Cubanes metal complexes

Pores of such diameter are likely to allow passage of bulky metal complexes such as Co404(02CPh)4(4-CNpy)4 that is estimated to have the largest molecular dimension of ca. 15 A (= 1.5 nm). Thus, cubane-like cluster complexes may be expected to bind on the inner walls of the pores of CMS-CH2CH2CO2H. The BET surface areas and pore volumes for the supported materials decrease considerably following immobilization of the tetrameric metal complexes. 

The mercurial Hg[Fe(CO)3NO]2 reacts with elemental sulfur S8 to yield the cubane-type cluster [Fe4S4(N0)4] (36, 37) it is not therefore entirely unexpected that metal complexes rich in sulfur can likewise react with this mercurial to produce novel heterometallic nitrosyls. 

Kalinina IV, Fedin VP. Cubane chalcogenide complexes of group IV-VI metals Synthesis, structure, and properties. Russ J Coord Chem 2003 29 597-615. 

Transition-metal complexes of [Sn( a3-NR)]4 cubanes have also been reported. The reaction of Fe2(CO)9 with [Sn( a3-NSiEt3)]4,8, produces the complex [Sn()a3-NSiEt3)]4-2Fe(CO)4,36, in 82% yield, even when an excess of Fe2(CO)9 is used. The presence of only two broad signals for the ethyl substituents in the NMR spectrum suggests that the iron centers scramble in solution, cf. 35. A series of related transition-metal complexes of 4 have been mentioned in reviews, however no details have been reported for the complexes 37a-d. ... 

The 0X0 cluster 30a has also been used to prepare a handful of metal complexes. The aluminium complex 46 was obtained in 81% yield from the reaction of 30a with 1.5 equivalents of AlMes no coordination to the tin centers was observed. Thermolysis of 46 resulted in the generation of the cubane 4. The complexes 47 and 48 were prepared in THF by the reaction of 30a with LiCl and FeCh, respectively, in a 3 1 molar ratio. " Both complexes exhibit the coordination of three oxo cubanes to the metal center strong metal-oxygen bonding is indicated by the short metal-oxygen bond distances [47,... 

The fully oxidized nature of cluster (7) generates significant reactivity properties. The cluster cannot be reversibly reduced, but it does react with FeCl2 to form an Fc4S4 cluster and with reduced metal complexes to afford heterometal cubane-type clusters.Reaction... 

Transition Metal Complexes with a Cubane Core. 84... 

Like protons, transition-metal ions are strongly acidic and they can, in principle, add to both the C—H and C—C bonds of alkanes. As already noted in the section on proton affinities (Table 1) strained cycloalkanes are intrinsically more basic than open-chain alkanes, and the reaction of cyclopropane with Pt((II) to form a platinacyclo-butane (equation 14) was the first reaction of a formally saturated hydrocarbon with a transition-metal ion . The driving force in this reaction is relief of the strain associated with the small ring. The resulting metallacyclobutane is essentially free of ring strain. Many low-valent transition-metal complexes have been found to react with cycloalkanes. Metal ions convet the strained hydrocarbons quadricyclane , cubane , bicyclo-[2.1.0]pentanes , bicyclo[3.1.0]hexanes , bicyclo[4.1.0]heptanes and bicyclo-butanes into less strained isomers (usually cyclohexanes). 

Desymmetrization to the co-kernel subgroups will become important in connection with the mechanism of reactions involving transition metal complexes as well as of highly symmetric organic molecules, such as cubane or tetrahedrane. A Table of Kernels and Co-Kernels is, therefore, included as Appendix B, but reference to it will be deferred until the the ideas developed in this chapter are extended beyond single atoms, first to diatomic and then to polyatomic molecules. 

Strained Carbocyclic Systems.—A large number of examples of catalysis of valence isomerization of strained ring compounds by transition-metal complexes has been considered during the period covered by this Report. The most commonly used metal centres are rhodium and silver, and much of the interest in this field is concentrated on determining and accounting for the differences, in effectiveness and in the nature of the products, between rhodium catalysts and silver catalysts. Thus, for instance, in the presence of [RhCl(nor)]2 or [RhCl(cod)]2, cubane (1) isomerizes to the diolefin (2), but in the presence of silver perchlorate cubane isomerizes to cuneane (3). ... 

In recent years, sulfur, both in its atomic and molecular (e.g., S2) forms, has been noted to be a remarkably versatile ligand in transition metal complexes. It has been found to bridge two, three, or even four metal atoms and thus readily lends itself to the study of polynuclear complexes. One of the classic examples is [CpFeS]4 (Cp = tj -CjHs), a cubane cluster containing triply bridging sulfiir atoms. An important property of these cluster compounds is their general tendency to undergo reversible redox reactions via modification of metal-metal interactions. For example, [CpFeS]4 can exist in several different molecular oxidation states, ... 

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