Novel platinum group metal complexes bearing bidentate chelating pyrimidyl-NHC and pyrimidyl imidazolyl-thione ligands: Syntheses, spectral and structural characterization

A family of novel platinum group metal complexes containing bidentate chelating 1-pyrimidyl-3-methylimidazolyl bromide (HL1·Br) and 1-pyrimidyl-3-methylimidazolyl-2-thione (L2) ligands has been synthesized. The synthetic protocol for the formation of these complexes differs from one ligand to the other. Treatment of ligand (HL1·Br) with the metal precursors led to the formation of complexes via in situ carbene transfer reactions. The silver–NHC complex (1) was formed by the reaction of HL1·Br with silver oxide under light-free conditions. Subsequent addition of appropriate metal precursors to the silver–NHC complex yielded [(η6-arene)Ru(L1)Cl]PF6 complexes {arene = C6H6 (2), p-iPrC6H4Me (3), C6Me6 (4)} on stirring at room temperature, whereas the complexes [CpRu(L1)(PPh3)]PF6 {Cp = C5H5 (5), C9H7 (6)} were obtained under reflux conditions. In the case of ligand L2, stirring of equimolar quantities of metal precursors and the ligand at room temperature yielded [(η6-arene)Ru(L2)Cl]PF6 {arene = C6H6 (7), p-iPrC6H4Me (8), C6Me6 (9)}, and [Cp∗M(L2)Cl]PF6 {Cp∗ = C5Me5, M = Rh (10), Ir (11)}. All these complexes were characterized by CHN analysis, IR, NMR and mass spectrometry besides confirmation by single crystal X-ray diffraction studies for some representative complexes as their hexafluorophosphate salts [3]PF6, [5]PF6, [8]PF6 and [10]PF6.