Multinuclear systems

The next development was a multinuclear system, which could potentially be used for measurements at low temperature using proton, fluorine and carbon. The system consisted of 0.25 ml of perdeuterated toluene, 0.25 ml of CbFe and 5.0 ml of CHFCI2. However, for - C the chemical shift of the methyl carbon of the perdeuterated toluene showed only a weak temperature dependence of 0.004 ppm K . ... 

It is hoped that the above examples provide an indication of the role metal NMR can play in characterizing certain organometallic and inorganic complexes. In favorable cases, it may be seen that metal NMR provides the most direct insight to the structural details of multinuclear systems, and to the dynamics and mechanism of exchange processes occurring around the metal center. 

I) of 5/2. For a mononuclear system, six hyperfine lines are predicted. However, for a multinuclear system containing n Mn ions, as many as 6" lines may be observed. This gives rise to a rich EPR spectroscopy among polynuclear manganese complexes, which has been used extensively in the study of biological manganese systems and model complexes. 

The aromatic moiety in phenylboranes and phenylb-orates may serve as a 6-electron tt donor ligand to transition-metal complexes. Half-sandwich complexes of chromium, Mes2[B( -Mes)Cr(CO)3] (56), MesB[jj -MesCr(CO)3]2 (57), and B[ -MesCr(CO)3]3 (58), containing trimesitylborane as a ligand have been prepared and structurally characterized. The Cr(CO)3 moieties interact weakly in the multinuclear systems (57) and (58) as shown by... 

Metal centers may be introduced into metallodendrimers and metallostars at a number of conceptually different sites. A convenient classification has been introduced by Balzani and co-workers and is used here in a slightly modified form. Conceptually, the simplest site for metal ion incorporation is at the center of the complex. In principle, a mononuclear complex with dendron-functionalized ligands could be regarded as a metallodendrimer, although this chapter concentrates upon multinuclear systems. 

There is currently a drive toward the design and preparation of multinuclear systems. Their interest stems from the same origins as the mononuclear variants however, the interesting photophysical and magnetic properties of the Ln series can be enhanced and/or altered when in close proximity with other 4f metal centers. 

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