Temperature- and wavelength-dependent photochemistry of [Cr(CO)5-(NMe3)] in argon and xenon matrices. Evidence for the formation of [Cr(CO)5] and novel [Cr(CO)4(NMe3)] complexes with three different types of symmetry
Abstract
Photolysis of [Cr(CO)5(NMe3)] in Ar and Xe matrices at 10 K with λ= 229 and 254 nm results in nearly quantitative formation of Cs[Cr(CO)4(NMe3)]. The reaction can be reversed by irradiation with λ= 546 nm. At 40 K in Xe isomerization of Cs[Cr(CO)4(NMe3)] into C3v[Cr(CO)4(NMe3)] or C2v[Cr(CO)4(NMe3)] has been detected. Long-wavelength photolysis with λ= 366, 405, and 436 nm results in release of the ligand NMe3. Besides Cr(CO)5⋯ X (X = Ar or Xe) a new species Cr(CO)5⋯ NMe3 is obtained. The lifetime of the excited states of [Cr(CO)5(NMe3)] appears to be longer than those for [Cr(CO)5(py)] and [Cr(CO)5(pyz)](py = pyridine, pyz = pyrazine). An explanation is given for the observed influence of wavelength, matrix, ligand, and temperature on the photochemical behaviour. In several cases the structures of the photoproducts are determined by 13CO labelling and force-field calculations.