Voltammetric experiments are reported which establish kinetic and thermodynamic properties associated with the redox chemistry of carbonyl hydride complexes [M(CO)2(P-P)2H](SO3CF3) (M = Cr, Mo, W; P-P = Ph2-PCH2PPh2 (dpm), Ph2PCH2CH2PPh2 (dpe)). A systematic relationship is shown between redox data obtained for the hydride complexes and those for the M(CO)2(P-P)2 complexes. Isomerization reactions of the seven-coordinate hydride complexes give rise to interesting mechanistic features which accompany the oxidation as well as the reduction, and both are found to proceed via metal-hydrogen bond cleavage. The oxidation process corresponds to an ECEC reaction pathway {(E) [Mo(CO)2(dpe)2H]+ = [Mo(CO)2(dpe)2H]2+ + e; (C) [Mo(CO)2(dpe)2H]2+ ⇄ trans-[Mo(CO)2(dpe)2]+ + H+; (E) trans-[Mo(CO)2(dpe)2]+ ⇄ trans-[Mo(CO)2(dpe)2]2+ + e; (C) trans-[Mo(CO)2(dpe)2]2+ → products} or a related mechanism while the reduction process involves the formation of hydrogen: [Mo(CO)2(dpe)2H]+ + e ⇄ cis-Mo(CO)2(dpe)2 + 1/2H2. In the case of the oxidation of the tungsten and the the [Mo(CO)2(dpe)2H]+ complexes, a chemically reversible one-electron oxidation process is detected at low temperature in butyronitrile. The investigation of the deuterated complex [Mo(CO)2(dpe)2D]+ allows the detection of a normal isotope effect on the metal-hydrogen bond cleavage reaction. The oxidized species [M(CO)2-(P-P)2H]2+ can be viewed as extremely strong acids.

Original languageEnglish
Pages (from-to)1705-1710
Number of pages6
JournalInorganic Chemistry
Issue number7
Publication statusPublished - 1 Mar 1995

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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