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

The new ligands 2,6-bis[{2′-( N,N - dialkylaminomethyl ) phenylselanyl } methyl ]pyridine with the general formula 2,6-[{2′-(R 2 NCH 2 )C 6 H 4 }SeCH 2 ] 2 C 5 H 3 N [R = Me ( L1 ), Et ( L2 )], based on pyridine functionalized with organoselenium groups, were obtained by reacting 2-(R 2 NCH 2 )C 6 H 4 SeNa 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 = CF 3 SO 3 ), AgPF 6 and (C 6 F 5 )Au(tht) (tht = tetrahydrothiophene), when the metal complexes [AgL]X [X = OTf, L =  L1 ( 1 ), L2 ( 2 ); X  = PF 6, L =  L1 ( 3 ), L2 ( 4 )], [(C 6 F 5 Au) 2 L1 ] ( 5 ) and [(C 6 F 5 )Au L2 ] ( 6 ), were isolated. Multinuclear NMR spectroscopy ( 1 H, 13 C, 19 F, 31 P, 77 Se, 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)(1 κ1N1-2κ1Se2 ) 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.