Coordination Chemistry of the Parent Dithiocarbamate H 2 NCS 2 - : Organometallic Chemistry and Tris-Chelates of Group 9 Metals.

Two tris-chelate complexes of cobalt and rhodium and two complexes of Ru(II) of dithiocarbamate, [S 2 CNH 2 ] - , were synthesized. The complexes were spectroscopically characterized by IR, NMR, UV-vis, and MS and structurally characterized by X-ray diffraction. The structural features of the rhodium complex were compared to those of other tris-chelate Rh(III) dithiocarbamate complexes and are characterized by a change in the ground-state geometry in comparison to expected octahedral tris-chelate complexes. This was confirmed both experimentally by X-ray diffraction and theoretically using DFT calculations. The inversion barriers of Rh(Bz 2 dtc) 3 , Ir(Bz 2 dtc) 3 , and Rh(Et 2 dtc) 3 were determined using VT-NMR in DMSO. These barriers were found to be surprisingly low for heavy group 9 elements of d 6 tris-chelate complexes: values of 16.7, 17.1, and 16.4 kcal/mol were calculated, respectively. By comparing structural features, we are able to determine that the activation barrier for the inversion of stereochemistry of Rh(H 2 dtc) 3 must have a similarly low value. A modified version of the Bailar twist involving an intermediate with C 3 h geometry was proposed as the mechanism of inversion.