Structure and bonding in linear-bridged species: electronic, Raman, and resonance Raman spectra of the trinuclear dinitrogen-bridged complex [{Cl(PMe2Ph)4Re(N2)}2MoCl4]

Abstract

The electronic and vibrational spectra of the complex [{Cl(PMe₂Ph)₄Re(N₂)}₂MoCl₄] have been studied in detail. The Raman spectra have been recorded with a variety of different exciting lines; they were found to be enhanced in the vicinity of the intense absorption bands in the visible region, in particular for the bands at 1 818, 689, and 290 cm^–1 attributed to the ν₁(a_1g),ν(NN), ν₂(a_1g),ν(MN), and ν₅(a_1g),ν(ReCl) fundamentals, respectively. Raman band excitation profiles for many a_1g bands, and approximate force-constant calculations, have been co-ordinated with a proposed molecular orbital scheme for the linear skeleton to provide a coherent picture of the bonding in the complex. The (resonant) electronic bands are assigned to e_g(π)â†�e_u(π) and e_u(π*)â†�e_g(π), ¹A_2uâ†�¹A_1g transitions of the linear chain, on the bases of Raman band depolarisation ratio measurements.