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Ternary Lanthanide Complexes of the Type [M(HMPA) 4 (NO 3 ) 3 ]: A new method of synthesis and spectroscopic studies including a comparison of the electronic spectra of the [M(HMPA) x (ClO 4 ) 3 ] complexes

1977; Wiley; Volume: 434; Issue: 1 Linguagem: Inglês

10.1002/zaac.19774340134

1521-3749

Shyama P. Sinha,

Crystal structures of chemical compounds

Abstract The ternary complexes of the composition [M(HMPA) 4 (NO 3 ) 3 ], where M = trivalent lanthanides and yttrium, and HMPA = hexamethylphosphoramide, have been synthesized by a special liquid‐liquid extraction technique. The infrared and Raman polarization data confirmed that all ligands are coordinated to the central metal ion and that the nitrate groups are behaving as bidentate ligands, thus giving the central ion a coordination number of ten. From the f → f transitions in the electronic spectra of [M(HMPA) 4 (NO 3 ) 3 ] (I), [M(HMPA) 4 (ClO 4 ) 3 ] (II) and [M(HMPA) 6 (ClO 4 ) 3 ] (III) complexes, Sinha's covalency parameters have been evaluated, which show the following general trend III < II < I and support the conclusions drawn from the vibronic spectra of these complexes. Preliminary investigation of the proton n.m.r. spectra of the nitrate complexes has shown that in CDCl 3 solution around 35°C the ligand exchange for the havier lanthanides is slower than that for the ligther ones, thus giving rise to both coordinated and free HMPA resonances for the Tb(III) and Tm(III) complexes.