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 [(η⁵-C₅H₅)Co{P(O)(OEt)₂}₃]^- (L_OEt^-) and perfluoropincolate [(CF₃)₄C₂O₂]^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)₂CeCl₂] with NaIO₄ in water afforded a Ce(IV) periodate complex, 2-...[ Read more ]

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 [(η⁵-C₅H₅)Co{P(O)(OEt)₂}₃]^- (L_OEt^-) and perfluoropincolate [(CF₃)₄C₂O₂]^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)₂CeCl₂] with NaIO₄ in water afforded a Ce(IV) periodate complex, 2-2, the crystal of which was found to contain two independent molecules: [(L_OEt)₂Ce(IO₄)₂] (2-2a) and [(L_OEt)₂Ce(H₂O)(IO₄)][IO₄] (2-2b). Treatment of [(L_OEt)₂CeCl₂] with I₂O₅ in CH₃CN in the presence of a trace amount of water led to isolation of the Ce(IV) iodate complex [(L_OEt)₂Ce(IO₃)₂]⋅H⁺ICl₂^- (2-3). Reaction of [(L_OEt)₂CeCl₂] with K₂S₂O₈ in water afforded the Ce(IV) persulfate complex [(L_OEt)₂Ce(S₂O₈)] (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)Cl₂] with 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (Im^Dipp) afforded the Ru(IV) imidazolin-2-iminato complex [L_OEtRu(NIm^Dipp)Cl₂] (3-2). Chloride abstraction of 3-2 with TIPF₆ in CH₂Cl₂/MeCN gave [L_OEtRu(NIm^Dipp)(MeCN)Cl][PF₆] (3-3). Oxidation of 3-2 with [(4-BrC₆H₄)₃N][SbCl₆] in CH₂Cl₂ afforded the Ru(V) complex [L_OEtRuCl₃](SbCl₆)⋅(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 (ⁿBu₄N)[Ru(N)Cl₄] with Na₂pin^F resulted in the isolation of (ⁿBu₄N)[Ru(N)(pin^F)Cl₂] (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(Ph₂PQ)₂] (Q = S, Se) afforded [Ru(N)(pin^F){N(Ph₂PQ)₂}] (Q = S (4-5), Se (4-6)). Reaction of 4-3 with PPh₃ and Im^Dipp afforded [(L_OEt)Ru(NX)(pin^F)] (X = PPh₃ (4-7), Im^Dipp (4-8)). Reaction of 4-3 with HBF₄·Et₂O led to isolation of [Ru(N)(pin^F)]₂(μ-OEt)₂ (4-9). Complex 4-1 in conjunction with BF₃ can catalyze the oxidation of cyclohexene, cyclooctene and ethylbezene with tert-butyl hydroperoxide, possibly via an F₃B-N=Ru=O active species.

Treatment of [Fe(TPP)Cl] (TPP^2- = tetraphenylpoprhyrin dianion) with sodium naphthanide and [L_OEtRu(N)Cl₂] afforded [(TPP)Fe(μ-N)RuL_OEtCl₂] (5-1) that reacted with 4-tert-butylaniline (L) in CH₂Cl₂ to give [(L)(TPP)Fe(μ-N)RuL_OEtCl₂] (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.