Ligand methods

Fabiato, A. (1988). Computer programs for calculating total from specified free or free from specified total ionic concentrations in aqueous solutions containing multiple metals and ligands. Method. Enzymol. 157 378-417. 

Ligand Method TCC) Medium Log of equilibrium constants, remarks Ref. 

Three methods can be followed for the synthesis of a SIB catalyst (i) zeolite synthesis around the metal complex (ii) template synthesis and (iii) the flexible ligand method. 

Neutral ligand method, for transition metal complex electron counting, 1, 4... 

The majority of ruthenium(II) compounds which have been observed to be luminescent are complexes of aromatic heterocyclic chelating ligands. Methods of synthesizing such complexes are reviewed and recommendations made (where considered possible) as to the best procedures. 

Gamovskii, A.D. Vasilchenko, I.S. Garnovskii, D.A. Modern Aspects of Synthesis of Metal Complexes. Fundamental Ligands Methods. LaPO Rostov-on-Don, 2000, 354... 

On the basis of a large amount of experimental material, it was shown that there are much more complex compounds of N-coordinated azines [synthetic method A, transformation (4.13)] in comparison with complexes with analogous n-coordinated ligands (method B). The mentioned reactions (4.13) represent a modern state of competitive coordination of pyridine and its C-substituted derivatives [11,15,55,56] ... 

The flexible ligand method, consisting of the tetramerization of pyrrole and an aldehyde, can be used for the entrapment of metallo-porphyrins (MePOR) in situ in the supercages of faujasite-type zeolites (Scheme 10.7).[74]... 

Complexation via the ligand method of more than 70 % of the Cu and Fe ions in zeolite Y with a mixed tridentate NJ f,O-ligand such as (2-hydroxymethyl) (2-methyl-pyridine)amine (Hbpa) was reported, yielding entrapped Fe(bpa) (8) together with residual uncomplexed rhombohedral Fem with an ESR signal at g = 4.3 and Fe-Fe interactions with g = 2.0/1121 When a more than stoichiometric amount of Hbpa... 

Despite the fact that more than a decade ago the formation of a square planar Co2+complex was already demonstrated to be very difficult in faujasite,[119] further claims of its entrapment continued to appear. The ESR cobalt signature does not correspond to that of solution or solid Co(salen). Addition of the hexadentate H2bbpen ligand (14) to CuY via the ligand method resulted in a degree of coordination with iron ions of less than 46 %.[112]... 

Figure 11 Schematic representation of techniques used for solubilized and immobilized affinity ligands in polyacrylamide gels. (A) Solubilized ligand method the ligand can move freely in the gel-buffer system. (B) Macroligand method the solution of acrylamide contains the macroligand that becomes entrapped within the gel matrix after polymerization. (C) Chemically bound ligand direct copolymerization of polyacrylamide gel with the copolymerizable derivative of the ligand. (Reproduced with permission from Ref. 13.)...

In order to gain more direct access to these bicyclic ligands, methods have been developed which allow the formation of the macrobicycle in one step. The tripod-tripod coupling is an example of this method (Fig. 5.2) which may be performed without the need for high-dilution conditions. The synthesis of the bis-tren macrobicycle, 17, illustrates this approach.3... 

Similarly, five-membered rings can be synthesized by either addition of excess HFA to the complexes with exchange of ligands (method a) or by ring expansion of the corresponding metallaoxiranes (method b) [Eq. (121)]. 

In some cases the presence of a metal reducing agent is superfluous since PF3 can act as both a reducing agent and as a ligand (method E). 

There is one report (193) of the formation of a hexa-l,3-dienemetal complex formed by a coupling reaction of the ally] ligands (method C) in the reaction of [Fe(PF3)5] with allyl chloride. 

There is only one report to date of the simple addition of PF3 to an /3-allyl-metal complex containing no other ligands (method A), namely,... 

A formal analogy is often drawn between the linear bonding modes of both ligands. NO" " is isoelectronic with CO therefore, in its bonding to metals, linear NO is considered by electron-counting scheme A as NO", a 2-electron donor. By the neutral ligand method (B), linear NO is counted as a 3-electron donor (it has one more electron than the 2-electron donor CO). 

Flexible ligand method. 0.9 g of 1,2-phenylenediamine were slowly added with stirring to 2 g of salicylaldehyde. After 10 minutes stirring, the mixture was allowed to cool down and the product was transferred to 40 mL of ethanol. The solids were filtered off, recrystallized from ethanol and dried in vacuo overnight. 1 g of CoNaY was mixed with 2 g salophen and heated in an open tube to 450 K with continuous stirring for 12 hours. The molten slurry was allowed to cool, and the zeolite was soxhiet extracted with methylene chloride. The solid material was dried in vacuo overnight. 

The basic approach to prepare Co(II)-complexes of salen (N,lSr-bis(salicylidene)ethylene-diamine)-type molecules is the flexible ligand method [9]. In this process the Schiffbase ligand can diffuse by twisting into the zeolite where it becomes too large to exit by complexation with the cobalt ion. The flexible ligand method, however, was not usefiil for the preparation of Co-salophen/ zeolite catalyst, because the product was inactive in the oxidation reactions. The salophen molecule does not seem to be flexible enough and can not get into the zeolite to produce the suitable complex in the supercage. 

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