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

The mol-ecular and crystal structures of two ruthenium(II) complexes, viz. cis-aqua-[2,6-bis-(1,8-naphthyridin-2-yl)pyridine-κ(3) N,N',N''](thio-cyanato-κN)(tri-phen-yl-phosphine-κP)ruthenium(II) hexa-fluorido-phosphate-acetone-water (1/0.5/1), [Ru(NCS)(C(21)H(13)N(5))(C(18)H(15)P)(H(2)O)]PF(6)·0.5C(3)H(6)O·H(2)O (I) and trans-[2,6-bis-(1,8-naphthyridin-2-yl)pyridine-κ(3)'N,N',N'']bis-(pyridine-κN)(thiocyanato-κN)ruthenium(II) thio-cyanate, [Ru(NCS)(C(21)H(13)N(5))(C(5)H(5)N)(2)]NCS (II), with an N-coordinating thio-cyanato group and a tridentate polypyridyl supporting ligand, are reported. The Ru(II) atom in each of the cationic complexes adopts a distorted octa-hedral coordination sphere, defined by an N atom of the thio-cyanato 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 thio-cyanato ligand in (I) coordinates in an axial manner to the {Ru-dnp} 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), intra-molecular C-H⋯O, C-H⋯N and O-H⋯N hydrogen bonds as well as π-π contacts are present, in addition to inter-molecular C-H⋯F, C-H⋯O and O-H⋯O hydrogen bonds. In the crystal structure of compound (II), intra-molecular C-H⋯N hydrogen bonds are observed along with inter-molecular C-H⋯N and C-H⋯S hydrogen bonds as well as a π-π inter-action.