The Reduction of Rare‐Earth Metal Halides with Unlike Metals – Wöhler's Metallothermic Reduction

Abstract

Rare‐earth halides may be reduced by rare‐earth metals (conproportionation) and, as an alternative, by unlike metals such as alkali or alkaline‐earth metals, a route first established for the production of rare‐earth metals. It has great power for exploratory research subject to enhanced reactivity at lower temperatures and the formation of alkali halide flux for crystal growth. A large number of new compounds, ternary and higher, salt‐like and (semi‐)metallic including interstitially stabilized cluster compounds has been synthesized and characterized during the last decades.

Ru11Lu20, a New Intermetallic Compound with Eight- to Ten-Coordinate Ruthenium Atoms

“…The phase that comes closest is Ru 3 Lu 5 , with 37.5 mol% Ru, as compared with 35.48 mol% in {Ru 11 Lu 20 }. "Ru 3 Lu 5 " melts incongruently at 1460 °C: As crystallographic data are not reported it seems likely that "Ru 3 Lu 5 " = "Ru 12 Lu 20 " is in fact {Ru 11 Lu 20 }.…”

“…The crystal structure of {Ru 11 Lu 20 } exhibits a large unit cell, space group R-3, in the hexagonal setting with a = 1255.1(1), c = 2973.0(4) pm, with six formula units in the unit cell, hence with the composition Ru 66 Lu 120 . There are five crystallographically independent ruthenium sites in the unit cell, Wyckoff notations 6c (Ru2, Ru4) and 18f (Ru1, Ru3, Ru5), and nine lutetium sites at 3a (Lu1), 3b (Lu9), 6c (Lu8), and 18f (Lu2−Lu7).…”

“…As the electron affinity of ruthenium is higher than that of lutetium, 101 vs. 33 kJ/mol [15,16], {Ru 11 Lu 20 } could be regarded as a polar intermetallic compound. The sequence of the atoms, more negative to more positive in the waved brackets, is used in analogy to anti-Werner cluster complexes [12].…”

“…These polyhedra occur in a 3:1:3:1:3 ratio, hence seven ruthenium atoms out of eleven, in {Ru 11 Given that the analogy between the three-dimensional polar intermetallic compound {Ru 11 Lu 20 } and the one-dimensional polar intermetallic incorporated as a cluster chain in the anti-Werner cluster complex {Ru 5 Lu 20 }I 24 is accepted, the crystal structure of {Ru 11 Lu 20 } may be described as a connection between seven {RuLu 8 } (cube and square antiprism in a 4:3 ratio), one 1-4-4 {RuLu 9 } and three 1-5-4 {RuLu 10 } polyhedra. As Figure 1 shows, the connection between these polyhedra is surprisingly complex.…”

“…A plethora of reduced rare-earth metal halides at the borderline between metal and salt have been obtained within the last decades [1][2][3][4][5][6][7][8][9][10][11][12]. These contain cluster complexes, most frequently of the "6-12" type, in which octahedral metal clusters {R 6 } are surrounded by twelve halide ligands (X) capping all the edges.…”