A paramagnetic trigonal paddlewheel complex with iron-dithiolato ligand paddles: {[(C 9H 18N 2S 2)Fe(NO)] 3Ag 2}(BF 4) 2

Abstract

Addition of AgBF 4 to (bme-dach)Fe(NO), (bme-dach, N, N′-bis(2-mercapto-ethyl)-1,4-diazacycloheptane) affords a pentametallic C 3 paddlewheel complex, {[(bme-dach)Fe(NO)] 3Ag 2}[BF 4] 2, resulting from the ability of the thiolate sulfurs of the N 2S 2 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 Ag 2 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 1.17 emu-K/mol with the presence of weak ferromagnetic coupling evident at temperatures less than 20 K. To our knowledge this is the first example of a paddlewheel complex in which paramagnetism exists within the bridging bidentate ligand “paddles”.