Metal ions in sulfur-rich coordination spheres are of significance due to their
relevance to the active sites of heterogeneous catalysts and metalloenzymes. Of
special interest are the ruthenium-sulfur system, because RuS
2 is known to be an
active catalyst for hydrodesulfurization. In this thesis, ruthenium complexes
containing a sterically bulky arylthiolate ligand will be synthesized and its reactivity
toward small molecules and oxidizing agents will be investigated. Also of interest are
bimetallic iron complexes with bridged-nitrido ligands because of the reports that
nitrido-bridged diiron nitrido phthalocyanine complexes are active catalysts for
oxidation of hydrocarbons. Therefore, in this work efforts have been made to
prepare heterometallic iron(IV) nitrido complexes and explore the iron oxidation
chemistry.
In Chapter 2, the reactivity of the previously reported Ru(II) phosphine thiolate
complex [Ru(PPh
3)
2(STipp)
2] (Tipp = 2,4,6-triisopropylphenyl) has been studied. The
reductions of [Ru(PPh
3)
2(STipp)
2] with CO and NO gave [Ru(CO)
2(PPh
3)(μ-STipp)]
2 and [Ru(PPh
3)
2(NO)
2], respectively. The oxidation of [Ru(PPh
3)
2(STipp)
2] to give
trigonal bipyramidal Ru(IV) thiolate complexes has been studied. Reaction of
[Ru(PPh
3)
2(STipp)
2] with p-tolyl azide (p-tolN
3) led to formation of the Ru(IV)
tetrazene complex [Ru{N
4(p-tol)
2}(STipp)
2(PPh
3)], whereas that with tosyl azide
(TsN
3) yielded the imido complex [Ru(η
2-O,N-NTs)(STipp)
2(PPh
3)]. Treatment of
[Ru(η
2-O,N-NTs)(STipp)
2(PPh
3)] with excess TsN
3 afforded the tetrazene complex
[Ru(N
4Ts
2)(STipp)
2(PPh
3)], confirming that the formation of the Ru(IV) tetrazene
involves the [3+2] addition of Ru=NR with RN
3 (R = p-tolyl or Ts). Oxidation of
[Ru(PPh
3)
2(STipp)
2] with PhICl
2 and l
2 led to formation of [Ru(PPh
3)(STipp)
2Cl
2] and
[Ru(PPh
3)(STipp)
2l
2] respectively. Upon column chromatography on silica,
[Ru(PPh
3)(STipp)
2Cl
2] was hydrolyzed to yield the Ru(IV) hydroxide
[Ru(PPh
3)(STipp)
2(OH)Cl]. [Ru(η
2-N,N'-N
2CPh
2)(STipp)
2(PPh
3)] was synthesized from
the reaction of [Ru(PPh
3)
2(STipp)
2] with Ph
2CN
2.
In order to compare the ligand property of thiolate and selenolate, the
selenium analogue of [Ru(PPh
3)
2(STipp)
2] was synthesized and its oxidation
reactions were studied. In Chapter 3, the synthesis and crystal structure of the
14-electron, 4-coordinate Ru(II) selenolate complex [Ru(PPh
3)
2(SeMes)
2] (Mes
= 2,4,6-trimethylphenyl) was reported. The bonding and structure of
[Ru(ER)
2(PPh
3)
2] (ER = STipp, SeMes) has been analyzed by DFT calculations. The
donor strength of the selenolate and thiolate ligands has been compared. Similar to
[Ru(PPh
3)
2(STipp)
2], [Ru(PPh
3)
2(SeMes)
2] are readily oxidized by organic azides
and diazoalkanes to give imido and diazoalkane complexes, respectively.
Oxidation of [Ru(PPh
3)
2(SeMes)
2] with [Cp
2Fe]PF
6(Cp = η
5-C
5H
5) gave the Ru(IV)
aqua complex [Ru(PPh
3)(H
2O)(SeMes)
3](PF
6) that reacted with phenylacetylene
to yield the acetylide [Ru(PPh
3)(C≡CPh)(SeMes)
3].
Since diiron μ-nitrido phthalocyanine complexes can catalyze the oxidation of
methane, we sought to synthesize heterometallic Fe-N-Ru complexes and elucidate
the effects of the Ru nitride and the macrocyclic ligand on the reactivity of Fe center.
In Chapters 4 and 5, nitrido-bridged heterometallic iron(IV) complexes with
Schiff base and phthalocyanine ligands have been synthesized and their
structure and reactivity have been studied. Treatment of [Fe(salen)(py)
2]
(salen
2- = tetradentate Schiff base ligand) with [L
OEtRu(N)Cl
2) (L
OEt- =
[CpCo{P(O)(OEt)
2}
3]
-) gave [(H
2O)(salen)Fe(μ-N)RuCl(py)(L
OEt)][Cl] that contains a
Fe
IV=N=Ru
IV bridge. Reaction of [Fe(3,5-Br
2sal-o-phen)(py)
2] (3,5-Br
2sal-o-phen =
N,N'-phenylenebis(3,5-dibromosalicylimine) with [L
OEtRu(N)Cl
2] afforded
[Cl(3,5-Br
2sal-o-phen)Fe(μ-N)RuCl(py)(L
OEt)]. Chloride abstraction of
[Cl(3,5-Br
2sal-o-phen)Fe(μ-N)RuCl(py)(L
OEt)] by TIPF
6 gave a Fe(IV)
2-Ru(IV)-Ru(V)
μ-nitrido μ-oxo complex, [{L
OEtRuCl(py)(μ-N)Fe(3,5-Br
2sal-o-phen)}
2(μ-O)[TIPF
6].
Reduction of [Cl(3,5-Br
2sal-o-phen)Fe
IV(μ-N)RuCl(py)(L
OEt)] with CsOH yielded the
Ru(IV)-N-Fe(III) complex [(3,5-Br
2sal-o-phen)Fe
III(μ-N)Ru
IVCl(py)(L
OEt)]. The catalytic
oxidation of styrene and cyclooctene catalyzed with nitrido-bridged Fe(IV) Schiff base
complexes have been studied.
Treatment of [Fe(Pc)] (Pc = phthalocyanine dianion) with [Ru(L
OEt)(N)Cl
2]
afforded the diamagnetic heterometallic complex [Cl
2(L
OEt)Ru(μ-N)Fe(Pc)(H
2O)] that
contains a Ru(IV)=N=Fe(IV) bridge. The oxidations of [Cl
2(L
OEt)Ru(μ-N)Fe(Pc)(H
2O)] with [N(4-BrC
6H
4)
3]SbCl
6 and PhICl
2 gave the phthalocyanine cation radical
complexes [Cl
2L
OEtRu(μ-N)Fe(Pc
⋅⋅+)(H
2O)][SbCl
6]
0.85[SbCl
5(OH)]
0.15 and
[Cl
2L
OEtRu(μ-N)Fe(Pc
·+)Cl], respectively, which have been characterized by UV /visible
and EPR spectroscopy and X-ray crystallography. On the other hand, the oxidation of
[Cl
2(L
OEt)Ru(μ-N)Fe(Pc)(H
2O)] with PhI(CF
3CO
2)
2 led to isolation of [Cl
2L
OEtRu(μ-N)Fe(Pc-OH)(H
2O)](CF
3CO
2) bearing a mono-anionic
hydroxyphthalocyanine ligand, in which the hydroxy group is attached to the inner ring of the Pc macrocycle.
In Chapter 6, the synthesis and structure of Ru nitrido and nitrosyl complexes
supported by thiolate and selenolate ligands are reported.
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