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 (<b>5a</b>−<b>d</b>), 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 <b>5a</b> with the reagent [Ru(PPh<sub>3</sub>)<sub>3</sub>Cl<sub>2</sub>] gave the [(κ<sup>3</sup><i>N</i>,<i>N</i>′,<i>N</i>′′-chelate ligand)(PPh<sub>3</sub>)RuCl<sub>2</sub>] complex <b>6a</b>, featuring a pair of cis chloride ligands. In contrast, the reactions of <b>5b</b>−<b>d</b> with [RuCl<sub>2</sub>(<i>p</i>-cymene)]<sub>2</sub> yielded the complexes <b>7b</b>−<b>d</b>. They each feature a pair of trans chloride ligands and an internally coordinated η<sup>2</sup>-CHCH<sub>2</sub> group at the octahedrally coordinated ruthenium center. Treatment of <b>7c</b>,<b>d</b> with PMe<sub>3</sub> resulted in a replacement of the internally coordinated π-olefin from ruthenium by the phosphine to yield the complexes <b>8c</b>,<b>d</b>. The compounds <b>6a</b>, <b>7b</b>−<b>d</b>, and <b>8c</b>,<b>d</b> were characterized by X-ray diffraction.