Date of Award

1-1-1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

The donor properties of Metal acetylacetonates (M(acac)$\sb{\rm n}$) towards a variety of electron acceptors have been investigated. Thermodynamic parameters for the 1:1 Charge-Transfer (CT) complexes between M(acac)$\sb{\rm n}$ and I$\sb2$ have been determined from the blue-shifted I$\sb2$ peaks $(\sim$360 nm) in the UV-Vis. spectra. Positive $\rm\Delta S\sp{o}$ observed for the Zr(IV) and Sc(III) cases suggests that the Zr and Sc acac donors are more solvated in their free state than in the complexed form.The equilibrium constants K$\sb{\rm AD}$ for the M(acac)$\sb{\rm n}$/I$\sb2$ complexes are very different from the values previously reported by other workers. The I-I stretching modes are observed in the far-IR at 140, 139, 138 and 125 cm$\sp{-1}$ for the Al, Sc, Zr and Th complexes, respectively. The positions of these peaks suggest that significant charge transfer occurs from the M(acac)$\sb{\rm n}$ donors to I$\sb2$. This agrees with the observed equilibrium and thermodynamic constants, as well as the large blue shift of the I$\sb2$ $\sigma$-$\sigma$* transition and the position of the CT peaks in the UV.$\sp1$H and $\sp{13}$C NMR studies show no significant change in the chemical shifts of the protons or carbons on the acac ring upon reaction with I$\sb2$. Likewise, $\sp1$H NMR studies of the Al(acac)$\sb3$/phenol system in CCl$\sb4$ show no significant shifts in the phenol ring protons, while the OH proton is shifted downfield from its position in the uncomplexed phenol. This is consistent with hydrogen bonding to the oxygen lone-pair on the acac ring.$\sp1$H NMR studies also show that M(acac)$\sb{\rm n}$ undergo an Aromatic Solvent Induced Shift (ASIS) effect when the solvent is changed from CCl$\sb4$ to benzene. This ASIS effect does not parallel the dipole moments reported for these compounds.Attempts to make CT complexes between M(acac)$\sb{\rm n}$ and NO$\sb2$- or CN-benzene derivatives did not show the expected $\pi$-$\pi$* type of interaction. In cases where there was some kind of interaction, the reaction was too slow to be of CT type. The tris-acac of Al and Co reacted readily with 1,3,5-trinitrobenzene in the highly polar acetone solvent to yield blood-red solutions. (Abstract shortened with permission of author.)

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