu -N-3)(2)(N-3)(4)] and Na[Au(N-3)(4)], prepared in situ from metal halide precursors and a three- to ten-fold excess of NaN3 in water, react with aliphatic isocyanides to give a series of new metal-carbon bonded tetrazolato complexes. All azide ligands in the coordination sphere undergo this cycloaddition with isocyanides except on palladium(II) where only two tetrazol-5-ato groups are formed. In the neutral species HAu(CN4R)(4) (R = 'Bu (2c), Cy (2d)) presumably one of the four tetrazol-5-ato groups has been protonated to afford a tetrazol-5-ylidene (carbene) ligand. The reactivities of the isocyanides decrease in the order CN'Bu > CNCy > CN(CH2)(4)Cl > CN-allyl > CNCH2CO2Na; surprisingly, no reaction occurs with methylisocyanide. With tert-butyl isocyanide in the cold, [Ru(mu -N-3)(N-3)(eta -C10H14)](2) (C10H14:4-isopropyltoluene) only reacts with cleavage of the azido bridges giving rise to [Ru(N-3)(2)(eta -C10H14)CN'Bu] (5a), while heating of the same mixture affords a second azido-isocyanide complex, trans-[Ru(N-3)(2)(CN'Bu)(4)] (5b), of which an X-ray structure analysis has been carried out. In some cases the reactions proceed with N-2 evolution, and rhodium complexes 6a-c are also formed probably containing cyanamido (-N{R}C=N) or carbodiimido (-N=C=NR) ligands, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.