Clusters comproportionation

Pyridyldiphenylphosphine forms a number of homo-and heteronuclear palladium dinuclear clusters with short Pd-M bonds (about 260 pm). They are usually made by comproportionation of a Pd(II) complex and a second complex in a low oxidation state, for example, Pd(0), Rh(I), Ru(0). For these derivatives, head-to-head and head-to-tail isomers are possible, but the latter seems to be preferred (Figure 2). The metal-metal bonds in these derivatives are not as reactive as in the corresponding dppm complexes and insertion reactions do not occur. Some single-bridged complexes, such as [Cp(CNR)Rh(/u.-PPh2Py)Pd(CNR)Cl]+ (Pd-Rh distance 263.1 pm) are also known. 

Figure 27. Summary of information for two intramolecular redox centers, including the potential separation for two independent and identical centers (Eq. 14), the electron-transfer series 15 and comproportionation reaction 16 for double-cubane clusters, and the compro-portionation constant (Eq. 17).

The cluster set 40 is merely one of a number with different bridging groups that can be conceived. An interesting question, but one difficult to explore experimentally because of the values of. com for comproportionation reaction 16 (Fig. 27), is that of electron-transfer rates between sub-... 

The comproportionation route is widely used and is very efficient when pure phases are desired, especially when the phase relationships are known. It led to a great variety of reduced rare earth haUdes, binary, ternary, and higher, simple and complex salts and such that incorporate metal clusters interstitially stabiUzed by a nonmetal atom or by a (transition) metal atom for example,... 

The Comproportionation Route 120 4.7 Layers of Edge- and Face-Connected Clusters 162... 

In the following, we will discuss only the comproportionation route and the metallothermic reduction route as the two most commonly used synthetic approaches to rare-earth metal/transition metal cluster complexes. 

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