2,2'-Bipyridyl formation from 2-arylpyridines through bimetallic diyttrium intermediate.

An alkylyttrium complex supported by an ,'-bis(2,6-diisopropylphenyl)ethylenediamido ligand, (ArNCHCHNAr)Y(CHSiMe)(THF) (, Ar = 2,6- PrCH), activated an -phenyl C-H bond of 2-phenylpyridine () to form a (2-pyridylphenyl)yttrium complex () containing a five-membered metallacycle. Subsequently, a unique C(sp)-C(sp) coupling of 2-phenylpyridine proceeded through a bimetallic yttrium intermediate, derived from an intramolecular shift of the yttrium center to an -position of the pyridine ring in , to yield a bimetallic yttrium complex () bridged by two-electron reduced 6,6'-diphenyl-2,2'-bipyridyl. Aryl substituents at the -position of the pyridine ring were key in order to destabilize the μ,κ-(C,N)-pyridyldiyttrium intermediate prior to the C(sp)-C(sp) bond formation.