Dimolybdenum Compounds

Chart 6.2 Possible structures of dimetal quintuply bonded compounds. 

A summary of all the structural parameters associated with crystaUographically characterized quintuply bonded compounds is given in Table 6.7. The formal shortness ratio (FSR) for a given bond was defined by Cotton [1] as follows  

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Although the redox reactions in Sch. 12 have not been achieved electrochemically, they illustrate another type of redox-induced structural change in a dimolybdenum compound with a sulfur-rich coordination sphere. In this case, Mo2(/r-S)2 ring opening in 18 (cleavage of Mo—Mo and Mo—S bonds) is associated with the exposure of vacant coordination sites, and the uptake of two carbonyl ligands in 17 [7, 53]. 

Using mixed-valence dimolybdenum compounds, i.e. involving an element with only about 25% of the naturally occuring isotope mixture bearing a nuclear spin /= 5/2), one has to analyse the EPR spectra more carefully... 

Because of the extieme reactivity of MoW(0200(0113)3)4, chromatographic methods for sepaarting the mixture were very difficult to apply. Thus it was not possible to obtain the pure, neutral mixed-metal compound. However, this greater reactivity could be advantageous in preparing a pure mixed-metal compound. It was natural to investigate the reaction with iodine with the expectation that the mixed-metal compound would react preferentially if a limited quantity of oxidant was available. The success of the method exceeded expectations, but it was surprising that a simple iodide salt was obtained rather than the triiodide salt as with the dimolybdenum compounds. This difference probably facilitates separation since the possibility of solid-solution formation between oxidized products is diminished. 

We provide herein optimized syntheses for a selected array of supramolecular compounds containing quadruply bonded M02" units, as well as the synthesis of the dimolybdenum compounds used as precursors. These syntheses are general and can be used for a variety of linkers, but only one example is provided for each structure type. However, an effort has been made to list other linkers that we used successfully. 

A variety of protocols exist for evaluating bond orders in molecules [48] and the bonding in [Cp Mo(p,-02CMe)]2(P -PMe2)(p.-Me) and [CpMo(p.-02CH)]2-(p,-PH2)(p.-X) was assessed using the Mayer bond order [49], that has also been used in other inorganic systems [50, 51]. The Mayer bond orders for a series of dimolybdenum compounds are summarized in Table 4, which provide several important comparisons. Firstly, the Mayer bond order of 0.72 for [Cp Mo-... 

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