<p>A
series of water soluble arene-ruthenium(II) complexes [(<i>η</i><sup>6</sup>-arene)RuCl(κ<sup>2</sup>-L)]<sup>n+</sup> (n = 0, 1) (<b>[Ru]-1</b> – <b>[Ru]-12</b>) containing pyridine based N,O or N,N ligands (<b>L1-L6</b>) were synthesized and employed
for the catalytic C-H bond activation/ arylation of 2-phenylpyridine with aryl
halides in water. Efficient C-H bond activation/ arylation of a wide range of
substituted 2-phenylpyridines and aryl halides were achieved to afford corresponding
mono and biarylated products. Exploring the reactivity of the synthesized
complexes, our investigation with ruthenium catalysts inferred that pyridine
based N,O donor ligands afforded enhanced catalytic activity compared to those
obtained with the iminopyridine (N,N donor) ligands. Further, mass
spectrometric investigations, during the catalytic and controlled reaction
conditions, evidenced the presence of the crucial cycloruthenated species {(<i>η</i><sup>6</sup>-<i>p</i>-cymene)Ru(<i>κ</i><sup>2</sup>-<i>CN</i>-phenylpyridine)}<sup>+</sup> (m/z [M<sup>+</sup>]
390.0), along with a ligand coordinated species, {(<i>η</i><sup>6</sup>-<i>p</i>-cymene)Ru(<b>L1</b>)(<i>κ</i><sup>2</sup>-<i>CN</i>-phenylpyridine)}<sup>+</sup> (m/z [M<sup>+</sup>]+Na
539.0), suggesting the important role such intermediate species in C-H bond
activation reactions. Moreover, molecular structures for few of the representative
complexes were also authenticated by single crystal X-ray diffraction studies.</p>
Nickel-catalyzed C–N bond activation: activated primary amines as alkylating reagents in reductive cross-coupling