Crystal and Molecular Structures of Some Organometallic Compounds

Woodhouse, David Innes (1974) Crystal and Molecular Structures of Some Organometallic Compounds. PhD thesis, University of Glasgow.

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In Part I of this thesis, I describe some aspects of crystal structure analysis; in particular those methods employed in this research. In Part II, the structural investigation of three organometallic complexes by X-ray diffraction is reported, viz. (N-ethoxycarbonyl-3-formylazepine)tricarbonyliron, pi-cyclopentadienyl-cis-dicarbonylbromo(triphenylphosphine)molybdenum -methylene chloride and pi-cyclopentadienyl-trans-dicarbonyliodo-(phenyl isocyanide)molybdenum. Previous X-ray analyses of azepine-tricarbonyliron complexes have shown that the geometry within the azepine ring is modified by substitution, therefore the structure elucidation of (N-ethoxycarbonyl-3-formylazepine)tricarbonyliron was undertaken in order to examine the geometry in a 1,3-substituted complex. Bond length variations consistent with those in the other complexes have been found. The structure determinations of the molybdenum complexes were undertaken to augment the already considerable structural comparisons possible among complexes of the type (pi-C5H5)MoL2XY. In the analysis of cis-(pi-C5H5)Mo(CO)2(PPh3)Br, halo/carbonyl disorder has prevented the determination of meaningful Mo-CO distances, but sensible values involving the other ligands have been obtained. The interest in the structure of trans-(n-C5H5)Mo(CO)2(CNPh)l was centred on the phenyl isocyanide ligand, for which an almost linear Mo-C-N-C geometry was found, with a Mo - CNPh bond length consistent with the pi-accepting ability of the phenyl isocyanide ligand being nearly comparable with that of the carbonyl ligands. In Part III, the characterization by X-ray analysis of a chromium and three iron organometallic complexes is reported. The analysis of the chromium complex was undertaken to determine whether the monomeric formulation, (pi-C5H5)Cr(NO)(NPh2)l, or a formulation involving weak iodine or nitrogen bridges was correct. The complex was found to be monomeric and structural comparisons have been made with related chromium-cyclopentadienyl-nitrosyl complexes. An X-ray analysis was carried out on the hexafluorophosphate salt of a stable intermediate isolated from the Friedel-Crafts acylation of (hexa-2,4-diene)tricarbonyliron, in order to assert whether the iron atom directs the entering electrophile endo or exo to the organic ligand. The configuration of the cation of the intermediate, tricarbonyl(2-4-n-hepten-5-methyl-6-one)iron, was found to be that resulting from endo-acylation. A product of the photochemical reaction of benzyldicarbonyl-(pi-cyclopentadienyl)iron with triphenylphosphine has been examined by X-ray diffraction and found to be (1-exo-benzylcyclopenta-2,4-diene)- dicarbonyl(triphenylphosphine)iron, in contradiction to the spectroscopic assignment. The tetracyanoethylene adduct of this product has been characterized by a further X-ray analysis as dicarbonyl (pi-cyclopentadienyl)(triphenylphosphine)iron 1,1,2,3,3-penta-cyanopropenide. As a consequence of disorder, accurate dimensions for the anion could not be obtained, but structural comparisons have been possible between the cation, formally a FeII complex, and its closely related precursor, formally a FeO complex. The most notable feature is a longer, ca. 0.03 A, Fe-P bond length in the FeII complex.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1974
Depositing User: Enlighten Team
Unique ID: glathesis:1974-78653
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:06
Last Modified: 30 Jan 2020 15:06

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