This dissertation investigates three topics in the field of multiple-bonded metal chemistry.
The first topic concerns the synthetic and theoretical considerations of ditungsten
formamidinates and guanidinates compounds. This work presents an enhanced synthetic path to
the W2(hpp)4 molecule (Hhpp = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine). The
reflux of W(CO)6 with Hhpp in o-dichlorobenzene at 200 oC produces W2(hpp)4Cl2 in a one-pot
reaction in 92% yield. This compound is stable and easily stored for further use, and it can be
efficiently reduced in a one-step reaction to the most easily ionized compound W2(hpp)4. This
work also examines the electronic structure and geometry of the intermediates W2(õ-CO)2(õ-
hpp)2(÷2-hpp)2 and W2(hpp)4Cl2.
The second topic concerns the theoretical investigation by DFT of the electronic
structure of [Mo2] units bridged by oxamidate ligands or bridging hydride ions ([Mo2] =
(Mo2(DArF)3, where DArF is the anion of a diarylformamidine). It is shown that the effect of the
gauche conformation of the ñ oxamidate isomers is due to steric interactions, and that the planar
ò oxamidate isomers have an electronic structure similar to that of naphthalene when it is doubly
oxidized. The [Mo2](õ-H)2[Mo2] compound shows interdimetal unit interactions between the ô
orbitals of the two [Mo2] units. These interactions are theoretically predicted and experimentally
observed by a decrease in the [Mo2]---[Mo2] distance with a one-electron oxidation of [Mo2](õ-
H)2[Mo2]. The final topic concerns the magnetic and structural properties of two Ru2(DArF)4Cl
compounds. The compounds with Ar = p-anisyl (para) and m-anisyl (meta) both show different
temperature dependence of their molar magnetic susceptibility, ÃÂ. For the para compound, there
is a Boltzmann distribution between a ÃÂ*3 ground state and a ô*2ÃÂ* upper state, and this is
confirmed by a temperature dependence of the Ru-Ru bond length: 2.4471(5) ÃÂ
at 23 K and
2.3968(5) ÃÂ
at 300 K. For the meta compound, a ô*2ÃÂ*configuration persists over the range of
23-300 K as shown by an invariant Ru-Ru bond length and its molar magnetic susceptibility.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4722 |
| Date | 25 April 2007 |
| Creators | Villagran Martinez, Dino |
| Contributors | Cotton, F. Albert |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 2648068 bytes, electronic, application/pdf, born digital |
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