Structural Systematics of Rare Earth Complexes. XI ('Maximally') Hydrated Rare Earth(III) Trifluoro- and Trichloro-acetates

摘要

Room-temperature single-crystal X-ray structure determinations carried out on 'maximally' hydrated rare earth(III) trifluoroacetates, Ln(tfa)_3.xH_2O, crystallized at room temperature, show the Ln = La, Ce adducts to be isomorphous and monoclinic, P2_1/c, a approx= 11.9, b approx= 12.8, c approx= 9.8 A, #beta# approx= 103.7 deg, Z = 4; they are trihydrates. The Ln = Pr, Lu (and, implicitly, intermediate Ln) adducts are also monoclinic, P2_1/c, Z = 4, and trihydrates, but of a different polymorph, with a approx= 9.2, b approx= 18.8, c approx= 9.8 A, #beta# approx= 114 deg. For the four determinations, conventional R values on |F| were 0.038, 0.32, 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 others 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 differ in the number of water molecules (2 cf. 3) ion 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.xH_2O, suggests the following arrays to be prevalent. The Ln = La adduct is a pentahydrate, monoclinic, P2_1/c, a 5.636(7), b 22.454(4), c 16.58(1) A, #beta# 90.52(8) deg, 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, P2_1/c, a 10.071(2), b 22.973(2), c 20.222(5) A, #beta# 119.48(2) deg, 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 be 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 Lu) are dihydrates, triclinic, P1-bar a approx= 11.70, b approx= 12.8, c approx= 15.3 A, #alpha# approx= 71, #beta# approx= 77.85, #gamma# approx= 65.5 deg, 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 new bridges, resulting in a stepped Ln_∞ 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, P1, a approx= 12, b approx= 11.8, c approx= 11.4 A, #alpha# approx= 114, #beta# approx= 100, #gamma# approx= 104 deg, Z = 2 f.u., R 0.056, 0.50 for N_o 3843, 4171. The complexes are centrosymmetric dimers [(EtOH)_3(tca-O)Ln(O-tca-O')_4Ln(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~+) [(H_2O)_2-(tca-O) (tca-0,O')_2La(O-tca-O')_2La(O,O'-tca)_2(O-tca)(OH_2)_2]~(2-), is triclinic, P1-bar, a 13.901(2), b 13.764(3), c 10.073(2) A, #alpha# 104.04(2), #beta# 108.93(2), #gamma# 101.50(2) deg, 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 LaO_9 array are occupied by a pair of O,O'-chelating and one O-unidentate ca