ja3005682_si_002.pdf (317.3 kB)
Synthesis and N–H Reductive Elimination Study of Dinuclear Ruthenium Imido Dihydride Complexes
journal contribution
posted on 2012-10-17, 00:00 authored by Shin Takemoto, Yusuke Yamazaki, Takahiro Yamano, Daichi Mashima, Hiroyuki MatsuzakaDiruthenium imido dihydride complexes [(Cp*Ru)2(μ-NAr)(μ-H)2] (Ar = Ph (2a), p-MeOC6H4 (2b), p-ClC6H4 (2c), 2,6-Me2C6H3 (2d); Cp* = η5-C5Me5) have been synthesized by hydrogenation
of
the corresponding bis(amido) complexes [Cp*Ru(μ-NHAr)]2 (1a–d). Reductive elimination of
the N–H bond from 2a–c in
the presence of arene yields the amido hydride complexes [(Cp*Ru)2(μ-NHAr)(μ-H)(μ-η2:η2-arene)] containing a π-bound arene. The rate and kinetic
isotope effect for this reaction are consistent with a mechanism involving
initial rate-determining reductive elimination of an N–H bond
to produce the coordinatively unsaturated amido hydride species {(Cp*Ru)2(μ-NHAr)(μ-H)} (A) followed by rapid
trapping of this species by an arene. The existence of A is also supported by the reversible interconversion of [(Cp*Ru)2(μ-NHPh)(μ-H)(μ-η2:η2-C7H8)] with the tetranuclear complex
[(Cp*Ru)4(μ4-NHPh)(μ-NHPh)(μ-H)2] (4), a dimerization product of A through a μ4-NHPh bridge. DFT calculations provide
structures of A and transition states for the N–H
reductive elimination. Two distinct reaction pathways are found for
the N–H reductive elimination, one of which involves direct
migration of a μ-hydride to the μ-NAr ligand, and the
other involves formation of a transient terminal hydride species.
