Sawyer, Jeffery Frederick (1977) Structural studies of secondary and multi-centre bonding in compounds of the non-metals. PhD thesis, University of Warwick.

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Abstract

In this thesis the results of several crystal structure determinations are discussed in terms of their multi-centre inter- and intra-molecular bonding interactions. In Section 1 the structures reported form part of a systematic investigation into the importance of secondary bonding in determining the crystal packing and influencing primary geometry in compounds of the non-metals. In pursuance of this aim, the following crystal structures have been determined: -

(1) The diethyl tin dihalides, Et₂SnX₂ (X = Cl, Br, I).
(2) The solid solvate SeOCl₂-Dioxane and the compound lodoxybenzene.
(3) The compounds iodobenzene diacetate and iodobenzene bis- (dichloroacetate).
(4) cis -3. 5-Dibromo -4-oxo -2, 2,6,6 -tetramethylpiperidin -1 - yloxy, a derived bis nitroxide and (Z, Z)2, 4-Dibromo-1,5- diphen y lpen ta -3 -one.
(5) The novel pseudo polyhalide anion [Me₂N(ICI)₂1ˉas its tetramethylammonium salt.

Each of these structures is discussed in relation to similar examples. In some cases no secondary bonds were found, and possible reasons for this are given. In others, a three-centre overlap of a o* orbital with two lone pairs is proposed as a viable alternative to the principal linear arrangement X-A... Y of primary and secondary bonds found in most examples. A discussion of the significance of these structures in relation to current stereochemical and bonding models, including charge transfer descriptions of the interactions, and possible methods to quantify the strengths of these Interactions are given in Chapter VI.

In Section 2 the topological descriptions of the structures of the boron hydrides and related compounds are discussed in terms of their multi-centre bonding interactions, and the classification of the geometries of the boron polyhedra as closo, nido, arachno and hypho. The hypho class is by far the least well-known, and the crystal structures have been determined of three new examples isoelectronic with the hypothetical hypho B₅H₁₁ ²ˉ, ion. viz.

B₅H₉ . L [L = (Ph₂P)₂CH₂, (Ph₂PCH₂)₂ and (Me₂ NCH₂)₂]

The geometries of these compounds are significantly different, illustrating the diversity possible within such a related series. The structural relationships between these compounds are discussed in terms of the involvement of phosphorus 3d orbitals in the bonding of the phosphine adducts, and the contribution of vacant orbital valence structures to the structure of the tetramethylene diamine adduct.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Crystals, Chemical structure, Chemical bonds
Official Date:	October 1977
Dates:	Date Event October 1977 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Alcock, N. W. (Nathaniel Warren)
Sponsors:	Science Research Council (Great Britain)
Extent:	1 volume (various pagings)
Language:	eng

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