<i>trans</i>-[Ru<sup>II</sup>(dpp)Cl<sub>2</sub>]: A Convenient Reagent for the
Preparation of Heteroleptic
Ru(dpp) Complexes, Where dpp Is 2,9-Di(pyrid-2′-yl)-1,10-phenanthroline
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Abstract
The reaction of 2,9-di(pyrid-2′-yl)-1,10-phenanthroline
(dpp) with [RuCl<sub>3</sub>·3H<sub>2</sub>O] or [Ru(DMSO)<sub>4</sub>Cl<sub>2</sub>] provides the reagent <i>trans</i>-[Ru<sup>II</sup>(dpp)Cl<sub>2</sub>] in yields of 98 and 89%, respectively.
This reagent reacts with monodentate ligands L to replace the two
axial chlorides, affording reasonable yields of a ruthenium(II) complex
with dpp bound tetradentate in the equatorial plane. The photophysical
and electrochemical properties of the tetradentate complexes are strongly
influenced by the axial ligands with electron-donating character to
stabilize the ruthenium(III) state, shifting the metal-to-ligand charge-transfer
absorption to lower energy and decreasing the oxidation potential.
When the precursor <i>trans</i>-[Ru<sup>II</sup>(dpp)Cl<sub>2</sub>] reacts with a bidentate (2,2′-bipyridine), tridentate
(2,2′;6,2″-terpyridine), or tetradentate (itself) ligand,
a peripheral pyridine on dpp is displaced such that dpp binds as a
tridentate. This situation is illustrated by an X-ray analysis of
[Ru(dpp)(bpy)Cl](PF<sub>6</sub>)
