1988 Organometallics 2010, 29, 1988–1991
DOI: 10.1021/om1000502
Reaction of M(II) Diaryls (M = Mn or Fe) with Ammonia to Afford
Parent Amido Complexes
Chengbao Ni, Hao Lei, and Philip P. Power*
Department of Chemistry, University of California, Davis, California 95616
Received January 21, 2010
Summary: The reaction of the two-coordinate diaryls MAr02
catalytic routes.22-24 Currently known metathetical exchange
reactions of NH3 with transition metal organometallic complexes
mainly involve derivatives of the early first-row metals. For
example, group 3-5 metal complexes, such as (η5-Cp*)2ScMe
(Cp* = C5Me5),7 {(η5-Cp)Ti(μ:η1,η5-Cp)}2 (Cp=C5H5),2 (η5-
Cp*)2MH2 (M=Zr or Hf),6 (η5-Cp*)TiMe3,9 and (tBuCH2)3-
TadCHtBu,10 react with NH3 to form bridging amido, imido, or
nitrido complexes with elimination of alkane or H2. NH3 has also
been shown to react with some late second- or third-row transi-
tion metal complexes. For example, the hydride cluster {(η5-
Cp*Ru)3(μ3-H)2(μ-H)3} shows reversible reactivity toward NH3
to form a μ3-imido cluster {(η5-Cp*Ru)3(μ-H)3(μ3-NH)} and
H2.15 Cooperative action of the multiple metal centers in metal
clusters such as {Os3(CO)11(L)} (L=cyclo-C6H8, CH3CN, or
NH3)1,3-5 effectively activates NH3 to form bridging amido
species. Milstein and Hartwig reported the oxidative addition
of NH3 to iridium complexes to afford μ2-NH2 species or
terminal amido/hydride complexes.8,12,14 Furthermore, oxidative
addition reactions of NH3 with low-valent main group metal
species have been reported.16,18,20 The mechanisms and thermo-
dynamics of NH3 reactions with transition metal complexes have
been investigated by spectroscopy13,25-30 and computational
studies.30-41 Nonetheless, little attention has been given to
(M = Mn or Fe; Ar0 = C6H3-2,6-(C6H3-2,6-iPr2)2) with excess
NH3 below room temperature afforded the parent amido com-
plexes {Ar0Mn(μ-NH2)(NH3)}2 (1) and {Ar0Fe(μ-NH2)}2 (2) in
good yields. The reactions were accompanied by elimination of the
arene Ar0H. Both complexes were obtained as dimers in which the
metals are bridged by two NH2 ligands. The complex 1 also
includes an ammonia (NH3) ligand bound to each manganese.
Ammonia complexation did not occur in 2, and the metals
remained three-coordinate. The metal electron configurations
are high-spin and antiferromagnetically coupled.
Cleavage of the N-H bond in ammonia under mild conditions
either by insertion of a transition metal atom or by metathetical
exchange with other ligands is attracting increasing interest1-21
because NH3 is an inexpensive potential precursor for a variety of
amino compounds that may be accessible by transition metal
*Corresponding author. E-mail: pppower@ucdavis.edu.
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