Chemical shifts, dithiocarbamate complexes

The ambient temperature solution NMR spectra of the tris(dithiocarbamate) complexes, including those of Al (see above), show the complexes to be fluxional on the NMR chemical shift time scale. The stereodynamics can be quite complex with several different processes possible, namely, (1) a metal-centered rearrangement of the ligand polyhedron, (2) reversible ligand dissociation, (3) restricted rotation about the single N—C bonds of (bulky) N substituents. 

Some of these triply bridged complexes have been investigated extensively by cyclic voltammetry (CV) and Mo NMR spectroscopy (978). In the former, two successive one-electron reductions are observed, potentials correlating well with the Taft polar substituent constants for the dithiocarbamates, while Mo chemical shifts vary between 5 329 (R = Me) and 354 (R = i-Pr), the line width increasing as a function of dithiocarbamate steric bulk. 

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