Hexanuclear complexes

Divalent molybdenum compounds occur in mononuclear, dinuclear, and hexanuclear forms. Selected examples are shown in Figure 6. The mononuclear compounds are mostiy in the realm of organometaUic chemistry (30—32). Seven-coordinate complexes are common and include MoX2(CO)2(PR3)2, where X = Cl, Br, and I, and R = alkyl MoCl2(P(CH3)3)4, heptakis(isonitrile) complexes of the form Mo(CNR) 2 (Fig. 6d), and their chloro-substituted derivatives, eg, Mo(CNR)3CR. The latter undergo reductive coupling to form C—C bonds in the molybdenum coordination sphere (33). 

With [RUjfCOlij], dinuclear species 161 emerges (88JCS(D)1437). In contrast, with [Os3(CO) q(AN)J, two isomers, 162 and 163, result (88JOM (353)251). Isomer 162 enters the CO/AN monosubstitution reaction in acetonitrile in the presence of Mc3N0-2H20, the product on subsequent thermolysis forms the hexanuclear complex 164. 

Inspired by Gif or GoAgg type chemistry [77], iron carboxylates were investigated for the oxidation of cyclohexane, recently. For example, Schmid and coworkers showed that a hexanuclear iron /t-nitrobenzoate [Fe603(0H) (p-N02C6H4C00)n(dmf)4] with an unprecedented [Fe6 03(p3-0)(p2-0H)] " core is the most active catalyst [86]. In the oxidation of cyclohexane with only 0.3 mol% of the hexanuclear iron complex, total yields up to 30% of the corresponding alcohol and ketone were achieved with 50% H2O2 (5.5-8 equiv.) as terminal oxidant. The ratio of the obtained products was between 1 1 and 1 1.5 and suggests a Haber-Weiss radical chain mechanism [87, 88] or a cyclohexyl hydroperoxide as primary oxidation product. 

Arias, J., Baradaji, M. and Espinet, P. (2008) Mononuclear, dinuclear, and hexanuclear gold(l) complexes with (aza-15-crown-5) Dithiocarbamate. Inorganic Chemistry, 47, 1597-1606. 

The hexanuclear Ir111 complex [L IrCl2cp 6], in which L is based on the amino glycoside neomycin B (249), has been characterized by IR, 13C, and 31P NMR spectroscopy, and by FAB Ms419 The in vivo antitumor and antitrypanosomal effects of [IrY4Cl2]1 complexes,... 

Figure 31 Hexanuclear Ni11 cage complex (832) with an interstitical /i6-Cl atom2033 (reproduced by permission of the Royal Society of Chemistry).

Dithiocarbamates have been used as ligands for a long time. Recently the structure of [Ag(S2CNEt2)]6 has been reported and the compound is hexanuclear.1212 Complexes of the type... 

In compliance with the nuclearity principle, polynuclear clusters are subdivided into a number of other subgroups, e.g. hexanuclear, octanuclear, etc. The binuclear clusters of technetium may be classified according to the electronic structure of their Tc-Tc2 bonds. Then, the d4-d4 complexes with quadruple M-M bonds are the father of all binuclear complexes with Tc-Tc bonds. The addition or removal of electrons from Tc-Tc bonds [1,11] should result in a decrease in the formal multiplicity of M-M bonds. Thus, for instance, the formal multiplicity of Tc-Tc bonds of d3-d3 and d5-d5 binuclear complexes equals3 3, that of d4 d5 and d4-d3 complexes equals 3.5, etc. 

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. 

Studies on the cubic NLO properties of Mo/W-S/Se-Cu/Ag clusters have been reviewed,539-541 and some related species which contain pseudo-square planar Pd11 centers instead of CuVAg1 have also been investigated.542-545 However, such complexes, e.g., the hexanuclear windmill cluster... 

Apart from the gold(i) system, bis(mesityl)mercury(ii), which also possesses a heavy metal center with strong relativistic effects, has been used for the synthesis of the mixed metal silver(i) aryl complexes, [HgAg2(mes)X2]2 (X = OTf 13a (Figure 7), C104 13b).33 X-ray crystal structure analysis of 13a revealed its hexanuclear nature with the... 

---