Ligands mixed-metal complexation

Mukherjee, G.N. and Sahu, H.K. (1998) Multimetal multiligand complexes. Part I. Equilibrium study on the formation and stability of mixed ligand mixed metal complexes of cobalt-, nickel-, copper-and zinc (n) with aspartate and imidazole in aqueous solution. J. Indian Chem. Soc., 75, 143-147. 

Patel, R.N., Shrivastava, R.P., Singh, N., Kumar, S., and Pandeya, K.B. (2001) Equilibrium studies on mixed-ligand mixed-metal complexes of copper(II), nickel(II) and zinc(II) with glycylvaline and imidazole. Indian / Chem., 40A, 361 -367. 

The red tetrathiomolybdate ion appears to be a principal participant in the biological Cu—Mo antagonism and is reactive toward other transition-metal ions to produce a wide variety of heteronuclear transition-metal sulfide complexes and clusters (13,14). For example, tetrathiomolybdate serves as a bidentate ligand for Co, forming Co(MoSTetrathiomolybdates and their mixed metal complexes are of interest as catalyst precursors for the hydrotreating of petroleum (qv) (15) and the hydroHquefaction of coal (see Coal conversion processes) (16). The intermediate forms MoOS Mo02S 2> MoO S have also been prepared (17). 

Multinuclear mixed-metal complexes can be formed with carboxylate ligands. 

Other first-generation dendrimers built around multichelating ligands are the trinuclear complexes 29 - 38 [50-52] and several hexanuclear complexes (for representative examples, see 39 and 40) [53]. In all of these compounds, the photophysical properties are equivalent to those of their building blocks. In the mixed-metal complexes 31 and 34 [50b] the Ru(II)- and Os(II)-based chromo-phores are only weakly-coupled and a dual luminescence is observed. 

Because Ni(CO)4 is volatile (b.p. 43 °C) and cobalt will not react under these conditions, this process afforded a method for separating Ni from Co by the process now known as the Mond process. Although there are many complexes known that contain both carbonyl and other ligands (mixed carbonyl complexes), the number containing only a metal and carbonyl ligands is small. They are known as binary metal carbonyls, and they are listed in Table 21.1. The structures of most of these compounds are shown later in Figures 21.1 through 21.3. 

In the mixed-metal complex [WCI(py)(PMePh)3(//3-N2)l2(AICl2)2, both WNN linkages are essentially linear, and the four metal atoms and two /2.3-N2 ligands almost lie in the same plane, as shown in Fig. 15.1.5(d). 

Catalytic turnover has also been seen in radical relay chlorinations in which the template is temporarily linked to the substrate in a mixed metal complex. The steroid phosphate (22) and catalytic ligand... 

Catalytic turnover has also been seen in radical relay chlorinations in which the template is temporarily linked to the substrate in a mixed metal complex. The steroid phosphate (22) and catalytic ligand (23) both bind to zinc in a mixed complex, and the iodine atom of (23) directs chlorination of (22) at C-9 with reasonable selectivity (Scheme 25). Five or more turnovers are seen, when only 10% of the catalyst (23) is used. ... 

Ooi and co-workers adopted an elegant synthetic approach to the mixed-metal complexes of 4-methylpyridine-2-thiolate (4-mpyt). This approach includes the initial preparation of mononuclear complexes [M(4-mpytH)4]Cl2 (M = Pt, Pd), in which all four 4-mpytH ligands coordinate to with sulfur-donor atoms (84,102). The structure of the mononuclear Pd(II) complex with nonsubstituted pyridine-2-thiolate, [Pd(pytH)4]Cl2, is shown in Fig. 16 (84). These mononuclear complexes can be further reacted with the second metal ion to give mixed-metal dinuclear complexes. 

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