Tricarbonyl tungsten oxidation

The electrochemical oxidations of chromium and tungsten tricarbonyl complexes, respectively, were studied. 

There are several classic examples of the use of FTIR spectroelectrochemistry in elucidating the EC reactions of oxidized carbonyl complexes. These include the isomerization of 17e complexes for example, the isomerization of m-[Mo(CO)2(P-P)2]+ to the trans-isomer.139 Similarly, the cis-isomer of [Re(CO)2(P P)2]+ or [Re(CO)(P—P)2X] will isomerize on oxidation as monitored in a reflection IR cell.140 One-electron oxidation of [IrH(CO)(PPh3)3] is reversible, but further oxidation to the dication induces hydride oxidation and the appearance of bands due to the 16e complex [Ir(CO)(PPh3)3]+.141 Oxidation of arene tricarbonyls of Group 6 metals is frequently irreversible, especially in coordinating solvents at ambient temperature. However, the mesitylene tungsten tricarbonyl complex is oxidized by two electrons with the reversible take up of MeCN.142... 

Figure 3-29 Experimental and simulated CVs of the oxidation of 1 mM tricarbonyl-(mesitylene)-tungsten (W) in acetonitrile at 298 K. (Adapted from Reference 14.)...

Reactions.—1-Methyl-3,5-diphenylthiabenzene 1-oxide is a novel sulphur ylide ligand in tricarbonyl-chromium, -molybdenum, and -tungsten complexes (14),... 

Scheme 12.8 Oxidative addition of halogens (CI2, Br2, I2) to molybdenum and tungsten tricarbonyl complexes 19...

Triphosphamacrocycle complexes of molybdenum(II) and tungsten(II) 22 have been prepared by oxidative addition of halogens (CI2, Br2,12) to molybdenum and tungsten tricarbonyl complexes 19 (Scheme 12.8). The metal(O) precursors give rise initially to seven-coordinate salts 21 with a halide anion which may be exchanged for other counter ions. The seven-coordinate complexes 21 are all fluxional in solution. The salts all convert slowly into the neutral seven-coordinate dicarbonyldihalogeno complexes 22 in solution [38]. 

---