Chemistry of molybdenum. Part 5. Synthesis, spectroscopic and electrochemical properties of bis(2-aminocyclopent-1 -ene-1- dithiocarboxylato)(arylimido)dihalogenomolybdenum(VI) complexes

Abstract

The preparation of a series of arylimido complexes [Mo(NC₆H₄X-p)Y₂(acda)₂](Hacda = 2 aminocyclopent-1-ene-1 -dithiocarboxylic acid; X = H, Y = F, Cl or Br; X = Cl or NO₂, Y = Cl) by O/NPh exchange reaction is reported. A novel synthetic route for the generation of arylimido-molybdenum compounds via an oxaziridine precursor has been explored. In [Mo( NPh)Y₂(acda)₂] complexes, a systematic shift of the ligand-to-metal charge-transfer band [S(π)→Mo(dπ)] to higher energy occurs as the ligand field strength of Y increases. Electrochemical studies (cyclic voltammetry) of these compounds in dimethylformamide reveal the presence of a quasi-Nernstian couple (E_½ca.–0.12 to –0.21 V) due to Mo^VI–Mo^V electron transfer followed by a Mo^V–Mo^IV irreversible reduction process (E_p,cca.–0.4 V). It is concluded that the imido group is a poor σ-donor ligand compared to the isoelectronic oxo group.