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Synthesis and reactivity of aryl- and alkyl-rhenium(V) imido-triflate compounds: An unusual mechanism for triflate substitution

Organometallics, ISSN: 0276-7333, Vol: 18, Issue: 18, Page: 3715-3727
1999
  • 25
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  • Citations
    25
    • Citation Indexes
      25
  • Captures
    5

Article Description

Treatment of the d rhenium tolylimido complex TpRe(NTol)X with RMgX, RLi, or organozinc reagents yields TpRe(NTol)(R)X [R = Ph, Me, Et, i-Pr, n-Bu; X = Cl or I; Tol = p-tolyl; Tp = hydrotris(1-pyrazolyl)borate] or TpRe(NTol)R (R = Ph, Me). Iodide for triflate metathesis with AgOTf yields TpRe(NTol)(X)OTf[X = Ph, Et, Cl, OTf(=OSOCF)]. Reaction of TpRe(NTol)(Et)I with excess rather than stoichiometric AgOTf generates the ethylene hydride cation [TpRe(NTol)(η-CH)(H)][OTf], which slowly rearranges by ethylene insertion to form TpRe(NTol)(Et)OTf. Treatment of TpRe(NTol)(Ph)I with AgPF gives not iodide abstraction but rather [{TpRe(NTol)(Ph)I}Ag][PF], with two Re-I-Ag linkages. Excess pyridine (py) slowly displaces triflate in TpRe(NTol)Ph(OTf) (11) to give [TpRe(NTol)Ph-(py)][OTf]. The reaction is first-order in 11 and first-order in py. Triflate substitution is similarly slow in the oxo-Tp* derivative, Tp*Re(O)Ph(OTf) [Tp* = HB(3,5-MePz)]. These reactions are many orders of magnitude slower than substitution in the oxo-Tp derivative TpRe(O)Ph(OTf). Kinetic and mechanistic data rule out dissociation of triflate ion in or before the rate-determining step and are most consistent with an associative pathway. Reaction with 1,10-phenanthroline gives the κ-Tp complex [κ-TpRe(NTol)Ph(phen)][OTf], indicating the lability of one arm of the Tp ligand. TpRe(NTol)Ph, TpRe(NTol)Me, TpRe(NTol)(Ph)-OTf, TpRe(NTol)(OTf), [{TpRe(NTol)(Ph)I}Ag][PF], and [κ-TpRe(NTol)Ph(phen)][OTf] have been structurally characterized. The imido ligand is a better electron donor and has a smaller trans influence than an oxo group in this system. © 1999 American Chemical Society.

Bibliographic Details

W. Stephen McNeil; Darin D. DuMez; Yoshihiro Matano; Scott Lovell; James M. Mayer

American Chemical Society (ACS)

Chemistry

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