The Synthesis and Characterization of Re2(Xap)4Cl2 Compounds

Five dirhenium(III) compounds, Re2(3,5-(CH3)2ap)4Cl2 (1), Re2(ap)4Cl2 (2), Re2(3-MeOap)4Cl2 (3), Re2(3-Clap)4Cl2 (4), and Re2(3,5-Cl2ap)4Cl2 (5), were synthesized and characterized, where 3,5-(CH3)2ap, ap, 3-MeOap, 3-Clap and 3,5-Cl2ap are 2-(3,5-dimethylanilino)pyridinate, 2-anilinopyridinate, 2-(3-methoxyanilino)pyridinate, 2-(3-chloroanilino)pyridinate and 2-(3,5-dichloroanilino)pyridinate, respectively. Structural studies revealed the Re–Re bond lengths ranging from 2.2214(4) to 2.2262(11) Å, signifying that the dirhenium core maintains its quadruple bond. The asymmetric nature of 2-anilinopyridinate ligands resulted in several possible regioisomers: compounds 1 and 4 adopt a cis-(2,2) arrangement, while compounds 2 and 5 assume trans-(2,2) and (3,1) arrangements, respectively. All five compounds display three (quasi)reversible one electron couples, two oxidations and one reduction, and their electrode potentials correlate linearly with the Hammett constant of the aniline substituent.