Unsymmetrical Bis(iminoethyl)pyridine Metal Complexes with a Pendant Alkenyl Substituent. Part B: Internal Olefin Coordination to Ruthenium

A series of unsymmetrically substituted 2,6-bis(iminoethyl)pyridine ligands (5a−d), each bearing a 2,6-diisopropylphenyl group and a linear alkenyl group (allyl to hexenyl) at their pairs of imino nitrogen atoms, was reacted with ruthenium(II) reagents. The reaction of the allyl-substituted system 5a with the reagent [Ru(PPh₃)₃Cl₂] gave the [(κ³N,N′,N′′-chelate ligand)(PPh₃)RuCl₂] complex 6a, featuring a pair of cis chloride ligands. In contrast, the reactions of 5b−d with [RuCl₂(p-cymene)]₂ yielded the complexes 7b−d. They each feature a pair of trans chloride ligands and an internally coordinated η²-CHCH₂ group at the octahedrally coordinated ruthenium center. Treatment of 7c,d with PMe₃ resulted in a replacement of the internally coordinated π-olefin from ruthenium by the phosphine to yield the complexes 8c,d. The compounds 6a, 7b−d, and 8c,d were characterized by X-ray diffraction.