Transition metal ion initiated chain reactions between tert-butyl hydroperoxide and rhodium hydrides. Rapid hydrogen atom abstraction from rhodium hydrides by methyl radicals

Journal Article · Mon Jul 13 04:00:00 EDT 1998 · Inorganic Chemistry

DOI:https://doi.org/10.1021/ic980089y· OSTI ID:653419

Bakac, A ^[1]

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1. Ames Lab., IA (United States)

In the absence of catalysts, there is no reaction between t-BuOOH and macrocyclic rhodium hydrides LRhH{sup 2+} (L{sup 1} = [14]aneN{sub 4}, L{sup 2} = Me{sub 6}-[14]aneN{sub 4}). The addition of Fe{sub aq}{sup 2+} to such solutions results in rapid and catalytic oxidation of rhodium hydrides (LRhH{sup 2+} + (CH{sub 3}){sub 3}COOH + H{sup +} {yields} LRh{sup 3+} + CH{sub 4} + (CH{sub 3}){sub 2}CO). This reaction occurs by a chain mechanism featuring methyl radicals and LRh{sup 2+} as reactive intermediates. The rates are independent of the absolute concentrations of iron but vary with the ratio of the two oxidation states. The rate constants k{sub obs} are directly proportional to [H{sup +}]. In 0.10 M aqueous HClO{sub 4} at 25 C, the values are 80.8 M{sup {minus}1} s{sup {minus}1} (L{sup 1}RhH{sup 2+}) and 7.0 M{sup {minus}1} s{sup {minus}1} (L{sup 2}RhH{sup 2+}). A macrocyclic cobalt(II) complex, L{sup 2}Co{sup 2+}, is also an effective chain initiator. This reaction is not catalytic in L{sup 2}Co{sup 2+}, which is slowly consumed in the initiation and termination steps. Methyl radicals react rapidly with L{sup 1}RhH{sup 2+} (k = 1.0 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}), L{sup 2}RhH{sup 2+} (1.4 {times} 10{sup 8}), and L{sup 1}Rh{sup 2+} (8.6 {times} 10{sup 8}).

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 653419
• Journal Information: Inorganic Chemistry, Journal Name: Inorganic Chemistry Journal Issue: 14 Vol. 37; ISSN 0020-1669; ISSN INOCAJ
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
COBALT COMPOUNDS
DEHYDROGENATION
EXPERIMENTAL DATA
IRON
OXIDATION
REACTION INTERMEDIATES
RHODIUM HYDRIDES