Mixed-valence metal alkynyl complexes

In view of the rapid development in the synthesis of metal alkynyl complexes and the inherent advantage of the rigidity of such systems, attempts have been made by researchers to synthesize mixed-valence metal alkynyl [210, 211] and mixed-metal alkynyl complexes [64]. The incorporation of different metal centers to the organic spacer, which is usually achieved by the metalloligand approach, may provide a good handle to investigate the electron transfer and communication across the molecule. Isolation of mixed-valence homometallic species have... 

On the other hand, the ruthenium complex of ferrocenyl-alkynyl dimer shows a separation of redox potentials of two ferrocene units through the alkyne-Ru-alkyne ligand at 0.22 This result indicates that the mixed-valence state of ferrocenyl groups in Ru(-C=C Fc)2(dppm)2 complex are much more stable because of the strong donor-acceptor interaction through the ruthenimn core metal with two a-bonding alkynyl chains. The four oxidation states could be experimentally foimd for Ru(H =C Fc)2(dppm)2 complex (Fe(II)-Ru(II) Fe(II) Fe(III) Ru(II) Fe(II) Fe(III) Ru(II)-Fe(in) Fe(III)-Ru(III)-Fe(III)), where the redox potential of the ruthenium center is positively shifted as noted above. 

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