Reactions of halogens with Pt(II) complexes of N-alkyl- and N,N-dialkyl-Nʹ -benzoylthioureas: oxidative addition and formation of an I₂ inclusion compound

The treatment of cis-[PtII(L1a/b-S,O)2] complexes of N,N-diethyl- (HL1a) and N,N-di(n-butyl)-N'-benzoylthiourea (HL1b) with I2 or Br2 in chloroform, leads to rapid oxidative addition to yield several geometric isomers of [PtIV(L-S,O)2X2] (X = I, Br); the reactions can be monitored by 195Pt NMR and UV-visible spectrophotometry. The products cis-[PtIV(L1a-S,O)2I2] 6 and cis-[PtIV(L1a-S,O)2Br2] 7, which have been isolated and structurally characterized, are the first-reported crystal structures of complexes of Pt(IV) with this class of ligand. Molecules of 6 pack such that the I–Pt–I axes are essentially aligned, with unusually close nearest-neighbour iodide contacts (3.553(1) A˚ ). These short I···I intermolecular interactions lead to infinite chains of weakly connected molecules in crystals of the compound. No such interactions are evident in the corresponding crystals of 7. Reaction of the Pt(II) complex of N-propyl-N'-benzoylthiourea (H2L2a) cis-/trans-[PtII(H2L2a-S)2Br2] with Br2 also results in oxidative addition, to yield trans-PtIV(H2L2a-S)2Br4 9. By contrast, treatment of cis-/trans-[PtII(H2L2a-S)2I2] with I2 does not lead to an oxidative addition product, yielding instead an interesting iodine inclusion compound of PtII, trans-[PtII(H2L2a-S)2I2]·I2 8. In 8, short intermolecular I···I distances of 3.453(1) A˚ between I2 and coordinated iodide ions in trans-[PtII(H2L2a-S)2I2] molecules, result in infinite chains of weakly linked trans-[PtII(H2L2a-S)2I2] ···I2 groups in the lattice. However, the empirically estimated bond order of 0.75 for the included I2 molecules does not support the possible existence of discrete tetraiodide ions (I42−) in the lattice of compound 8