Synthesis and reactions of β-diketiminato heavy group 14 metal alkoxides and phosphanides

Tam, Eric Chi Yan (2012) Synthesis and reactions of β-diketiminato heavy group 14 metal alkoxides and phosphanides. Doctoral thesis (PhD), University of Sussex.

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Some low-valent, three-coordinated β-diketiminato heavy group 14 metal complexes
have been synthesised and their reactions examined. Initially, our attention is focused
on several β-diketiminatolead(II) alkoxides. The lead(II) alkoxides show different basic
and nucleophilic reactivities from transition metal analogues. For example, the reaction
between the lead(II) tert-butoxide and methyl iodide proceeds only under forcing
conditions to give the lead(II) iodide and methyl tert-butyl ether. However, facile
reversible carbon dioxide insertion into the lead-oxygen bond is observed.

To investigate the steric effect of the bulky β-diketiminato ligand, compounds with
various aromatic groups attached to nitrogen have been made. When either
[(BDIPh)PbCl] (BDIPh = [HC{C(Me)N(C6H5)}2]−) or [(BDIIPP)PbCl] (BDIIPP =
[HC{C(Me)N(4-iPrC6H4)}2]−) was treated with potassium tert-butoxide, the reactions
gave the unexpected bis[β-diketiminato]lead(II) complexes. However, treatment of
[(BDIDMP)PbCl] (BDIDMP = [HC{C(Me)N(2,6-Me2C6H3)}2]−) with AgOTf led to the
expected β-diketiminatolead(II) triflate. These results suggest that the ortho-substituent
on the N-aryl groups in the β-diketiminato ligand plays an important role in influencing
the formation of bis[β-diketiminato]lead(II) complexes.

A series of β-diketiminato heavy group 14 metal phosphanides was synthesised. The
phosphorus is pyramidally coordinated in the compounds containing diphenyl- or
dicyclohexylphosphanido ligands. In contrast, the geometry at phosphorus is planar in
the germanium(II) and tin(II) bis(trimethylsilyl)phosphanides. The phosphorus in the
lead(II) bis(trimethylsilyl)phosphanide is pyramidally coordinated. The observed
conformations may be explained by the steric congestion from the β-diketiminato ligand and electronic effects in the phosphanido ligand. Reactions of the phosphanido
complexes with one equivalent of elemental chalcogen give phosphinochalcogenoito
complexes. Further reaction with elemental chalcogen gives phosphinodichalcogenoato
complexes. In contrast, treatment of the germanium(II) dicyclohexylphosphanide with
elemental chalcogen leads to the formation of germanium(IV) chalcogenide. The
presence of NMR-active nuclei in these complexes makes possible detailed
spectroscopic analysis.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Chemistry
Subjects: Q Science > QD Chemistry > QD0146 Inorganic chemistry
Depositing User: Library Cataloguing
Date Deposited: 13 Dec 2012 13:25
Last Modified: 08 Sep 2015 12:13

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