Lanthanide metal cyanide

The complications which result from the hydrolysis of alkali metal cyanides in aqueous media may be avoided by the use of non-aqueous solvents. The one most often employed is liquid ammonia, in which derivatives of some of the lanthanides and of titanium(III) may be obtained from the metal halides and cyanide.13 By addition of potassium as reductant, complexes of cobalt(O), nickel(O), titanium(II) and titanium(III) may be prepared and a complex of zirconium(0) has been obtained in a remarkable disproportion of zirconium(III) into zirconium(IV) and zirconium(0).14 Other solvents which have been shown to be suitable for halide-cyanide exchange reactions include ethanol, methanol, tetrahydrofuran, dimethyl sulfoxide and dimethylformamide. With their aid, species of different stoichiometry from those isolated from aqueous media can sometimes be made [Hg(CN)3], for example, is obtained as its cesium salt form CsF, KCN and Hg(CN)2 in ethanol.15... 

Complex formation is useful for metal speciation and also for the separation of diverse metal ions. Among a variety of complexing reagents [20-22] cyanide is probably the most important. IPC separation of metal ions as metallocyanide complexes with a suitable cationic IPR is a reliable technique [23]. Complexation of trace level lanthanides with a-hydroxy isobutyric acid and separation under IPC condition shortened analysis time from days to minutes [24]. Flow injection was successfully coupled to IPC to simplify batch precomplexation detection limits were at sub-microgram per liter levels [2]. 

In this article the term organometallic compound includes alkyl and aryl derivatives of the rare earths—the transition metals of group III, scandium, yttrium, lanthanum and the lanthanides cerium to liitetium with covalent metal-to-carbon a-bonds, as well as the so-called 77-complexes with more than monohapto metal-to-carbon bonds, for example cyclopentadienyl and olefin complexes, metal acetylides, but not carbonyls, cyanides and isocyanide complexes. Derivatives of scandium, yttrium and lanthanum are included and discussed together with the compounds of the lanthanides, because of many similarities in the synthesis and the chemistry of these organometallic derivatives of the rare earths. 

A simpler but equally effective approach has been employed by Ward and coworkers [25] in the preparation of coordination polymers using luminescent anionic complexes. Here transition metals with emissive MLCT states act as effective sensMsers for lanthanide emission in the NIR [25]. In this case cyanide groups were used as bridging units starting from stable Ru " complexes and simple Ln salts. Examples include [Ru(Bipy)(CN)4] [26,27], [Ru(Phen) (CN)4] - [28], [Ru(Bpym)(CN)4] -, [Ru(CN)4]2([i-Bpym) 4- [29], [Ru(Hat)(CN)4] - [25], [Ru(CN)4]3(p"-Hat) -, [ Ru(CN)4 2([i -Hat)]4-, [Cr(CN)6]"-, and [Co(CN)6] - [30]. The advantage of this method is that the building blocks are already kinetically stable in solution and the solid structure is dictated by the coordination number adopted by the lanthanide ion (Fig. 9.5). 

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