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Laser flash photolysis of a chromium carbene complex: Pentacarbonyl(1,3‐dimethyl‐4‐imidazolin‐2‐ylidene)chromium(0)
Author(s) -
Oishi Shigero,
Tokumaru Katsumi
Publication year - 1989
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610020404
Subject(s) - flash photolysis , chemistry , carbene , chromium , photodissociation , photochemistry , ligand (biochemistry) , benzene , reactivity (psychology) , molecule , kinetics , reaction rate constant , organic chemistry , catalysis , medicine , biochemistry , physics , receptor , alternative medicine , pathology , quantum mechanics
Photoreactions of Cr(CO) 5 (Im) (Im = 1,3‐dimethyl‐4‐imidazolin‐2‐ylidene) have been investigated by laser flash and continuous photolysis. Quantum yields for the disappearance of Cr(CO) 5 (Im) in benzene under Ar or CO were very low, although transients observed by laser flash photolysis reacted rapidly with CO. This suggests that photodissociation of the carbene ligand is very minor. The laser flash photolysis at 337 nm in benzene (B) gave a transient (λ max = 630 nm), which converted to the second transient (λ max = 455 nm) within ∼100 ns. The kinetic studies of these transients revealed that the first one is a ‘free’ coordinatively unsaturated species (Cr(CO) 4 (Im)) and the second one carries a solvent molecule as a ligand (Cr(CO) 4 (Im)(B)). From the comparison of Cr(CO) 4 (Im) and Cr(CO) 5 , apparently lower reactivity of Cr(CO) 5 was found to be due to the strong coordination of a solvent molecule. The Im ligand neutralizes the deficit of electron density on Cr. A simple synthesis of Cr(CO) 5 (Im) was also described.