The effect of the lanthanoid contraction on the nonaaqualanthanoid(III) tris(trifluoromethanesulfonates)

Abstract

The [Ln(H20)9](CF3SO3) 3 complexes with Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Yb and Lu form an isomorphous series of hexagonal structures, a= 13.990(6)-13.259(2), c= 7.444(2)-7.751 (1)A, P63/m, Z = 2. Full crystal data have been published [Harrowfield, Kepert, Patrick & White (1983). Aust. J. Chem. 36,[483][484][485][486][487][488][489][490][491][492]. The [Ln(H20)9] 3+ moiety has a tricapped trigonal prism geometry. The consequences of the lanthanoid contraction were determined from structure refinements with X-ray diffraction intensity data measured for a charge density study at 295 K (wR=0.022-0.051). The Nd structure was also refined with neutron diffraction data (wR = 0.042). The lanthanoid contraction for the bonds to the equatorial oxygens is less than it is for the prism oxygens. This is associated with weakening of the hydrogen-bond network for the equatorial water, while that of the prism water is strengthened. This reflects a change in the interaction between the metal and the ligating water molecules resulting from their orientation. At the upper end of the 4fseries, the trigonally oriented water is less strongly bound.

Aluminum Triflate as a Highly Active and Efficient Nonprotic Cocatalyst in the Palladium‐Catalyzed Methoxycarbonylation Reaction

“…Relative rates were determined for P co (defined as 1 at 25 atm): P co 35 atm = 1.07, P co 45 atm = 1.20, P co 55 atm = 1.25. Additionally, as shown in Table 1 (entries 4-7) and Table 5 (entries [15][16][17][18], rate enhancements were also observed with increasing levels of the Al(OTf) 3 (as was also observed for the Brønsted acids, Table 5), the results of which point to a fractional order dependence on Lewis acid concentration.…”

Highly Hydrated Cations: Deficiency, Mobility, and Coordination of Water in Crystalline Nonahydrated Scandium(III), Yttrium(III), and Lanthanoid(III) Trifluoromethanesulfonates

“…[5] However, from trifluoromethanesulfonate solutions they crystallise with higher hydration numbers in a series of nonahydrated trifluoromethanesulfonate salts, as do the isostructural Group 3 metal ions, scandium(iii), yttrium(iii) and lanthanum(iii). [6][7][8] The isomorphous series of nonaaqualanthanoid(iii) ethylsulfates belongs to the same space group P6 3 /m, [9][10][11] in which the metal ions are located in a crystallographic site that is surrounded by six equidistant water molecules in a trigonal prism with the rectangular sides capped by three more-distant water molecules.…”

Curvature of the lanthanide contraction: An explanation

“…Modern advances in structure analysis have yielded a number of whole or near-whole series of structures for isostructural compounds [4][5][6][7][8], generating much more data for a plot of the lanthanide contraction and showing that the contraction is significantly curved, a feature that we and others in the field have generally accepted.…”

“…The early x-ray and neutron diffraction characterization of the series [Ln(H 2 O) 9 ][CF 3 SO 3 ] 3 was especially significant [6,9], because of its relevance to the solution chemistry of the lanthanide aqua ions. This series is isostructural and the cations have C 3h crystallographic site symmetry.…”

“…2 shows our results for these complexes. Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) [6,8] the cations are also tricapped-trigonal prismatic in geometry. The vertex ionic radii were fixed to a literature value for water [21] and the capping radii were refined, constrained to a single value (the values for Tm, Yb, and Lu are anomalous, which we attribute to steric crowding, and were omitted).…”