Exploring the structure and redox activity of hexacoordinate bis(bipyridyl)silicon(IV) complexes. (7th July 2015) - Maguylo, Christina
Graphical abstract: The structures of a series of hexacoordinate bis(bipyridyl)silicon(IV) complexes are reported. The hexafluorophosphate salts of each complex cation exhibit a reversible, first reduction wave around −1 V (versus Fc + /Fc) in acetonitrile, nearly independent of the alkoxide or diolate substituent. The complexes with bidentate diolate ligands possess multiple, reversible reduction waves. Abstract: A series of hexacoordinate bis(bipyridyl)silicon(IV) complexes was synthesized by allowing [Si(bpy)2 I2 ]I2 to react with the alcohols or phenols: methanol, ethylene glycol, phenol, 2, 2′-biphenol, or 1, 2-benzendiol. Crystal structures were obtained for the corresponding complexes: [Si(bpy)2 (OMe)2 ] (I)(I3 ) (1 ), [Si(bpy)2 (-OCH2 CH2 O-)]I2 (2 ), [Si(bpy)2 (OPh)2 ](I3 )2 (3 ), [Si(bpy)2 (bph)](PF6 )2 (4 ), and [Si(bpy)2 (cat)](PF6 )2 (5 ), (bpy = 2, 2′-bipyridine, cat = 1, 2-benzenediolato, bph = 2, 2′-biphenolato ligand). All five complexes exist as distorted octahedral dications with readily exchangeable counterions. The hexafluorophosphate salts of each complex cation exhibit a reversible, first reduction wave around −1 V (versus Fc + /Fc) in acetonitrile, nearly independent of the alkoxide or diolate substituent. This is consistent with DFT calculations indicating a LUMO localized on the bipyridyl ligands. The complexes with bidentate diolate ligands possess multiple reversible reduction waves.