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.

A new series of N-heterocyclic carbene (NHC)–pyrimidine ruthenium complexes incorporating a carbene unit as an ancillary ligand were designed and successfully synthesized using simple synthetic methods.A butterfly network of complex [3]PF6 viewed along c-axis.Figure optionsDownload as PowerPoint slideHighlights
► A new series of pyrimidine-N-heterocyclic carbene (NHC) ruthenium complexes are synthesized.
► New procedure is developed to synthesize ligand pyrimidine-N-heterocyclic carbene (NHC).
► The new hard-soft nitrogen-sulfur, 1-pyrimidyl-(3-methylimidazole-2-thione) ligand was synthesized.
► Complex 3 contains butterfly network viewed along the c-axis.