Isolation and structural comparison of RuII-dnp complexes [dnp = 2,6-bis(1,8-naphthyridin-2-yl)-pyridine] with axially or equatorially coordinating NCS ligands

The molecular and crystal structures of two ruthenium(II) complexes, viz. cis-aqua[2,6-bis(1,8-naphthyridin-2-yl) pyridine-kappa(3) N,N', N '']( thiocyanato- kappa N)(triphenylphosphine-kappa P)ruthenium(II) hexafluoridophosphate-acetone-water (1/0.5/1), [Ru(NCS)(C21H13N5)(C18H15P)(H2O)]PF6 center dot 0.5C(3)H(6)O center dot H2O (I) and trans-[2,6-bis(1,8-naphthyridin-2-yl)pyridine-kappa(3)'N, N',N '']bis( pyridine-kappa N)(thiocyanato-kappa N)ruthenium(II) thiocyanate, [Ru(NCS)(C21H13N5)(C5H5N)(2)]NCS (II), with an N-coordinating thiocyanato group and a tridentate polypyridyl supporting ligand, are reported. The Ru-II atom in each of the cationic complexes adopts a distorted octahedral coordination sphere, defined by an N atom of the thiocyanato ligand, three N atoms from the tridentate polypyridyl ligand, and an O and P atom in (I) or two pyridine-N atoms in (II) derived from monodentate ligands. The thiocyanato ligand in (I) coordinates in an axial manner to the {Rudnp} unit [dnp = 2,6-bis(1,8-naphthyridin-2-yl)pyridine], whereas it coordinates in an equatorial manner in (II). In the crystal structure of compound (I), intramolecular C-H center dot center dot center dot O, C-H center dot center dot center dot N and O-H center dot center dot center dot N hydrogen bonds as well as pi-pi contacts are present, in addition to intermolecular C-H center dot center dot center dot F, C-H center dot center dot center dot O and O-H center dot center dot center dot O hydrogen bonds. In the crystal structure of compound (II), intramolecular C-H center dot center dot center dot N hydrogen bonds are observed along with intermolecular C-H center dot center dot center dot N and C-H center dot center dot center dot S hydrogen bonds as well as a pi-pi interaction.