COMPLEXES OF DI- AND TERVALENT COBALT, MONO- AND DIVALENT COPPER WITH 2-(2-ARYLTELLUROETHYL) PYRIDINES: SYNTHESIS AND SPECTRA
Titel:
COMPLEXES OF DI- AND TERVALENT COBALT, MONO- AND DIVALENT COPPER WITH 2-(2-ARYLTELLUROETHYL) PYRIDINES: SYNTHESIS AND SPECTRA
Auteur:
Khalid, Abu Singh, Ajai K.
Verschenen in:
Journal of coordination chemistry
Paginering:
Jaargang 39 (1996) nr. 3-4 pagina's 313-320
Jaar:
1996-11-01
Inhoud:
Complexes of 2-(2-phenyltelluroethyl)pyridine (L1) and 2-{2-(4-methoxyphenyl}telluro) ethylpyridine (L2) with Co(II and III) and Cu(I and II) having compositions [Co(L)Br2] (1, 2), [Co(L)2]BPh4 (3, 4), [Cu(L)Br]2 (5) and [Cu(L)2Br]2(BPh4)2 (6) have been synthesized and characterized by molecular weight, molar conductance, ESR, IR, 1H and 125Te{1H} NMR and electronic spectra in conjunction with magnetic susceptibility measurements and ESCA (in case of Cu (II)). The species 6 is diamagnetic and ESR silent because the odd electron of each copper is paired as two basal coordination planes are coplanar. The μeff values of 1 and 2 (3.5-3.7 BM) indicate the existence of the equilibrium [image omitted] which is supported by molecular weight and ΛM values. The v(Cu-Br) stretch at 181 cm-1 in the IR spectrum of 5 indicates that it is a bromine bridged dimer. The 125Te {1H} NMR signal of L2 undergoes an upfield shift (141 ppm) on coordination with Cu(I). Deshielding of up to 1 ppm of the CH2Te signal in 1H NMR spectra of 3 to 6 indicates that L1/L2 coordinates with Cu/Co via tellurium, a fact which is supported by the deshielding of the 125Te NMR signal (167-200 ppm) on formation of 4 and 6. The pyridine proton ortho to nitrogen also undergoes significant deshielding (0.5 ppm) on formation of 5. Cu(I) species appear to be tetrahedral and Cu(II) ones square planar. Co(II) and Co(III) complexes seem to have octahedral geometry with two bromine atoms in 3 and 4 trans to each other.
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