jp311732t_si_001.pdf (175.91 kB)
Direct Observation of a Bent Carbonyl Ligand in a 19-Electron Transition Metal Complex
journal contribution
posted on 2013-03-21, 00:00 authored by Justin
P. Lomont, Son C. Nguyen, Charles B. HarrisThe photochemistry
of [CpRu(CO)2]2 in P(OMe)3/CH2Cl2 solution has been studied using
picosecond time-resolved infrared (TRIR) spectroscopy. Photolysis
at 400 nm leads to the formation of 17-electron CpRu(CO)2• radicals, which react on the picosecond time
scale to form 19-electron CpRu(CO)2P(OMe)3• 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)2]2 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)2P(OMe)3•, whereas
approximately linear Fe–C–O bond angles are predicted
for CpFe(CO)2P(OMe)3•. 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)2]2 in neat CH2Cl2, and it is interesting to note that no singly bridged [CpRu(CO)]2(μ-CO) photoproduct was observed to form following 400-
or 267-nm excitation, despite previous observations of this species
on longer time scales.
