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 C_s[Cr(CO)₄(NMe₃)]. The reaction can be reversed by irradiation with λ= 546 nm. At 40 K in Xe isomerization of C_s[Cr(CO)₄(NMe₃)] into C_3v[Cr(CO)₄(NMe₃)] or C_2v[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.