Assignment of the E , Z configurational isomers of platinum complexes of N , N ‐dialkyl‐ N ′ ‐acyl(aroyl)thioureas by means of triple resonance 1 H/ 13 C/ 195 Pt PFG correlation NMR spectroscopy

Unsymmetrical, dialkyl‐substituted N , N ‐dialkyl‐ N ′ ‐acyl(aroyl)thioureas show E , Z configurational isomerism at room temperature in solution, which is also expressed in the existence of cis ‐[Pt( ZZ ‐L‐ S , O ) 2 ], cis ‐[Pt( EZ ‐L‐ S , O ) 2 ] and cis ‐[Pt( EE ‐L‐ S , O ) 2 ] complexes derived from these ligands. These configurational isomers were assigned by means of a double magnetization transfer 1 H/ 13 C/ 195 Pt correlation NMR experiment, despite the fact that the long‐range 5 J ( 195 Pt, 1 H) and 4 J ( 195 Pt, 13 C) scalar couplings are not directly observable in their 1 H and 13 C spectra at high field. Depending on the ligand structure, the relative amounts of cis ‐[Pt( ZZ ‐L‐ S , O ) 2 ], cis ‐[Pt( EZ ‐L‐ S , O ) 2 ] and cis ‐[Pt( EE ‐L‐ S , O ) 2 ] complexes are in the ranges 40–42% ZZ , 46–47% ZE and 12–13% EE . The cis ‐bis[ N ‐methyl‐ N ‐( tert ‐butyl)‐ N ′ ‐(2,2‐dimethylpropanoyl)thioureato]platinum(II) complex is found to occur exclusively as the ZZ isomer. Copyright © 2003 John Wiley & Sons, Ltd.