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

Abstract

The mol-ecular and crystal structures of two ruthenium(II) complexes, viz. cis-aqua-[2,6-bis-(1,8-naphthyridin-2-yl)pyridine-κ³ N,N',N''](thio-cyanato-κN)(tri-phen-yl-phosphine-κP)ruthenium(II) hexa-fluorido-phosphate-acetone-water (1/0.5/1), [Ru(NCS)(C₂₁H₁₃N₅)(C₁₈H₁₅P)(H₂O)]PF₆·0.5C₃H₆O·H₂O (I) and trans-[2,6-bis-(1,8-naphthyridin-2-yl)pyridine-κ³'N,N',N'']bis-(pyridine-κN)(thiocyanato-κN)ruthenium(II) thio-cyanate, [Ru(NCS)(C₂₁H₁₃N₅)(C₅H₅N)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.

Keywords: crystal structure; polypyridine; ruthenium complex; thio­cyanato ligand; tridentate ligand.