Structural systematics of rare earth complexes. XI . ('Maximally') hydrated rare earth(III) trifluoro- and trichloro-acetates

P.C. Junk, C.J. Kepert, LU Wei-Min, Brian Skelton, Allan White

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Abstract

Room-temperature single-crystal X-ray structure determinations carried out on 'maximally' hydrated rare earth(III) trifluoroacetates, Ln(tfa)(3).x H2O, crystallized at room temperature, show the Ln = La, Ce adducts to be isomorphous and monoclinic, P 2(1)/c, a approximate to 11.9, b approximate to 12.8, c approximate to 9.8 Angstrom, beta approximate to 103.7 degrees, Z = 4; they are trihydrates. The Ln = Pr, Lu (and, implicitly, intermediate Ln) adducts are also monoclinic, P 21/c, Z = 4, and trihydrates, but of a different polymorph, with a approximate to 9.2, b approximate to 18.8, c approximate to 9.8 Angstrom, beta approximate to 114 degrees. For the four determinations, conventional R values on \F\ were 0.038, 0.032, 0.036, and 0.034 for N-o 2952, 4821, 4544, and 4092 independent 'observed' (I > 3 sigma(I)) diffractometer reflections respectively. The Ln = La, Ce adducts are two-dimensional polymers, the sheets parallel to the bc plane; the other systems are binuclear, the two metal atoms being linked by four bridging carboxylate O-tfa-O' ligands. In both structural types, the metal atoms are eight-coordinate, but direr in the number of water molecules (2 cf. 3) in the O-8 array.Extension of previous studies by single-crystal X-ray methods on the structural characterization of trivalent rare earth trichloroacetates, 'maximally' hydrated at local ambience, Ln(tca)3.x H2O, suggests the following arrays to be prevalent. The Ln = La adduct is a pentahydrate, monoclinic, P 21/c, a 5.636(7), b 22.454(4), c 16.58(1) Angstrom, beta 90.52(8)degrees, Z = 4 f.u., R 0.035 for N-o 4154. The compound is a linear polymer along a, successive nine-coordinate La (separated by a) being linked by three O-tca-O' bridging ligands at the opposite faces of a tricapped trigonal prismatic array, the equatorial sites being filled by water molecules. The Ln = Ce adduct is a trihydrate, monoclinic, P 21/c, a 10.071(2), b 22.973(2), c 20.222(5) Angstrom, beta 119.48(2)degrees, Z = 8 f.u., R 0.050 for N-o 5019. The array is also linear polymeric, but with successive Ce being linked alternately now by sets of two and then four O-tca-O' bridging carboxylates along b, the Ln = Ce coordination number being diminished (relative to La) to eight with the coordination of two water molecules to each metal. Ln = Pr, Lu (and, presumptively, intermediate Ln) are dihydrates, triclinic, , a approximate to 11.70, b approximate to 12.8, c approximate to 15.3 Angstrom, alpha approximate to 71, beta approximate to 77.85, gamma approximate to 65.5 degrees, Z = 4 f.u., R 0.056, 0.059 for N-o 5650, 5398. The array is a linear polymer, similar to that of the Ln = Ce adduct but alongside the bridging acetate pair one of the water molecules now bridges, resulting in a stepped Ln 1 array (along c) rather than a quasi-straight one as is found for the Ln = Ce (and La) adduct.Structure determinations are also recorded for rare earth(III) trichloroacetate ethanol trisolvates, Ln(tca)(3).3EtOH. Adducts of Ln = La, Yb (and, implicitly, intermediate Ln) are isomorphous, triclinic, , a approximate to 12, b approximate to 11.8, c approximate to 11.4 Angstrom, alpha approximate to 114, beta approximate to 100, gamma approximate to 104 degrees, Z = 2 f.u., R 0.056, 0.050 for N-o 3843, 4171. The complexes are centrosymmetric dimers [(EtOH)(3)(tca-O)Ln(O-tca-O')(4)Ln(O-tca)(HOEt)(3)], the two metal atoms being linked by four O-tca-O' bridging carboxylate groups; the metal atoms are eight-coordinate, the other four sites being occupied by four oxygen atoms from unidentate ethanol and carboxylate moieties.Bis(bis(2-pyridyl)aminium) bis(diaquatetrakis(trichloroacetato)lanthanate(III)), 2(dpaH(+)) [(H2O)(2)(tca-O)(tca-O,O' )(2)La(O-tca-O')(2)La(O,O'-tca)(2)(O-tca)(OH2)(2)](2-), is triclinic, , a, 13.901(2), b 13.764(3), c 10.073(2) Angstrom, alpha 104.04(2), beta 108.93(2), gamma 101.50(2)degrees, Z = 1 binuclear f.u., R 0.045 for N-o 4999. The anion is binuclear, the two nine-coordinate lanthanum atoms being linked by a pair of bridging O-carboxylate-O' groups. The other seven sites of the LaO9 array are occupied by a pair of O,O'-chelating and one O-unidentate carboxylate groups and a pair of water molecules.
Original languageEnglish
Pages (from-to)459-479
JournalAustralian Journal of Chemistry
Volume52
Issue numberN/A
Publication statusPublished - 1999

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