Synthesis, spectra and electrochemistry of dinitro-bis- {2-(phenylazo)pyrimidine} ruthenium(II). Nitro–nitroso derivatives and reactivity of the electrophilic nitrosyl centre

Silver-assisted aquation of blue cis-trans-cis-RuCl2(Raapm)2 (1a–1e) leads to the synthesis of solvento species, blue-violet cis-trans-cis-[Ru(OH2)2(Raapm)2](ClO4)2 [Raapm = p-R-C6H4-N=N-C4H3- NN, (2a–2e), abbreviated as N,N-chelator, where N(pyrimidine) and N(azo) represent N and Nrespectively; R = H (a), p-Me (b), p-Cl (c), m-Me (d), m-Cl (e) that react with NO2 in warm EtOH to give violet dinitro complexes of the type, Ru(NO2)2(Raapm)2 (3a–3e). The nitrite complexes are useful synthons of electrophilic nitrosyls, and on triturating the dinitro compounds with conc. HClO4, nitro-nitrosyl derivatives are isolated. The solution structure and stereoretentive transformation in each step have been established from 1H NMR results. The compounds are redox active and display one metal-centred oxidation and successive ligand-based reductions. The n (NO) >1900 cm–1 strongly suggests the presence of linear Ru– N–O bonding. The electrophilic behaviour of metal-bound nitrosyl has been proved in one case by reacting with a bicyclic ketone, camphor, containing an active methylene group and an arylhydrazone with an active methine group. Diazotization of primary aromatic amines with strongly electrophilic mononitrosyl complexes in acetonotrile and dichloromethane solutions has been thoroughly studied.