You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Direct observation of a bent carbonyl ligand in a 19-electron transition metal complex. The 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.
{"Chemical": ["CH2Cl2", "[CpRu(CO)2]2", "CpRu(CO)2(\u2022)", "ruthenium", "[CpFe(CO)2]2", "CpRu(CO)2P(OMe)3(\u2022)", "CO", "transition metal", "[CpRu(CO)]2(\u03bc-CO)", "P(OMe)3", "CpFe(CO)2P(OMe)3(\u2022)", "carbonyl", "Fe-C-O"]}