Reaction pathways in the redox chemistry of the [Mo(CO)2(dpe)2F]+ and [{Mo(CO)2(dpe)2}2F]3+ (dpe = Ph2P(CH2)2PPh2) Mo(II) carbonyl fluoride system

Alan M. Bond, Ray Colton, David G. Humphrey, Vanda Tedesco, Adrian Van Den Bergen

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Abstract

Voltammetric oxidation of 0.45 mM [Mo(CO)2(dpe)2F]PF6 (dpe = Ph2P(CH2)2PPh2) in dichloromethane (0.1 M Bu4NPF6) at platinum and glassy carbon macro- and microdisk electrodes gives a one-electron reversible couple. Spectroelectrochemical (IR) oxidation studies on the tens of seconds time scale confirm the formation of the first Mo(III) phosphine-substituted carbonyl fluoride, [Mo(CO)2(dpe)2F]2+. However, the compound is not stable on the longer synthetic (tens of minutes) time scale. Bulk electrolytic reduction of [Mo(CO)2-(dpe)2F]PF6 gives cis-Mo(CO)2(dpe)2 and F- quantitatively, but on the voltammetric time scale an intermediate identified as cis-[Mo(CO)21-dpe)(η2-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, scan rate, and temperature dependent. The fluoride-bridged binuclear complex [(Mo(CO)2-(dpe)2}2F](PF6) 3 is not oxidized within the potential range available, but in reductive cyclic voltammograms it is reduced predominantly to cis-Mo(CO)2(dpe)2, again probably via a fluoride containing intermediate. The reaction 2[Mo(CO)2(dpe)2F]+ ⇋ [{Mo(CO)2(dpe)2}2F]3+ + F- is believed to be important in determining the concentration dependence of the redox behavior of this Mo(II) carbonyl fluoride system. The electrochemical studies reveal that carbonyl fluoride complexes may exist in a wide range of oxidation states and confirm that fluoride is relatively strongly bound in these types of systems, although in the zero valent reduced form, displacement by a phosphorus ligand does occur.

Original languageEnglish
Pages (from-to)3908-3915
Number of pages8
JournalOrganometallics
Volume17
Issue number18
Publication statusPublished - 31 Aug 1998

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