Electronic Structure Across the Periodic Table: Chemistry of the Large in Mass and the Small in Size

Dissertation

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

Michael Kiyoshi Mrozik, B.A.

Graduate Program in Chemistry

The Ohio State University

2011

Dissertation Committee:

Dr. Christopher M. Hadad, Adviser

Dr. Russell M. Pitzer

Dr. Claudia Turro

Dr. Bruce E. Bursten

Dr. Chenglong Li

Copyright by

Michael Kiyoshi Mrozik

2011

Abstract

The results of several investigations are presented in this work. Each project results

from research using applied theoretical simulations and electronic structure programs

to elucidate and understand several difficult and complex problems from the bottom

to the top of the periodic table. Work within each of these projects contain efforts to

understand ground, low-lying (≤ 2eV) or highly excited (≥ 500eV) electronic states.

2+ Reactions involving the thorium analog to ferrocene ([Cp2Th] ) were studied, using relativistic effective core potentials and density functional theory, to explore

∗ IV the accessibility of linear thorocene from Cp2Th Ln complexes. Newly predicted

IV ground-state structures of the form Cp2Th Ln where n = 1-5 are reported, where L

− − − − − − − − − = [F] , [Cl] , [Br] , [I] , H2O, [NH2] , [NCS] , NCMe, [CN] , [CHCH2] , [CH3] ,

CO and pyridine N-oxide. With the exception of the amido complexes, all ground states contain a linear Cp2Th unit. The requirements for forming linear actinocene moieties are discussed in light of current results and existing experimental efforts with uranium metallocene complexes.

The activation of small (C1-C4) alkanes and alkenes by bare and oxo-ligated ac- tinide cations (Th+ through Cm+) has been systematically examined using Fourier transform ion cyclotron resonance mass spectrometry. The reactivity trend identified for the highly reactive early actinide ions, Th+ > Pa+ > U+ > Np+, is interpreted to

ii indicate significant 5f electron participation in organoactinide σ-type bond formation for Pa+. Among the seven studied AnO+ ions, only ThO+, PaO+, and UO+ activated

at least one hydrocarbon, with the reactivity of PaO+ being distinctively high. Elec-

tronic structure calculations for PaO+ show that its ground state is [Pa(5f6d)O]+,

i.e., with one 5f and one 6d nonbonding electrons available on the metal, and all of

its excited states up to 1.8 eV have a 5f orbital occupancy of ≥0.8. The high re-

activity and substantial 5f character of PaO+ indicate participation of 5f electrons

in hydrocarbon bond activation for oxo-ligated Pa+. The results of this work reveal

that 5f electrons play a distinctive role in protactinium chemistry involving σ-type

organometallic bonding.

The lower energy levels of the protactinium (Pa) atom are unusually difficult

to treat theoretically. Pa is located where the 6d and 5f energies cross; simple

calculations consistently put the electron configurations 5f 16d27s2 and 5f 26d17s2 in

the incorrect order. We have used multireference spin-orbit configuration interaction

to compute the energies of these states to determine which additional interactions

need to be included. We also discuss the less common J1j coupling scheme suggested

for these atomic states with applications also to the 5f 16d2 and 5f 26d1 states of Pa2+.

The core-excitation of electrons and formation of valenc