Heterodinuclear systems

De Cola reported homo- and heterodinuclear systems in which the metallic fragments [Ru(bipy)3] and [Os(bipy)3] are bridged by a dithienylperfluorocyclopentene molecular switch, a phenylene group being used as a spacer [68-70]. 

In view of the low Nin/Niin redox potential of [NiFe] hydrogenase, the search for low-potential Nin/Niin complexes not only with pure S-donor but also with mixed N/S environment has been of major interest, and significant advances in this field have been reported.298,299 Various mononuclear systems are listed in Figure 1 according to their redox potentials (usually in DMF). Homodinuclear Ni2 and heterodinuclear NiM complexes with N/S donor ligands, in particular... 

Wozniak and coworkers described recently the first heterodinuclear bismacrocyclic transition metal complex 34 + (Fig. 14.5) that exhibits potential-driven intramolecular motion of the interlocked crown ether unit.25 26 Although the system contains transition metals, the main interaction between the various subunits, which also allowed to construct catenane 34+, is an acceptor-donor interaction of the charge transfer type. 

Exchange interactions in heterodinuclear transition metal complexes have attracted the attention of many researchers in the last few years. Nickel(II)-copper(II) dimers are, in a sense, the simplest systems to be investigated and several complexes containing paramagnetic nickel(II) and copper(II) ions have been reported, as pure complexes2985-2987 or as impurities in a parent lattice.2959,2987"2991 Magnetic susceptibility or EPR spectroscopy has been used to... 

Gunter and coworkers have synthesized a lateral macrobicyclic molecule 197 where a phorphyrin ring is capped by a bridging unit which contains a pyridino subunit. This model system for cytochrome c oxidase is in fact a heterodinuclear complex with iron(III) complexed to the porphyrin unit and copper(II) complexed to the lateral pyridino bridge. A series of these complexes have been made with... 

Most transition metal ions can react via pathways described by Equation 4.4 a few biologically relevant examples include FenFen > FeraFenl or Cu Cu1 > CunCun oxidations. Two low-oxidation state metal ions can be a part of a dinuclear complex. Alternatively, a mononuclear complex may undergo oxidation, forming dinuclear complexes in the oxidized form. Two metal ions in Equation 4.4 can be different in this case, exemplified by Cu f e11 systems, heterodinuclear oxidation products form. 

The method has been extended also to heterodinuclear species, i.e., systems in which two different metal ions are magnetically coupled, and to polynuclear compounds. ... 

Both dMMAO and dMAO systems conducted polymerization, but the former showed about 50 times higher activity than the latter. The polymers obtained with dMMAO and dMAO had high values of 290,000 and 209,000, respectively, and consequently the number of polymer chains N) in the dMMAO system was 30 times larger than in the dMAO system. The polydispersity (MJMj) of the polymer obtained with the dMMAO system was narrow (Mw/M = 1.16), whereas that with the dMAO system was broad MJM = 3.52). The low M value and the broad M / M in the dMAO system are mainly due to the poor solubility of dMAO in heptane. MAO and MMAO did not show activity under the same conditions, probably due to the formation of the heterodinuclear complex with the remaining R3AI. 

The Phillips catalyst, based on a Cr/2,5-dimethylpyrrole precursor and TEA as a cocatalyst, is the only commercial catalytic system for ethylene trimerization [164] and has thus been extensively studied [139, 140]. Based on DFT calculations, a redox mechanism involving a Cr(ll)/Cr(lV) couple has been proposed [154, 165]. Also, the pyrrole derivative ligand, able to interact with one or two metal centers through the nitrogen lone pair and/or the aromatic Jt-system, may play a key role for the stabilization of heterodinuclear Cr/Al species formed after activation. 

---