Solid-state and solution characterization of half-sandwich Ru(II) complexes with carboxylic ligands containing N-based coordinating functions

• Half-sandwich Ru(II) complexes containing isonicotinic acid and aminobenzoic acids.
• The solid state packings are governed by extended hydrogen-bond networks.
• Ligand solvolysis has been observed in dmso and acetonitrile.

The aminobenozic ligands 3-(4-aminophenyl)propionic acid (4APPA), 4-(4-aminophenyl)butyric acid (4APBA) and 5-aminoisophthalic acid (5AIPA) have been reacted with [(η6-p-cymene)RuCl2]2 giving rise to the corresponding half-sandwich Ru(II) complexes of formula [(η6-p-cymene)Ru(ligand)Cl2] (1, 2 and 3, respectively). The solid state structures of all three organometallic compounds have been elucidated by single crystal X-ray analysis conducted on crystals grown in MeOH or THF. The aminobenzoic ligands interact with the metal through the amine function, the pseudo-octahedral geometry being satisfied by a η6-coordinated p-cymene ring and by two chloride ligands. Dissolution of the complexes in coordinating solvents, such as dmso or acetonitrile led to ligand solvolysis, as evidenced by 1H NMR analysis. The lability of monodentate N-based ligands toward the organometallic fragment [(η6-p-cymene)RuCl2] was evidenced by the structural outcomes deriving from crystals grown in acetonitrile of the related compounds [(η6-p-cymene)Ru(INA)Cl2] (4) (INA = isonicotinic acid) and [(η6-p-cymene)Ru(4ABA)Cl2] (5) (4ABA = 4-aminobenzoic acid). These revealed, although in low yields, the occurred ligand solvolysis with formation of a cocrystal of formula {[(η6-p-cymene)Ru(INA)Cl2](H2O) (INA)} in the case of complex 4 and formation of the tetrakis–acetonitrile complex trans-[Ru(CH3CN)4Cl2] in the case of complex 5.

The crystallization solvent can have a profound effect on the structural outcome for half-sandwich Ru(II) complexes containing aminobenzoic acids or isonicotinic acid. In coordinating solvents such as dmso or acetonitrile ligand solvolysis can be observed, while in less coordinating solvents such as methanol, THF or dichloromethane the complexes remain intact.Figure optionsDownload as PowerPoint slide