Preparation of aryldiazene complexes of rhodium

Aryldiazene complexes [Rh(ArNNH)(CO)(PPh3)3]BF4 (1) and [Rh(ArNNH)(PPh3)4]BF4 (2) (Ar=C6H5 or 4-CH3C6H4) were prepared by allowing hydride species RhH(CO)(PPh3)3 and RhH(PPh3)4 to react with aryldiazonium cations at low temperature. The complexes were characterised by IR and 1H-, 31P- and 15N-NMR spectra, using 15N labelled compounds. Free aryldiazene ArNNH species and [Rh{PPh(OEt)2}4]BF4 were obtained by reacting the hydride RhH[PPh(OEt)2]4 with aryldiazonium cations in CH2Cl2 at −80°C. Reactions of aryldiazene complexes 1 and 2 with H2 (1 atm) were also studied, but did not lead to arylhydrazine derivatives.