Synthesis, properties and multinuclear NMR studies of chelating telluride ligands and complexes
Synthesis, properties and multinuclear NMR studies of chelating telluride ligands and complexes
A convenient synthesis for RTeLi (R = Me, Ph) is described. The RTeLi react with organic dihalides X(CH2)3X (X = Cl, Br), the products depending upon the temperature, the carbon chain length and the halide. Thus at low temperatures the ligands RTe(CH2)nTeR (n = 1,3,6) can be prepared in good yield. When n = 4 or 5 the products are mainly R Te plus Te(CH2)n-1CH2, although small amounts of the ligands n = 5 are seen. Preparations for MeC(CH2TeMe)3 and C(CH2TePh)4 are also described. Unexpectedly the reaction of MeTeLi with C(CH2Br)4 gave CH2CH2C(CH2TeMe)2. The hybrid ligands o-C6H4(TeMe)Y (Y = OMe, SMe, SeMe, TeMe, NMe2, PMe2, AsMe2 and SbMe2) were prepared together with the analogous o-C6H4(SeMe)Y series using a variety of synthetic techniques. These generally involved the utilization of the aryl lithium or grignard reagents already carrying the heteroatom ortho to the site of attack. Notable exceptions included the nucleophilic attack of o-C6H4(SeMe)Br to introduce a new group ortho to the -SeMe (Y = PMe2, AsMe2, SbMe2) and nucleophilic attack of o-C6H4Br2 by MeTeLi to form o-C6H4(OMe)(TeMe) and o-C6H4(TeMe)2 respectively. Characterisation of all these ligands has been achieved using elemental analysis, mass spectrometry and various multinuclear (1H, 13C, 31P, 77Se, 125Te) nmr studies where applicable. A linear relationship has been identified between the 125Te and 77Se nmr chemical shifts of analogous compounds. Stable 5- and 6-membered chelate ring complexes of the bidentate tellurides with Pd(II), Pt(II) and Ir(III) have been prepared. Trends in the 125Te nmr chemical shifts and in 1J(Te-Pt) with invertomer, metal and trans halide have been uncovered and compared with similar trends in 77Se nmr studies. A ring contribution Δ_R has been observed by comprison of the ^125Te chemical shifts with analogous cis-monodentate complexes, effects first observed in the ^31P nmr spectroscopy of chelating phosphines. The complexes Pt[RE(CH_2)_3ER]X_2 (R = Me, Ph; E = S, Se, Te; X = Cl, Br, I) show a dependence of the ^195Pt chemical shift on the donor atom and trans halide, with the terminal (R) groups and their conformation having relatively little influence. All the complexes were characterised by elemental analysis, ir, uv and the appropriate multinuclear nmr spectroscopies. The single crystal X-ray study of Pd[PhTe(CH_2)_3TePh]Br_2 is reported.(DX86223)
University of Southampton
1988
Kemmitt, Timothy
(1988)
Synthesis, properties and multinuclear NMR studies of chelating telluride ligands and complexes.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
A convenient synthesis for RTeLi (R = Me, Ph) is described. The RTeLi react with organic dihalides X(CH2)3X (X = Cl, Br), the products depending upon the temperature, the carbon chain length and the halide. Thus at low temperatures the ligands RTe(CH2)nTeR (n = 1,3,6) can be prepared in good yield. When n = 4 or 5 the products are mainly R Te plus Te(CH2)n-1CH2, although small amounts of the ligands n = 5 are seen. Preparations for MeC(CH2TeMe)3 and C(CH2TePh)4 are also described. Unexpectedly the reaction of MeTeLi with C(CH2Br)4 gave CH2CH2C(CH2TeMe)2. The hybrid ligands o-C6H4(TeMe)Y (Y = OMe, SMe, SeMe, TeMe, NMe2, PMe2, AsMe2 and SbMe2) were prepared together with the analogous o-C6H4(SeMe)Y series using a variety of synthetic techniques. These generally involved the utilization of the aryl lithium or grignard reagents already carrying the heteroatom ortho to the site of attack. Notable exceptions included the nucleophilic attack of o-C6H4(SeMe)Br to introduce a new group ortho to the -SeMe (Y = PMe2, AsMe2, SbMe2) and nucleophilic attack of o-C6H4Br2 by MeTeLi to form o-C6H4(OMe)(TeMe) and o-C6H4(TeMe)2 respectively. Characterisation of all these ligands has been achieved using elemental analysis, mass spectrometry and various multinuclear (1H, 13C, 31P, 77Se, 125Te) nmr studies where applicable. A linear relationship has been identified between the 125Te and 77Se nmr chemical shifts of analogous compounds. Stable 5- and 6-membered chelate ring complexes of the bidentate tellurides with Pd(II), Pt(II) and Ir(III) have been prepared. Trends in the 125Te nmr chemical shifts and in 1J(Te-Pt) with invertomer, metal and trans halide have been uncovered and compared with similar trends in 77Se nmr studies. A ring contribution Δ_R has been observed by comprison of the ^125Te chemical shifts with analogous cis-monodentate complexes, effects first observed in the ^31P nmr spectroscopy of chelating phosphines. The complexes Pt[RE(CH_2)_3ER]X_2 (R = Me, Ph; E = S, Se, Te; X = Cl, Br, I) show a dependence of the ^195Pt chemical shift on the donor atom and trans halide, with the terminal (R) groups and their conformation having relatively little influence. All the complexes were characterised by elemental analysis, ir, uv and the appropriate multinuclear nmr spectroscopies. The single crystal X-ray study of Pd[PhTe(CH_2)_3TePh]Br_2 is reported.(DX86223)
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Published date: 1988
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Local EPrints ID: 460963
URI: http://eprints.soton.ac.uk/id/eprint/460963
PURE UUID: 82d1dbd0-3457-49b5-b289-e6fe9eff531f
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Date deposited: 04 Jul 2022 18:32
Last modified: 04 Jul 2022 18:32
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Author:
Timothy Kemmitt
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