Heterocyclic-2-thione derivatives of metals incorporating cyclopalladated azobenzenes of variable nuclearity and N,S-bridged 1D polymer of [bis(pyridine-2-thiolato)mercury(II)]

In this investigation, the reactivity of azobenzene-based cyclopalladated precursors with a series of heterocyclic-2-thiones is described. Reactions of the precursor, [Pd-2(mu-Cl)(2) -(kappa(2):C,N-deazb)(2)], with pyridine-2-thione (pytH), or pyrimidine-2-thione (pymtH), yielded the red-brown dinuclear compounds [Pd-2(mu-N,S-pyt)(2)(kappa(2):C,N-deazb)(2)] (1) and [Pd-2(mu-N,S-pymt)(2)(kappa(2):C,N-deazb)(2)] (2) (deazbH = 4,4'-diethoxyazobenzene). A similar reaction of [Pd-2(mu-Cl)(2)(kappa(2):C,N-p-mazb)(2)] with N-phenyl-imidazolidine-2-thione (imdtH-NPh) yielded a trinuclear compound, [Pd-3(mu-N,S-imdt-NPh)(4)(kappa(2):C,N-pmazb)(2)] (4) (pmazb = p-methoxyazobenzene). A direct reaction of PdCl2 with azobenzene (azbH) and N-methyl-imidazolidine-2-thione (imdtH-NMe) afforded a mononuclear compound, [Pd(kappa S-1-imdtH-NMe)Cl(kappa(2):C,N-azb)] (3). In the compounds 1, 2 and 4, the thio-ligands, pyt(-), pymt(-) and imdt-NPh- are coordinating as anions with N,S-bridging (1, 2, 4) and in compound 3, imdtH-NMe is coordinating as a neutral ligand through the S-donor atom only. Compounds 1-4 are luminescent in the visible region. A reaction of HgCl2 with azobenzene (azbH), and pyridine-2-thione in DMF, did not yield the cyclometallated compound, [Hg-2(mu-N,S-pyt)(2)(kappa(2):C,N-azb)(2)]; rather, it afforded two coordinate compounds, [Hg(kappa S-1-pyt)(2)] (5), with polymerisation occurring via weak N center dot center dot center dot Hg bonds.