Molybdenum quadruple bonds

The molybdenum(II) carboxylates, Mo2(02CR)4, are key derivatives containing molybdenum-molybdenum quadruple bonds.1 First described by Wilkinson and coworkers in the early 1960s,2 they remain the key starting materials in (Mo2)4 + chemistry and they have been the objects of numerous physical and theoretical studies.1 The most commonly used method of preparation is the reaction between molybdenum hexacarbonyl and a carboxylic acid in an inert solvent such as 1,2-dichlorobenzene (DCB) [eq. (I)].3 Excellent yields of Mo2(02CR)4 can be obtained by... 

Molybdenum(ll) dimers display a slightly larger span of metal—metal distances than the quadruply bound rhenium(lll) units. Certain ligand types can be associated with fairly specific metal—metal bond lengths in the molybdenum species. Thus molybdenum quadruple bonds differ in this respect from the... 

An example of the model complexes that point the way to potentially fascinating polymers in the future is given by the tetranuclear species 6.21 [49]. Remarkable square arrays of molybdenum-molybdenum quadruple bonds with oxalate spacers have also been prepared by simple assembly procedures, as illustrated by the formation of the complex Mog(oxalate)4(N-N)g (6.22) (N-N = di(p-methoxyphenyl)forma-midinate) (Fig. 6.11) from [Mo2(N-N)2(NCMe)2] and [oxalate] " [52]. 

In fact, because Mo(II) is isoelectronic with Re(III), Cotton proposed that Mo2(02CCH3)4 contains a molybdenum-molybdenum quadruple bond. A vast... 

This species acts as a propene metathesis catalyst even at 0°C, Apparently clean oxidation, hydrogenation, and chlorination processes can be achieved from this material to afford new metal sites. The same coordination centre as shown in Eq. 6 can also be formed from Mo2(allyl)4 [94]. In that case adsorption at 0 C did not cause loss of propene rather the molybdenum-molybdenum quadruple bond is considered... 

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