Date of Award

1988

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Leslie G. Butler

Abstract

Solid-state deuterium NMR spectroscopy has been applied to several organometallic complexes. The deuterium quadrupole coupling constants for cis-($\mu$-C$\sp{\rm 2}$H$\sb{\rm 2}$)($\mu$-CO) (FeCp$\sp{\rm d=5}$(CO)$\rbrack\sb{\rm 2}$ (Cp$\sp{\rm d=5}$ = 5% deuteriated cyclopentadienyl), trans-($\mu$-C$\sp{\rm 2}$H$\sb{\rm 2}$) (MnCp$\sp{\rm d=2.7}$(CO)$\sb{\rm 2}$) $\sb{\rm 2}$ (Cp$\sp{\rm d=2.7}$ = 2.7% deuteriated cyclopentadienyl), and trans-($\mu$-C$\sp{\rm 2}$H$\sb{\rm 2}$ (CoCp$\sp{\rm d=5}$(CO)) $\sb{\rm 2}$ were determined by conventional solid-state deuterium NMR spectroscopy. The charges on the methylene bridging site for the three bridging methylene metal dimers were calculated by modeling the difference in deuterium quadrupole coupling constant between the sample and the reference molecule, (9,9-$\sp{\rm 2}$H$\sb{\rm 2}$)fluorene, by the change in occupancy of the carbon 2p orbital perpendicular to the C-$\sp{\rm 2}$H bond and in the plane of the dimetallocyclopropane unit. According to this method, no net negative charge was found for the bridging methylene carbon atom in the iron dimer and slight negative charges of $-$0.07 and $-$0.08 e were found for the manganese and cobalt dimers, respectively, relative to an aliphatic carbon atom. This is the first reported use of solid-state deuterium NMR techniques for the study of the electronic structure in organometallic alkyl complexes. The solid-state motions for the cyclopentadienyl ligand in trans-($\mu$-CO)$\sb{\rm 2}$ (FeCp(CO)) $\sb{\rm 2}$ were investigated by a study of variable temperature deuterium spin lattice relaxation times. The experimental and simulated partially relaxed powder patterns for the cyclopentadienyl rings in trans-($\mu$-CO)$\sb{\rm 2}$ (FeCp$\sp{\rm d}$(CO)) $\sb{\rm 2}$ (Cp$\sp{\rm d}$ ca. 70% deuteriated cyclopentadienyl) were obtained for six temperatures in the range 178-300 K, according to a five-site nearest-neighbor jumps model. The activation energy for the process was determined to be equal to 11.4 (9) kJ/mol. Again, this is the first reported application of solid-state deuterium NMR techniques to study the motional properties of organometallic systems. The X-ray crystal structures for (Co$\sb{\rm 4}$Cp$\sb{\rm 2}$(CO)$\sb{\rm 4}$($\mu$-CO)($\mu$$\sb{\rm 3}$-CO)$\sb{\rm 2}$) and cis-($\mu$-CH$\sb{\rm 2}$)($\mu$-CO) (FeCp(CO)) $\sb{\rm 2}$ were solved and compared to the crystal structures of similar complexes. The preliminary results of a solid-state deuterium NMR spectroscopic study of ($\mu$$\sb{\rm 3}$-C$\sp{\rm 2}$H) (Co(CO)) $\sb{\rm 3}$ and of the ethylene ligand in ($\eta$$\sp{\rm 2}$-C$\sb{\rm 2}$$\sp{\rm 2}$H$\sb{\rm 4}$)MnCp$\sp{\rm d}$(CO)$\sb{\rm 2}$ (Cp$\sp{\rm d}$ = 2.7% deuteriated cyclopentadienyl) are also reported.

Pages

209

DOI

10.31390/gradschool_disstheses.4612

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