Abstract
The complexes M(PCy
3)
2(CO)
3 (M = Cr, Mo, W) react with phenyl disulfide to form stable 17-electron radical complexes Ṁ(PCy
3)
2(CO)
3(SPh). Reaction with other alkyl and aryl disuufides also yields stable radicals and reaction with I
2 yields Ẇ(P
1Pr
3)
2(CO)
3(I). Reaction with thiols, hydrogen sulfide and hydrogen iodide yield the corresponding 18-clectron hydrides W(P
1Pr
3)
2(CO)
3(H)(X). The crystal structure of W(P
1Pr
3)
2(CO)
3(H)(I) is reported and allows comparison with the structure of the radical complex Ẇ(P
1Pr
3)
2(CO)
3(I). The WH bond strengths in these heteroatorn complexes are low, 55–57 kcal mol
−1. In spite of steric crowding, H atom transfer from W(P
1Pr
3)
2(CO)
3(H)(SPh) to Ċr(CO)
2(PPh
3)Cp occurs readily due to the stronger nature of the CrH bond formed. The chromium radical does not appear to attack the molecular hydrogen complex W(Pr
3)
2(CO)
3(H
2) or its dihydride form W(Pr
3)
2(CO)n3(H)
2 based on rate of hydrogenation studies. Phenyl disulfide does react with either W(Pr
3)
2(CO)
3(H
2) a its dihydride tautomer W(Pr
3)
2(CO)
3(H)
2 to form thiophenol and W(Pr
3)
2(CO)
3(SPḣ). This reaction is proposed to proceed by reaction of ṠPh radicals which are generated in situ. These studies are used to bracket the first WH bond dissociation energy in W(Pr
3)
2(CO)
3(H)
2. Additional studies of H atom and heteoratom transfer are described.
