Baird, Donald M.

Molecular architecture has been used to develop new materials with our knowledge of Bis(arylimino)isoindoline (BAII). Ni(BAII)2,\ Ni(NBAII)2 and Cu(NBAII)(OAc) complexes were prepared and studied using their Crystal packing diagrams and data in order to evaluate $\pi$-overlapping. It is believed that $\pi$-overlapping will occur in complexes with mono BAII substituted complexes and not di-substituted. The first steps have been made in the development of a polymeric BAII complex with the production of an oligomeric BAII (GBAII). The GBAII complex was analysis using a molecular device approach with the use of NMR instrumentation.

The presence of multiply bonded dimetal units in materials offers opportunities for tuning properties of solids. Materials containing molybdenum-molybdenum quadruple bonds have recently begun being reported. This thesis reports the products of the reactions of dimethyl sulfide (DMS), acetonitrile (ACN) and acetate complexes, Mo2CI4(DMS)4, Mo2(ACN)10ABF4, and Mo2(0Ac)4
with 2,2';6,2"-terpyridine, 4'-phenyl 2,2';6,2"-terpyridine, 2,3,5,6-tetrakis (alpha-pyridyl) pyrazine and 1,3-bis(4-methylimino)isoindoline. Among these ligands, 2,3,5,6-tetrakis (alpha-pyridyl) pyrazine may lead to linear arrays of metal-metal bonds as well as other ordered structures. 1H-NMR, electronic absorption, and infrared data will be quoted to support any structural assignments.

Mo2O3(Et2dtc)2(THF) 2I2 (1) reacts with a variety of oxygen atom donor substrates, X-O, such as pyridine-N-oxides, sulfoxides and nitrate to produce MoO2^2+ complexes and X by oxygen atom transfer. Results from kinetics studies indicate the formation of a (1)-substrate intermediate that decomposes to form the products. The lifetime of the intermediate apparently depends on the stability of the leaving group, X. Since the R-group in nitroso compounds, R-N=0, would not be stable leaving groups the (1)-nitroso complex might be expected to be quite long lived or even stable. Indeed, reaction of (1) with nitroso compounds such as nitrosobenzene produce stable molybdenum-oxaziridines which have been identified using 1H-NMR, IR and electronic spectral data. The use of these complexes in the mediation of allylic amination reactions was studied.

Transition metal complexes of the mononucleating 1,3-bis(pyridylimino)isoindoline ligand (BAII) have been useful as redox catalysts and as models for naturally occurring metal centers. The redox properties of binuclear 1,3,5,7-tetra(pyridylimino)benzodipyrrole (TAII) complexes have also been investigated. Attempts to prepare 1,3,6,8-tetra(2-(4-methylpyridyl)imino)naphthodipyrrole (NTAII) using calcium chloride catalysis and solid fusion will be discussed. Divalent Cu, Ni, Zn, and Pd complexes of the mononucleating 1,3-bis(pyridylimino)benz(f)isoindoline ligand (NBAII) were prepared and the crystal structure of Cu(II)OAc(NBAII) is discussed. It is believed that the dimolybdenum NBAII complex has also been prepared. The NBAII complexes were characterized using NMR, IR, and UV-visible spectroscopy.

The planar, dinuclear, tridentate ligands, 1,3,5,7-tetrakis(2-pyridylimino)benzodipyrrole (TAII) and 1,3,5,7-tetrakis(4,6-dimethyl-2-pyridylimino)benzodipyrrole (DiMeTAII) were synthesized and characterized as were all intermediates characterized by both infrared and 1H-NMR spectra. Evidence is presented for the formation of Mo4(OAc)6-(DiMeTAII) (I), the dinuclear analog of Mo2(OAc)3-BAII using UV/Vis to show the delta--->delta* transition typical of the quadruple bond and for the determination of percent molybdenum which is consistent with the proposed structure. A review of recent studies into the field of quadruply bonded metal containing polymers will be discussed along with application of compound (I) in this field.

