10.1021/jp311732t.s001
Justin
P. Lomont
Justin
P.
Lomont
Son C. Nguyen
Son C.
Nguyen
Charles B. Harris
Charles B.
Harris
Direct Observation of a Bent Carbonyl Ligand in a
19-Electron Transition Metal Complex
American Chemical Society
2013
CO ligand
electron
picosecond time scale
adduct
Bent Carbonyl Ligand
CH
DFT
CpRu
TRIR spectra
2013-03-21 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Direct_Observation_of_a_Bent_Carbonyl_Ligand_in_a_19_Electron_Transition_Metal_Complex/2432092
The photochemistry
of [CpRu(CO)<sub>2</sub>]<sub>2</sub> in P(OMe)<sub>3</sub>/CH<sub>2</sub>Cl<sub>2</sub> solution has been studied using
picosecond time-resolved infrared (TRIR) spectroscopy. Photolysis
at 400 nm leads to the formation of 17-electron CpRu(CO)<sub>2</sub><sup>•</sup> radicals, which react on the picosecond time
scale to form 19-electron CpRu(CO)<sub>2</sub>P(OMe)<sub>3</sub><sup>•</sup> adducts. The TRIR spectra of this adduct display an
unusually low CO stretching frequency for the antisymmetric CO stretching
mode, suggesting that one carbonyl ligand adopts a bent configuration
to avoid a 19-electron count at the metal center. This spectral assignment
is supported by analogous experiments on [CpFe(CO)<sub>2</sub>]<sub>2</sub> in the same solvent, combined with DFT studies on the structures
of the 19-electron adducts. The DFT results predict a bent CO ligand
in CpRu(CO)<sub>2</sub>P(OMe)<sub>3</sub><sup>•</sup>, whereas
approximately linear Fe–C–O bond angles are predicted
for CpFe(CO)<sub>2</sub>P(OMe)<sub>3</sub><sup>•</sup>. The
observation of a bent CO ligand in the 19-electron ruthenium adduct
is a surprising result, and it provides new insight into the solution-phase
behavior of 19-electron complexes. TRIR spectra were also collected
for [CpRu(CO)<sub>2</sub>]<sub>2</sub> in neat CH<sub>2</sub>Cl<sub>2</sub>, and it is interesting to note that no singly bridged [CpRu(CO)]<sub>2</sub>(μ-CO) photoproduct was observed to form following 400-
or 267-nm excitation, despite previous observations of this species
on longer time scales.