Metal complexes, pore loading

Transition metal complexes encapsulated in the channel of zeolites have received a lot of attention, due to their high catalytic activity, selectivity and stability in field of oxidation reactions. Generally, transition metal complex have only been immobilized in the classical large porous zeolites, such as X, Y[l-4], But the restricted sizes of the pores and cavities of the zeolites not only limit the maximum size of the complex which can be accommodated, but also impose resistance on the diffusion of substrates and products. Mesoporous molecular sieves, due to their high surface area and ordered pore structure, offer the potentiality as a good host for immobilizing transition complexes[5-7]. The previous reports are mainly about molecular sieves encapsulated mononuclear metal complex, whereas the reports about immobilization of heteronuclear metal complex in the host material are few. Here, we try to prepare MCM-41 loaded with binuclear Co(II)-La(III) complex with bis-salicylaldehyde ethylenediamine schiff base. 

A number of research groups have investigated the uptake of redox active metal complexes as a precursor to the formation of metal nanoparticles inside MOFs. This area has recently been reviewed by Suh and co-workers, hence only representative examples will be discussed. In most examples, pores within the MOF are loaded with a metal complex or salt through CVD or through immersion of the MOF in a solution containing the complex, and subsequent chemical reduction gives the metal nanoparticle embedded in the MOF. The MOFs with embedded nanoparticles may have enhanced H2 storage because of M-H2 interactions to the particles, and they are effective solid-state catalysts. " ... 

Pt(NH3) ions since the molecular dimensions of these metal complexes exceed the pore apertures. Platinum was incorporated during the synthesis of the zeo-hte by mixing solutions of K2PtCl4 with solutions of sodium metasiUcate and sodium aluminate in the required amounts. More recently, Davis et al. [129,130] prepared intrazeoHtic 2-5 nm ruthenium particles in NaA and CaA zeoHtes by addition of [Ru(NH3)5Cl] CI2 to the hydrothermal synthesis mix of zeolite A. This technique of metal loading has never been widely used to prepare metal clusters in zeolites but is frequently employed to substitute lattice aluminum in zeoHtes or aluminophosphates by metal ions. 

To improve the characterization of various tantalum surface complexes, their preparation has been extended to a mesoporous silica MCM-41 (lOOOm g, 28A pores), to increase the metal loading. In addition, for NMR studies, the initial complex Ta(CH2CMe3)3(=CHCMe3) has been 10% labeled with on the a carbon with respect to the metal center [57]. 

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