Metal-free organic ligands

Vanadyl salen is readily converted at 100°C with H2S in the absence of a catalyst to a vanadium sulfide and a free organic ligand (or decomposition products). Vanadyl phthalocyanine is more stable with respect to ring attack and demetallation. Rates relative to catalytic reactions have not been measured. If VO-salen is an appropriate model of vanadium binding in asphaltenes, asphaltenic metals are more readily converted to sulfides under hydrotreating conditions than the porphyrinic metals. This suggests... 

Complexes of Me [14]-4,1 l-dieneN4 are, however, more conveniently prepared by reaction of the dianiono salt of the free organic ligand with metal carbonates or acetates in methanol or water-methanol mixtures. The isolation of the free organic ligand salt is achieved by the reaction of the monoperchlorate, or similar salt of ethylenediamine, with acetone or mesityl oxide (4-methyl-3-penten-2-one). The material can also be isolated from the reaction mixture produced by tris(ethylenediamine)iron(lI) perchlorate and acetone. The preparations described here involve the reaction of the ciperchlorate or bis(trifluoromethanesulfonate) salt of Me [14]-4,1 l-dieneN4 with the appropriate metal ion. 

The side reactions can considerably change the concentration of the free metal ion and the free organic ligand. To account for their effect on the main equilibrium, the side-reaction coefficients qcm, Kl and Mml as defined by Ringbom et al. need to be introduced into the stability constant (106). The side reaction coefficients are, of course, functions of the equilibrium constants of the side reactions if [M ] is the conditional concentration of M (all the forms of M not complexed with L), [L ] is the conditional concentration of L (all the forms of L not coordinated by M) and [ML ] is the conditional concentration of ML (the metal complex present in all the forms, even as mixed complexes, then the mathematical relationships to describe m, ocl and aML are ... 

The moiety denoted as I is the initiator group. It can be as simple as a free radical or as complicated as a transition metal atom bonded to organic ligands and located on a catalytic support. The next step in the polymerization is propagation, i.e., the repeated insertion of monomer units into the chain to create an incrementally longer chain... 

There are a number of particular technical advantages associated with the formation of coloured metal complexes. Commonly, the transition metal complexes of a coloured organic ligand exhibit lightfastness which is significantly better than that of the free ligand. An explanation that has been offered for this effect is that coordination with a transition metal ion... 

Complexation, or chelation, is the process by which metal ions and organic or other non-metallic molecules (called ligands) can combine to form stable metal-ligand complexes. The complex that is found will generally prevent the metal from undergoing other reactions or interactions that the free metal cation would. Complexation may be important in some situations however, the current level of understanding of the process is not very advanced, and the available information has not been shown to be particularly useful to quantitative modeling (5). 

---