Lanthanide complexes clusters

As a group of typical metal elements, lanthanide elements can form chemical bonds with most nonmetal elements. Some low-valence lanthanide elements can form chemical bonds in organometallic or atom cluster compounds. Because lanthanide elements lack sufficient electrons and show a strong repulsive force towards a positive charge, chemical bonds between lanthanide metals have not yet been observed. Table 1.4 shows that 1391 structure-characterized lanthanide complexes were reported in publications between 1935 and 1995 and these are sorted by chemical bond type. 

Figure6.32 Structure of the cationic cluster complex [Eu4(p.3-0H)4(nic)6(H20)8]2 + (nic= nicoti-nate). Hydrogen atoms are removed for clarity [57]. (Redrawn from X. Kong et al., Hydrolytic synthesis and structural characterization of lanthanide hydroxide clusters supported by nicotinic acid, Inorganic Chemistry, 48, 3268-3273, 2009.)...

Reaction of tetranuclear lanthanide octahydrides with styrene provides lanthanide benzylic allyl heptahydride complexes through the insertion of a styrene molecule into one Ln-H bond. The lanthanide benzylic allyl complexes can be considered as the intermediates of styrene hydrogenation. Indeed, both the lanthanide octahydrides and the lanthanide benzylic allyl complexes can catalyze styrene hydrogenation efficiently in the presence of H2 [89]. Lanthanide hydrides react with 1,3-cyclohexadiene to form lanthanide allylic complexes via 1,4-addition [90]. However, these lanthanide hydride clusters can not catalyze the polymerization of styrene and 1,4-cyclohexadiene. 

The only relevant Group 3 polynuclear complex, [Y8(/i4—0)(/i3—OH)i2(/r—Se4)4Cl2(DMF)i0] 6DMF is prepared from YC13 and polyselenide in DMF. It has an octanuclear core, supported by oxo, hydroxo, and tetraselenido bridges with no Y—Y bonds. No Sc or actinide chalcogenide clusters are known. Lanthanide/selenido clusters have recently been isolated.14... 

A variety of the metal-metal bonded complexes or clusters also provide a foothold for the studies of f-orbital participation. Examples of such organo-lanthanide complexes include cyclopentadienyl lanthanides with lanthanide-to-transition metal bonding L(n -C H ) LnW (n -C H )(CO), (n -C H.) LnMo(n --C H )... 

A large number of dinuclear lanthanide complexes have been reported in the literature. No specific efforts will be made for their general discussion. However, where appropriate, such species are included to provide necessary context for the discussion of the formal assembly of higher-nuclearity clusters from these well-defined, recognizable building blocks. 

Other phenolato moiety-containing ligands have also been utilized for the assembly of lanthanide-hydroxo clusters. Eor instance, a [Sm4(/i3-OH)4] " core-containing cluster was obtained by exposing the dimeric Sm(ll) complex [Sm2(SP-SP)(THE)3] (SP-SP = C-C bonded... 

Hydrido clusters of this type are isolated by reacting bis-alkyl lanthanide complexes bearing a cyclopentadienyl ligand sterically hindered by a -SiMcs substituent or other bulky and noncoordinating substituents (Hou et al., 2007 Figure 53). 

Cationic lanthanide hydrido clusters have also been s)mthesized by treating the neutral polyhydrido clusters with Ph3CB(CgF5)4 (Li et al., 2006b). The structures of two such complexes are illustrated in Figure 57. 

Reduction of dinitrogen molecule by divalent lanthanide complexes has been a popular subject in coordination and organometallic chemistry of the lanthanide elements. In the course of these studies, a large number of polynuclear lanthanide clusters featuring a core of lanthanide atoms organized around a dinitrogen unit have been obtained and structurally characterized. 

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