Silver(I) and gold(I) complexes of multidentate ligands based on functionalized pyridine

Abstract

The new ligands 2,6-bis[{2′-(N,N-dialkylaminomethyl)phenylselanyl}methyl]pyridine with the general formula 2,6-[{2′-(R2NCH2)C6H4}SeCH2]2C5H3N [R = Me (L1), Et (L2)], based on pyridine functionalized with organoselenium groups, were obtained by reacting 2-(R2NCH2)C6H4SeNa with 2,6–bis(bromomethyl)pyridine in 2:1 molar ratio. The coordination behaviour of the potentially multidentate ligands was investigated towards gold(I) and silver(I) in reactions with AgOTf (OTf = CF3SO3), AgPF6 and (C6F5)Au(tht) (tht = tetrahydrothiophene), when the metal complexes [AgL]X [X = OTf, L = L1 (1), L2 (2); X = PF6, L = L1 (3), L2 (4)], [(C6F5Au)2L1] (5) and [(C6F5)AuL2] (6), were isolated. Multinuclear NMR spectroscopy (1H, 13C, 19F, 31P, 77Se, as appropriate) and mass spectrometry were employed to investigate the two ligands and the metal complexes in solution. The single crystal X-ray diffraction studies revealed a N,Se,N,Se,N-monometallic pentaconnective (κ2Se1,Se2-κ3N1,N2,N3) coordination behaviour of L1 in 1, a Se,N- bimetallic biconnective (bridging) [μ(Au-Au)(1κ1N1-2κ1Se2) coordination behaviour of L1 in 5 and a Se,N,Se-monometallic triconnective (pincer like, κ2Se1,Se2-κN1) pattern of L2 in 6, while in the free ligands the nitrogen atoms of the two pendant arms are intramolecularly coordinated to selenium. In solid state, both 5 and 6 display metallophilic Au‧‧‧Au interactions.