New ruthenium(II) complexes with enantiomerically pure bis- and tris(pinene)-fused tridentate ligands. Synthesis, characterization and stereoisomeric analysis

A new set of Ru-Cl complexes containing either the pinene[5,6]bpea ligand (L1) or the C3 symmetric pinene[4,5]tpmOMe (L2) tridentate ligand in combination with the bidentate (B) 2,2′-bipyridine (bpy) or 1,2-diphenylphosphinoethane (dppe) with general formula [RuCl(L1 or L2)(B)]⁺ have been prepared and thoroughly characterized. In the solid state, X-ray diffraction analysis techniques have been used. In solution, cyclic voltammetry (CV) and 1D and 2D NMR spectroscopy have been employed. DFT calculations have been also performed on these complexes and their achiral analogues previously reported in our group, to interpret and complement experimental results. Whereas isomerically pure complexes ([Ru^IICl(L2)(bpy)](BF₄), 5 and [Ru^IICl(L2)(dppe)](BF₄), 6) are obtained when starting from the highly symmetric [Ru^IIICl₃(L2)], 2, isomeric mixtures of cis,fac-[Ru^IICl(L1)(bpy)](BF₄) (3b/3b’), trans,fac- (3a) and up/down,mer- (3c, 3d) isomers are formed when bpy is added to the less symmetric [Ru^IIICl₃(L1)], 1, in contrast to the case of the bulky dppe ligand that, upon coordination to 1, leads to the trans,fac-[Ru^IICl(L1)(dppe)](BF₄) (4a) complex as a sole isomer due to steric factors.