Reactions of [RuCl<sub>2</sub>(PPh<sub>3</sub>)<sub>3</sub>] with Nitron and with the “Enders Carbene”: Access to Ruthenium(III)
NHC Complexes
Sandra Hitzel
Christian Färber
Clemens Bruhn
Ulrich Siemeling
10.1021/om401058e.s001
https://acs.figshare.com/articles/journal_contribution/Reactions_of_RuCl_sub_2_sub_PPh_sub_3_sub_sub_3_sub_with_Nitron_and_with_the_Enders_Carbene_Access_to_Ruthenium_III_NHC_Complexes/2333395
The reactions of [RuCl<sub>2</sub>(PPh<sub>3</sub>)<sub>3</sub>] with the “Enders carbene”
1,3,4-triphenyl-1,2,4-triazol-5-ylidene
(<b>1</b>) and the “instant carbene” Nitron (<b>2</b>) respectively afforded the Ru<sup>II</sup> chelates [RuCl(<b>3</b>)(PPh<sub>3</sub>)<sub>2</sub>] (<b>3</b> = 3,4-diphenyl-1-<i>o</i>-phenylene-1,2,4-triazol-5-ylidene) and [RuCl(<b>4</b>)(PPh<sub>3</sub>)<sub>2</sub>] (<b>4</b> = 4-phenyl-3-phenylamino-1-<i>o</i>-phenylene-1,2,4-triazol-5-ylidene) in a process involving
the ortho metalation of the 1-Ph group of the respective carbene ligand.
It proved possible to synthesize [RuCl(<b>3</b>)(PPh<sub>3</sub>)<sub>2</sub>] more conveniently in higher yield by using the stable
carbene precursor 5-methoxy-1,3,4-triphenyl-4,5-dihydro-1<i>H</i>-1,2,4-triazole (MeO-<b>1</b>-H) instead of the free carbene <b>1</b> in the presence of triethylamine to trap the HCl generated
by the ortho metalation. Aerobic oxidation of the Ru<sup>II</sup> chelates
in the presence of chloride ions furnished [RuCl<sub>2</sub>(<b>3</b>)(PPh<sub>3</sub>)<sub>2</sub>] and [RuCl<sub>2</sub>(<b>4</b>)(PPh<sub>3</sub>)<sub>2</sub>], which are rare examples
of Ru<sup>III</sup> NHC complexes. The crystal structures of all four
complexes were determined by single-crystal X-ray diffraction studies.
In addition, the crystal structure of the hydrochloride of Nitron
was also determined. In the Ru<sup>II</sup> chelates, the pentacoordinate
metal center is in a distorted-square-pyramidal environment with the
carbon atom of the ortho-metalated 1-Ph group occupying the apical
position. The coordination sphere of the Ru<sup>III</sup> chelates
is complemented by a second chlorido ligand, which is positioned <i>trans</i> to this carbon atom.
2014-01-13 00:00:00
ortho metalation
pentacoordinate metal center
RuCl
carbon atom
RuII chelates
carbene
Nitron
RuIII NHC complexes