Synthesis and spectroscopic characterisation of [MoO(SR)4]–(R = C6H5, C10H7, 4-CH3C6H4, 4-ClC6H4, 3-ClC6H4, 4-FC6H4, 2,6-Cl2C6H3, or C6F5) complexes and [MoO(SC6F5)4]2–

Abstract

The syntheses of [MoO(SR)₄]^–(R = C₆H₅, C₁₀H₇, 4-CH₃C₆H₄, 4-ClC₆H₄, 3-ClC₆H₄, 4-FC₆H₄, 2,6-Cl₂C₆H₃, or C₆F₅) complexes by several different routes are deported. The u.v.-visible, i.r., Raman, e.s.r. spectroscopic and redox properties of these complexes are detailed. The redox potentials of the Mo^VI–Mo^V and Mo^V–Mo^IV couples correlate with the Hammett function (σ) of the aryl substituent(s); E^P(Mo^VI–Mo^V)= 0.53σ+ 0.53 V (vs. saturated calomel electrode, s.c.e.) and E^p(Mo^V-MO^IV)= 0.52σ– 0.71 V (vs. s.c.e.). The effect of the electron-withdrawing substituent(s) is also clearly seen in the u.v.–visible spectra, less so in the vibrational spectra, and is absent in the e.s.r. spectra. The synthesis of [MoO(SC₆F₅)₄]^2– has been demonstrated and this provides the first spectroscopic comparison of [MoO(SR)₄]^n–(n= 1 or 2) complexes.