REACTION PATHWAYS IN THE REDOX CHEMISTRY OF THE [MO(CO)(2)(DPE)(2)F](+) AND [(MO(CO)(2)(DPE)(2))(2)F](3+) (DPE = PH2P(CH2)(2)PPH2) MO(II) CARBONYL FLUORIDE SYSTEM

Voltammetric oxidation of 0.45 mM [Mo(CO)(2)(dpe)(2)F]PF6 (dpe = Ph2P( CH2)(2)PPh2) in dichloromethane (0.1 M Bu4NPF6) at platinum and glassy carbon macro- and microdisk electrodes gives a one-electron reversibl e couple. Spectroelectrochemical (IR) oxidation studies on the tens of seconds time scale confirm the formation of the first Mo(III) phosphi ne-substituted carbonyl fluoride, [Mo(CO)(2)(dpe)(2)F](2+). However, t he compound is not stable on the longer synthetic (tens of minutes) ti me scale. Bulk electrolytic reduction of [Mo(CO)(2)(dpe)(2)F]PF6 gives cis-Mo(CO)(2)(dpe)(2) and F- quantitatively, but on the voltammetric time scale an intermediate identified as cis-[Mo(CO)(2)(eta(1)-dpe)(et a(2)-dpe)F](-) is detected which then reacts to give cis-Mo(CO)(2)(dpe )(2) and F-. The existence of this and other short-lived intermediates leads to complex cyclic voltammograms which are very concentration, s can rate, and temperature dependent. The fluoride-bridged binuclear co mplex [{Mo(CO)(2)(dpe)(2)}(2)F](PF6)(3) is not oxidized within the pot ential range available, but in reductive cyclic voltammograms it is re duced predominantly to cis-Mo(CO)(2)(dpe)(2), again probably via a flu oride containing intermediate. The reaction 2[Mo(CO)(2)(dpe)(2)F](+) r eversible arrow [{Mo(CO)(2)(dpe)(2)}(2)F](3+) + F- is believed to be i mportant in determining the concentration dependence of the redox beha vior of this Mo(II) carbonyl fluoride system. The electrochemical stud ies reveal that carbonyl fluoride complexes may exist in a wide range of oxidation states and confirm that fluoride is relatively strongly b ound in these types of systems, although in the zero valent reduced fo rm, displacement by a phosphorus ligand does occur.