Metal complexes with oxygen donor ligands are of interest because of their relevance to the active sites of oxide-based heterogeneous catalysts. In this thesis, metal complexes with chelating oxygen-donor ligands, including the Kläui tripodal ligand [(η
5-C
5H
5)Co{P(O)(OEt)
2}
3]
- (L
OEt-) and perfluoropincolate [(CF
3)
4C
2O
2]
2- (pin
F), have been synthesized, and their redox and catalytic chemistry has been studied. Also, nitrido-bridged heterometallic iron(IV)/ruthenium(IV) porphyrin complexes have been synthesized and their use as catalysts for alkene epoxidation has been examined. In Chapter 2, Ce(IV) complexes with oxidizing oxyanion ligands have been synthesized and structurally characterized. Reaction of [(L
OEt)
2CeCl
2] with NaIO
4 in water afforded a Ce(IV) periodate complex, 2-2, the crystal of which was found to contain two independent molecules: [(L
OEt)
2Ce(IO
4)
2] (2-2a) and [(L
OEt)
2Ce(H
2O)(IO
4)][IO
4] (2-2b). Treatment of [(L
OEt)
2CeCl
2] with I
2O
5 in CH
3CN in the presence of a trace amount of water led to isolation of the Ce(IV) iodate complex [(L
OEt)
2Ce(IO
3)
2]⋅H
+ICl
2- (2-3). Reaction of [(L
OEt)
2CeCl
2] with K
2S
2O
8 in water afforded the Ce(IV) persulfate complex [(L
OEt)
2Ce(S
2O
8)] (2-4). The cyclic voltammograms of complexes 2-2 – 2-4 in acetonitrile displayed quasi-reversible couples that are attributed to the Ce(III/IV) oxidation. The Ce(IV) periodate and iodate complexes can oxidize methyl p-tolyl sulfide to sulfoxide. A Ru-imidazolin-2-iminato complex has been synthesized by reaction of a Ru(VI) nitride with an N-heterocyclic carbene. Treatment of [L
OEtRu(N)Cl
2] with 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (Im
Dipp) afforded the Ru(IV) imidazolin-2-iminato complex [L
OEtRu(NIm
Dipp)Cl
2] (3-2). Chloride abstraction of 3-2 with TIPF
6 in CH
2Cl
2/MeCN gave [L
OEtRu(NIm
Dipp)(MeCN)Cl][PF
6] (3-3). Oxidation of 3-2 with [(4-BrC
6H
4)
3N][SbCl
6] in CH
2Cl
2 afforded the Ru(V) complex [L
OEtRuCl
3](SbCl
6)⋅(HNIm
Dipp) (3-4). 3-2 and 3-3 exhibited the Ru(V/IV) couples at 0.05 and 0.71 V vs. Fc
+/0 (Fc = ferrocene), respectively. Complexes 3-2 and 3-3 can catalyze the epoxidation of cyclooctene with PhIO, presumably via Ru-oxo intermediates. In Chapter 4, Ru-pin
F complexes have been synthesized and structurally characterized. Treatment of (
nBu
4N)[Ru(N)Cl
4] with Na
2pin
F resulted in the isolation of (
nBu
4N)[Ru(N)(pin
F)Cl
2] (4-1). Reaction of 4-1 with NaL
OEt in MeOH afforded [(L
OEt)Ru(N)(pin
F)] (4-3). Reaction of 4-1 with K[N(Ph
2PQ)
2] (Q = S, Se) afforded [Ru(N)(pin
F){N(Ph
2PQ)
2}] (Q = S (4-5), Se (4-6)). Reaction of 4-3 with PPh
3 and Im
Dipp afforded [(L
OEt)Ru(NX)(pin
F)] (X = PPh
3 (4-7), Im
Dipp (4-8)). Reaction of 4-3 with HBF
4·Et
2O led to isolation of [Ru(N)(pin
F)]
2(μ-OEt)
2 (4-9). Complex 4-1 in conjunction with BF
3 can catalyze the oxidation of cyclohexene, cyclooctene and ethylbezene with tert-butyl hydroperoxide, possibly via an F
3B-N=Ru=O active species. Treatment of [Fe(TPP)Cl] (TPP
2- = tetraphenylpoprhyrin dianion) with sodium naphthanide and [L
OEtRu(N)Cl
2] afforded [(TPP)Fe(μ-N)RuL
OEtCl
2] (5-1) that reacted with 4-tert-butylaniline (L) in CH
2Cl
2 to give [(L)(TPP)Fe(μ-N)RuL
OEtCl
2] (5-2). The crystal structures of 5-1 and 5-2 featuring linear Fe=N=Ru linkages have been determined. Complexes 5-1 and 5-2 can catalyze the oxidation of cyclooctene and cyclohexene with PhIO.
| Date of Award | 2019 |
|---|
| Original language | English |
|---|
| Awarding Institution | - The Hong Kong University of Science and Technology
|
|---|