Lanthanides holmium

The high-temperature polymorphic form for most of the rare earth metals just before melting is the bcc structure. Four of the trivalent lanthanides (holmium, erbium, thulium and lutetium) are monomorphic and do not form a bcc structure before melting at atmospheric pressure (see fig. 4). However, the bcc phase can be formed in holmium and erbium by the application of pressure (< 1 GPa), see section 3.7.1. The existence of the bcc phase in the lanthanides has been correlated with the d occupation number, which decreases along the lanthanide series, but increases... 

On the other hand, lanthanides with 100% isotopical purity such as terbium or holmium are preferred to simplify the operation and minimize decoherence in spin qubits. In this respect, the existence, for some lanthanides, of a manifold of electronuclear states can provide additional resources for the implementation of multiple qubit states within the same molecule [31]. All atoms in the first coordination sphere should be oxygen, and the sample should be deuter-ated if the compound contains hydrogen, to avoid interaction with other nuclei spins. Again, POM chemistry has been shown to provide ideal examples of this kind. 

Holmium is a crystal-like, solid rare-earth with a metaUic luster. It is one of the more scarce elements of the lanthanide series. It is soft, hke lead, and can be hammered and pounded into thin sheets. 

Holmium is the 12th most abundant of the rare-earths found in the Earths crust. Although it is the 50th most abundant element on Earth, it is one of the least abundant lanthanide metals. It is found in gadolinite and the monazite sands of South Africa and Austraha and in the beach sands of Florida and the Carolinas in the United States. Monazite sand contains about a 50% mixture of the rare-earths, but only 0.05% by weight is holmium. Today, small quantities of holmium are produced by the ion-exchange process. 

Einsteinium has homologous chemical and physical properties of the rare-earth holmium (g Ho), located just above it in the lanthanide series in the periodic table. 

Holmium is obtained from monazite, bastnasite and other rare-earth minerals as a by-product during recovery of dysprosium, thulium and other rare-earth metals. The recovery steps in production of all lanthanide elements are very similar. These involve breaking up ores by treatment with hot concentrated sulfuric acid or by caustic fusion separation of rare-earths by ion-exchange processes conversion to halide salts and reduction of the hahde(s) to metal (See Dysprosium, Gadolinium and Erbium). 

A consequence of the lanthanide contraction is that when holmium is reached, the increase in size from n = 5 — n = 6 has been lost and Ho34- is the same size as the much lighter Y1+ (104 pm) with correspondingly similar properties.44 The contraction docs not proceed sufficiently far to include Sc3+ (88 pm), but its properties may be extrapolated from the lanthanide series, and in some ways it provides a bridge between the strictly lanthanide metals and the transition metals... 

The lanthanide elements were once known as the rare earths. Lanthanides, however, are not particularly rare. Holmium, one of the less common lanthanides, is still 20 times more abundant than silver on Earth. The rare earth name comes instead from how difficult it was for early chemists to separate all of the lanthanides from one another. Because these elements add electrons to an inner shell, they all show the same face to other elements. This makes them all react very similarly with other elements, and it can be tricky to tell them apart. 

Lanthanide bromides and iodides have found important applications in a completely different field. They are added as additives in high-pressure discharge lamps in the lighting industry to improve the arc stability and the colour quality. The latter is due to the contribution of the multiline spectrum of the doped rare earths which are added to the salt mixture. Lanthanide trihalides of dysprosium, holmium, thullium, gadolinium and lutetium are used frequently for this purpose (Hilpert and Niemann, 1997). 

The only complexes of lanthanum or cerium to be described are [La(terpy)3][C104]3 175) and Ce(terpy)Cl3 H20 411). The lanthanum compound is a 1 3 electrolyte in MeCN or MeN02, and is almost certainly a nine-coordinate mononuclear species the structure of the cerium compound is not known with any certainty. A number of workers have reported hydrated 1 1 complexes of terpy with praseodymium chloride 376,411,438), and the complex PrCl3(terpy)-8H20 has been structurally characterized 376). The metal is in nine-coordinate monocapped square-antiprismatic [Pr(terpy)Cl(H20)5] cations (Fig. 24). Complexes with a 1 1 stoichiometry have also been described for neodymium 33, 409, 411, 413, 417), samarium 33, 411, 412), europium 33, 316, 411, 414, 417), gadolinium 33, 411), terbium 316, 410, 414), dysprosium 33, 410, 412), holmium 33, 410), erbium 33, 410, 417), thulium 410, 412), and ytterbium 410). The 1 2 stoichiometry has only been observed with the later lanthanides, europium 33, 411, 414), gadolinium, dysprosium, and erbium 33). 

The term rare earth elements is sometimes applied to the elements La-Lu plus yttrium. The convenience of including La, which, strictly speaking, is not a lanthanide, is obvious. The reason for including Y is that Y has radii (atomic, metallic, ionic) that fall close to those of erbium and holmium and all of its chemistry is in the trivalent state. Hence it resembles the later lanthanides very closely in its chemistry and occurs with them in Nature. 

Lanthanide elements (referred to as Ln) have atomic numbers that range from 57 to 71. They are lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). With the inclusion of scandium (Sc) and yttrium (Y), which are in the same subgroup, this total of 17 elements are referred to as the rare earth elements (RE). They are similar in some aspects but very different in many others. Based on the electronic configuration of the rare earth elements, in this chapter we will discuss the lanthanide contraction phenomenon and the consequential effects on the chemical and physical properties of these elements. The coordination chemistry of lanthanide complexes containing small inorganic ligands is also briefly introduced here [1-5]. 

Figure 9.15 ORTEP plot (upper) and unit-cell packing diagram of the complex [SmFe] [99]. (Reprinted with permission from B. Yan, and Z. Chen, Cyano-bridged aqua(A, A -dimethylacetamide)(cyanoiron)lanthanides from samarium, gadolinium, or holmium nitrate and potassium hexacyanoferrate crystal structures and magnetochemistry, Helvetica Chimica Acta, 2001, 84, 817-829 (Figures 1 and 2). Wiley-VCH Verlag GmbH Co. KGaA.)...

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