A study of the kinetic behavior of the oxygen atom transfer reaction of Mo2o3 (Et2dtc)2 (THF) 2I2, (I), with a variety of derivatives of pyridine N-oxides has been performed. The reaction behaves in pseudo-first-order fashion under conditions of excess N-oxide. Plots of kobs vs. [N-oxide] do not give straight lines, while plots of 1/kobs vs. 1/[N-oxide] are linear. The rate constant k is taken as the inverse of the slope of this latter plot. There is a marked dependence of the rate on the functional group in the 4-position of the pyridine ring with the relative rates -CH3 > -H > -Cl > -CN. The above observations can be used to support a mechanism in which a rapid pre-equilibrium, with a large equilibrium constant, is followed by a rate-determining breaking of the Mo-O-Mo bridge.

The complexes MoX4(Multiimine)2, where X = Cl, Br, I and Multiimine = dimethyl-bipyridine, bipyridine, phenanthroline, bipyrazine, bipyridazine and bipyrimidine, have been prepared. The product complexes apparently contain non-bridged quadruple molybdenum-molybdenum bonds. Each molybdenum is coordinated to a bidentate diimine and two halogen atoms. An electronic absorption study reveals an important trend that the intensity of the delta-->delta* transition increases with decreasing energy. This shows the energy of this band is determined by mixing of this transition with a metal-to-ligand charge transfer transition. An EEC type mechanism is proposed for the redox behavior of these compounds on the basis of an electrochemical study and some consistent results are obtained by correlating the oxidation potentials with the delta-->delta* transition energies. Also, fairly good correlations of both the delta-->delta* transition energies and the oxidation potentials with pk(a) of L are obtained.

Mo2o3 (Et2dtc) 2 (THF) 2I2, readily reduces various oxides. The Mo vio2+2 product of this reaction oxidizes TPP to triphenylphosphine oxide. The transient Mo(iv) species formed in the later reaction rapidly and irreversibly reacts with excess Mo vio2+2 to form the original Mo2 o3 4+ complex. These reactions can be also be coupled to provide catalytic oxygen transfer from PNO to TPP. This catalytic cycle can be monitored using a reverse phase high pressure liquid chromatography method that will also be discussed. The oxides chosen ranged from pyridine-N-oxide to the biological substrates: diphenylsufoxide, DMSO, nicotinamide-N-oxide, and biotin-S-oxide. Since Mo2o3 (Et2dtc) 2 (THF) 2I2 has the ability to abstract oxygen from these biologically significant substrates, it may result in the reconsideration of the role of Mo(V) complexes in catalytic cycles.

The complexes Mo2(OAc)3(BAII), where BAII is 1,3-bis(arylimino)isoindoline, have been synthesized. A detailed interpretation of their 1H-NMR spectra has been made. The structure of the bis(pyridylimino)isoindoline derivative has been determined by X-ray analysis to facilitate the assignment of the resonance lines in the spectra. It has been found that there are trends in energies and intensities of the delta-->delta* transition in these compounds. Electron withdrawing substituents on the aromatic nitrogen heterocycles in BAII shift the delta-->delta* transition to a lower energy and a higher intensity as compared to electron releasing substituents. These trends suggest that mixing of M-->L charge transfer transitions with the delta-->delta* transitions is occurring in these compounds which is consistent with the results of electrochemical trends in oxidation potentials. The complexes which are hardest to oxidize in general have the lowest delta-->delta* transition.

A new polymeric ligand, poly[5-(1,3-bis-(2'-pyridylimino) isoindolyloxy)ethylene], was synthesized. At same time, 1,3-bis-(2 '-pyridylimino)-5-hexadecanyloxyisoindoline was also synthesized. These two products were characterized with fourier transform infrared spectrometry, ultraviolet spectrometry, mass spectral analysis and elemental analysis. Their complexes of Cu+2 were prepared.