A paramagnetic trigonal paddlewheel complex with iron-dithiolato ligand paddles: {[(C9H18N2S2)Fe(NO)]3Ag2}(BF4)2

Abstract: Addition of AgBF4 to (bme-dach)Fe(NO), (bme-dach, N,N′-bis(2-mercapto-ethyl)-1,4-diazacycloheptane) affords a pentametallic C3 paddlewheel complex, {[(bme-dach)Fe(NO)]3Ag2}[BF4]2, resulting from the ability of the thiolate sulfurs of the N2S2 complex to serve as a bidentate bridging ligand to Ag+ ions. Single crystal X-ray analysis reveals the NO ligands coordinated to each Fe are all pointed in the same direction, resulting in a threefold rotation axis and a pseudo-mirror plane bisecting the Ag⋯Ag axis in the asymmetric unit cell. This Ag2 trigonal paddlewheel complex of non-bonded Ag⋯Ag average distance=2.866(3)Ǻ has also been characterized by infrared and UV–vis spectroscopies. The complex shows paramagnetism both in solution (Evans’ method) and in the solid state due to three S=½ {Fe(NO)}7 units. The EPR spectrum shows a single isotropic signal with g =2.024. SQUID analysis confirms this paramagnetism yielding a χT value of 1.17emu-K/mol with the presence of weak ferromagnetic coupling evident at temperatures less than 20K. To our knowledge this is the first example of a paddlewheel complex in which paramagnetism exists within the bridging bidentate ligand “paddles”. [Copyright &y& Elsevier]