Transition metal complexes with isothiocyanates

Ammonium dithiocarbamates can be prepared through reaction (11). With HC1 or H2S04 at lower temperatures the free acids are formed. Only one transition metal complex (37) is known, with a pseudo-octahedral coordination of Ni four sulfur atoms of the dithiocarbamate in the equatorial plane and two pyridine solvent molecules at the apical positions. Sulfides can be eliminated from monosubstituted dithiocarbamates to give isothiocyanates.53... 

TABLE 8. Complex of nitrile oxides, organic thiocyanates, isocyanates and isothiocyanates with transition metals... 

Reactions in which the a carbon possesses a carbonium ion type structure in the transition state are greatly accelerated by complexation. Ionization reactions of benzylic derivatives, i.e., the solvolysis of chlorides (Holmes et al, 1965) or the isomerization of thiocyanates or isothiocyanates (Ceccon, 1971), are accelerated by a factor of 10 -10 . This extraordinary donating effect of the Cr(CO)3 group has been interpreted either as a direct interaction of a filled metal d orbital with the empty carbon p orbital, or as metal-... 

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