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Title: Studies in the high oxidation state coordination chemistry of osmium and iron
Author: Harbron, Stephen Kenneth
ISNI:       0000 0001 3531 2424
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 1988
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Six-coordinate trans-dioxoosmium complexes [OsO₂(L-L)X₂](for example, L-L= various diphosphines, diamines, dithioethers, diselenoethers, diamines and some mixed group Vb and BIb species, X= Cl, Br) have been obtained by the reaction between OsO₄ and EtoH/c.HX in varying yields. The complexes [OsO₂(EMe)₂X₂] (E= S, Se4;X= Cl, Br) have also been prepared by a similar route. The materials have all been obtained as tan-brown powders which to varying degrees are subject to photochemical and thermal decomposition. They all exhibit a strong band in the infrared spectrum (ca840cm⁻¹) characteristic of the trans-[OsO₂]2+ group. The thio- and seleno-ether complexes are rare examples of complexes with these ligands in such high formal oxidation states. The bis(diphosphine) complexes trans- [OsO₂(L-L)₂X₂](L-L= o-C₆H₄(PMe₂)₂;X= Cl, Br) have also been prepared although no other examples could be made. Attempts to grow crystals of any of the trans-dioxoosmium(VI) species resulted in powders or oils being deposited in all but one case. The structure of this showed it to be a minor by-product [Me₂NHCH₂CH₂NHMe₂]. [OsO₂Cl₄] exhibiting hydrogen bonding. Several osmium (VI) and osmium (VIII) complexes were made and examined by 17O n.m.r. Osmium (IV) complexes [Os(L-L)₂X₂][C10₄]₂ species have been prepared (L-L= various phosphine and arsine ligands) by oxidation of osmium (III) analogues using nitric acid. The complexes were isolated where possible by centrifugation and removal of the supernatent liquid. They were found to be unstable at room temperature and prone to reduction in moist environments. Osmium (IV) complexes [Os(L-L)X₄](L-L= bidentate phosphine, arsine, stibine; X= Cl, Br) were prepared by adding the ligand to a solution of Na₂OsX₆(X= Cl, Br). Solids were subsequently isolated as green-brown powders and compared with the known thio-ether analogues. None of the osmium (IV) complexes could be induced to give crystals of suitable quality for an X-ray examination. Iron (IV) complexes [Fe(L-L)₂X₂] [BF₄]₂ have been synthesised using HNO₃/HBF₄ as oxidant on the D2h iron (III) analogues and examined by cyclic voltammetry. Some high oxidation state complexes with group Vb and VIb mixed bidentate ligands have been prepared with Ni(III), Pd(IV) and Pt(IV). The nickel species have been examined by e.p.r. All of the complexes made in this study were variously characterised by elemental analysis, electrochemistry, infrared, electronic, nuclear magnetic resonance and electron paramagnetic resonance spectroscopies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: High oxidation state compounds