Hexanuclear complexes, formation

The demonstration of the formation of a hexanuclear zinc complex with the S-donor ligand 2-aminoethanethiolate, containing Zn3S3 and Zn4S4 cyclic units, contributes to the building up of a pattern of polynuclear complex formation based on coordination preferences of the metal ions involved (320) - reaction of Zn2+ with salicylideneamino ligands and pyrazine can give linear tetranuclear complexes (321). Another hexanuclear zinc complex appears in the section on supramolecular chemistry below (Section VII.D). 

An unprecedented cyclic structure was found in a rare example of an organo-actinide complex associated via 7r-interactions. The reaction of ThBr4(thf)4 in THF with one equivalent of cyclopentadienyl thallium followed by treatment with three equivalents of KOPr led to the formation of the highly unusual hexanuclear complex [(C5H5)Th2(OPr )v]3, 106 [102]. In the cyclic molecule three dinuclear Th2(OPr )v units are connected by bridging cyclopentadienyl ligands. The... 

When compound 2 was instead treated with a large excess of bpy, besides Hpz molecules, one formate ion was also removed and exchanged with an OH ion, likely coming from adventitious water. Two bpy molecules join two trinuclear fragments yielding the hexanuclear complex [ Cu3(/Z3-0H)(/z-pz)3(HC00)(H20)()u-bpyHbpy)2 (0H)2](bpy), 12, and a crystallization bpy molecule is also present [17]. 

Various iron salts and mononuclear Fe or binuclear Fe complexes with a N,0 environment, biomimetic to methane monooxygenase complexes, have been applied to the oxidation of cyclohexane with various oxidants [6u,v,7a-g], but their catalytic activity is usually modest, with the exception of a hexanuclear Fe(III) compound derived from p-nitrobenzoic acid, which gives the highest total yield to Ol/One of about 30% [7a]. Moreover, most of these complexes are often unstable and very expensive. A hexanuclear heterotrimetallic Fe/Cu/Co complex bearing two Cu(p-0)2Co(p-0)2Fe cores, prepared by self-assembly, oxidizes cyclohexane with aqueous HP, with a maximum yield to Ol/One of 45%, virtually total selectivity to the two compounds, and preferred formation of cyclohexanol [7hj. The remarkable activity of the Fe/Cu/Co cluster was associated with the synergic effect of the three metals. 

The lower nuclearity clusters [Mo5Cl13]2 were isolated from MoCls in AlCl3/KCl/BiCl3/Bi melts that led to the hexanuclear species (17). This is the only intermediate isolated from reaction mixture that produces the Mo6C18 4+ core. Solution chemistry has yielded Mo2, Mo3, and Mo4 halide species from mononuclear molybdenum complexes, suggesting that a nucleation process similar to that proposed for the tungsten systems may take place during the formation of hexanuclear molybdenum clusters (18-22). 

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