Oxo and imido/imido exchange and C-H activation reactions based on pentamethylcylopentadienyl imido tantalum complexes
Identifiers
Permanent link (URI): http://hdl.handle.net/10017/4209DOI: 10.1016/S0022-328X(99)00593-8
ISSN: 0022-328X
Publisher
Elsevier
Date
2000Funders
The authors acknowledge DGICYT (project PB97-0776) for financial support and J.S.N. acknowledges MEC for a fellowship.
Bibliographic citation
Journal of Organometallic Chemistry, 2000, v. 597, p. 61-68
Keywords
Oxo/imido imido/imido exchange
C-H activation
Cyclopentadienyl imido tantalum complexes
Project
PB97-0776 (Ministerio de Educación y Cultura)
Document type
info:eu-repo/semantics/article
Version
info:eu-repo/semantics/publishedVersion
Publisher's version
http://dx.doi.org/10.1016/S0022-328X(99)00593-8Rights
(c) Elsevier, 2000
Access rights
info:eu-repo/semantics/openAccess
Abstract
Reactions of [TaCp*Cl4] with two, three and four equivalents of LiNHt
Bu give the halo- and amido-imido complexes
[TaCp*Cl2(Nt
Bu)] (1a), [TaCp*Cl(Nt
Bu)(NHt
Bu)] (2) and [TaCp*(Nt
Bu)(NHt
Bu)2] (3), respectively. The related complex
[TaCp*Cl2{N(2,6-Me2C6H3)}] (1b) is prepared by a similar reaction using two equivalents of Li[NH(2,6-Me2C6H3)]. Complex 3
can be transformed into 2 and further into 1a by reaction with SiClMe3. Complex 1a reacts with CNt
Bu to give the 18-electron
adduct [TaCp*Cl2(Nt
Bu)(CNt
Bu)] (4) whereas addition of excess CN(2,6-Me2C6H3) results in reductive elimination of the
carbodiimide t
BuN C N(2,6-Me2C6H3) (5) to give [TaCp*Cl2{CN(2,6-Me2C6H3)}3]. However complex 1b does not react with any
of the isocyanide ligands. Both complexes 1a and 1b react with PhCHO undergoing imido/oxo exchange to give the imines
PhCH NR (R=t
Bu, 2,6-Me2C6H3 (6)) and dimeric [TaCp*Cl2(O)]2 or trimeric [(TaCp*Cl)3(m2-Cl)(m2-O)3(m3-O)] oxo-complexes,
whereas only 1a reacts with CO2, PhCH NR% (R%=Ph, Me) and (2,6-Me2C6H3)N C Nt
Bu producing t
BuN CO, PhCH Nt
Bu
and t
BuN C Nt
Bu, respectively and the corresponding oxo or imido tantalum derivative. None of the complexes reacts with
CO or NCR (R=Me, Ph). The complex [TaCp*Me(Nt
Bu)(NHt
Bu)] activates C–H bonds when heated in benzene and toluene
affording [TaCp*Ph(Nt
Bu)(NHt
Bu)] (7) and a mixture of [TaCp*(m-MeC6H4)(Nt
Bu)(NHt
Bu)] 8a and [TaCp*(pMeC6H4)(Nt
Bu)(NHt
Bu)] (8b). All of the reported organic compounds and tantalum complexes were characterized by 1
H- and 13C-NMR spectroscopy
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