Photochemistry and Matrix-isolated Species

Photochemistry and Matrix-isolated Species.—A potentially important development can be recognized in studies of the production of metal atoms and naked metal clusters e.g., Fcs from [Fe3(CO)i2] in the gas phase at ambient temperature by photodissociation or as a result of dissociation of metal carbonyls caused by metastable noble gases. In addition to ground-state species, significant numbers of excited-state atoms, many with long radiative lifetimes, can be produced by these methods. 

The development of a low-temperature solution chemistry of species such 

Photolysis of [Mn(CO)5X] (X=C1, Br, I) in argon or methane matrices at 12 K has provided evidence for the formation of trigonal bipyramidal [Mn(CO)4X] in which X is equatorial, the same intermediate is involved in the nucleophilic substitution reactions of [Mn(CO 6X] in solution. 

It has been suggested that the excited-state species formed in the photolysis of [Mna(CO)io] with CCI4 in cyclohexane solution might be [MnaCCO) -Oua-CO)] or [Mna(CO)8(/ 2-CO)a], which do not contain a Mn—Mn bond. Preferential cleavage of a M—CO bond rather than a M—M bond in the rate determining step is supported by the results of studies of the thermal substitution reactions of [MnRe(CO)io], and the photosubstitution reactions of 

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