Studies of some coordination complexes of osmium and iridium in medium to high oxidation states
Studies of some coordination complexes of osmium and iridium in medium to high oxidation states
Various series of osmium complexes have been prepared and characterised by elemental analysis, i.r. and uv-visible spectroscopies and, where appropriate, 31P n.m.r. spectroscopy. Osmium(IV) trans-[OsL2X4] (L= pyridine(py), SeMe2; X= Cl,Br: L= SbPh3; X= Br), together with the analogous anions trans-[OsL2X4]- (L= AsPh3, SbPh3; X= Cl,Br: L= PEtPh2; X= Cl: L= PEt3, PEt2Ph, PPh3, AsEt3; X= Br) have been so studied as have the related compounds mer-[OsL3X3] (L= PMe3, PEtPh2; X= Cl,Br: L= PMe2Ph, AsMe2Ph; X= Cl: L= PEt2Ph, SbPh3; X= Br) and fac-[OsL3X3] (L= py; X= Cl,Br: L= PMe2Ph, AsMe2Ph; X= Cl). Electrochemical studies of all but the latter two complexes showed reversible Os(III)/(IV) redox couples and the mer-[OsL3X3]+ (L= PMe3, PEt3, PEt2Ph, PEtPh2, AsEt3: X= Cl,Br) and fac-[Os(py)3X3]+ (X= Cl,Br) species were isolated by oxidation of the corresponding osmium(III) compound with nitric acid. The [Os(S[(CH2)3SMe]2)Br3]+ species was also isolated but fac-[OsL3Cl3] (L= PMe2Ph, AsMe2Ph) failed to oxidise. The osmium(II) complexes trans-[OsL4X2] (L= py, PMe3, PMe2Ph, SbPh3; X= Cl,Br) and cis-[Os(PMe2Ph)4X2] (X= Cl,Br) have also been prepared and oxidised to osmium(III). Osmium(IV) species trans-[OsL4X2]2+ (L= PMe3, PMe2Ph; X= Cl,Br) were studied in solution by uv-visible spectroscopy but could not be isolated. No other Os(IV)trans-[OsL4X2]2+ species could be generated. Spectroscopic properties varied systematically within and between all the above series of complexes. The X-ray crystal structures of [PPh4][Os(PEt3)2Cl4] (space group P21/n (no. 14)), fac-[Os(PEt2Ph)3Cl3] (space group P1 (no. 2)) and trans-[Os(PMe3)4Cl2][BF4] (space group Fddd (no. 70)) have been determined, the latter two structures showing substantial steric crowding around the osmium atom. Iridium(IV) anions [NEt4][IrLCl5] (L= PPh3, AsPh3, SbPh3, SMe2, SeMe2) have been prepared from the pyridine analogue and examined spectroscopically and electrochemically, although little variation in properties was seen between individual compounds. Attempts were also made to oxidise mer-[IrL3Cl3] (L= py, PEtPh2, AsMe2Ph, SbPh3, SMe2) and fac-[Ir(PEtPh2)3Cl3] to iridium(IV) but no chemical or electrochemical oxidation to [IrL3Cl3]+ species could be effected.
University of Southampton
Mould, Roy Arthur Stedman
1990
Mould, Roy Arthur Stedman
Mould, Roy Arthur Stedman
(1990)
Studies of some coordination complexes of osmium and iridium in medium to high oxidation states.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Various series of osmium complexes have been prepared and characterised by elemental analysis, i.r. and uv-visible spectroscopies and, where appropriate, 31P n.m.r. spectroscopy. Osmium(IV) trans-[OsL2X4] (L= pyridine(py), SeMe2; X= Cl,Br: L= SbPh3; X= Br), together with the analogous anions trans-[OsL2X4]- (L= AsPh3, SbPh3; X= Cl,Br: L= PEtPh2; X= Cl: L= PEt3, PEt2Ph, PPh3, AsEt3; X= Br) have been so studied as have the related compounds mer-[OsL3X3] (L= PMe3, PEtPh2; X= Cl,Br: L= PMe2Ph, AsMe2Ph; X= Cl: L= PEt2Ph, SbPh3; X= Br) and fac-[OsL3X3] (L= py; X= Cl,Br: L= PMe2Ph, AsMe2Ph; X= Cl). Electrochemical studies of all but the latter two complexes showed reversible Os(III)/(IV) redox couples and the mer-[OsL3X3]+ (L= PMe3, PEt3, PEt2Ph, PEtPh2, AsEt3: X= Cl,Br) and fac-[Os(py)3X3]+ (X= Cl,Br) species were isolated by oxidation of the corresponding osmium(III) compound with nitric acid. The [Os(S[(CH2)3SMe]2)Br3]+ species was also isolated but fac-[OsL3Cl3] (L= PMe2Ph, AsMe2Ph) failed to oxidise. The osmium(II) complexes trans-[OsL4X2] (L= py, PMe3, PMe2Ph, SbPh3; X= Cl,Br) and cis-[Os(PMe2Ph)4X2] (X= Cl,Br) have also been prepared and oxidised to osmium(III). Osmium(IV) species trans-[OsL4X2]2+ (L= PMe3, PMe2Ph; X= Cl,Br) were studied in solution by uv-visible spectroscopy but could not be isolated. No other Os(IV)trans-[OsL4X2]2+ species could be generated. Spectroscopic properties varied systematically within and between all the above series of complexes. The X-ray crystal structures of [PPh4][Os(PEt3)2Cl4] (space group P21/n (no. 14)), fac-[Os(PEt2Ph)3Cl3] (space group P1 (no. 2)) and trans-[Os(PMe3)4Cl2][BF4] (space group Fddd (no. 70)) have been determined, the latter two structures showing substantial steric crowding around the osmium atom. Iridium(IV) anions [NEt4][IrLCl5] (L= PPh3, AsPh3, SbPh3, SMe2, SeMe2) have been prepared from the pyridine analogue and examined spectroscopically and electrochemically, although little variation in properties was seen between individual compounds. Attempts were also made to oxidise mer-[IrL3Cl3] (L= py, PEtPh2, AsMe2Ph, SbPh3, SMe2) and fac-[Ir(PEtPh2)3Cl3] to iridium(IV) but no chemical or electrochemical oxidation to [IrL3Cl3]+ species could be effected.
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Published date: 1990
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Local EPrints ID: 460478
URI: http://eprints.soton.ac.uk/id/eprint/460478
PURE UUID: 943ff557-dba5-4938-b23a-9dbfa276d803
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Date deposited: 04 Jul 2022 18:23
Last modified: 04 Jul 2022 18:23
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Author:
Roy Arthur Stedman Mould
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