Guanidinates as chelating anionic ligands for early, middle and late transition metals: syntheses and crystal structures of [Ti{η2-(NPh)2CNEt2}2Cl2], [Ru{η2-(NPh)2CNHPh}3] and [Pt{η2-(NPh)2CNHPh}2]

Treatment of the dimeric ruthenium halide complex [Ru(η-C6H6)Cl2]2 with 1,2,3-triphenylguanidine provided the tris-chelate [Ru{η2-(NPh)2CNHPh}3] with loss of the aromatic ligand and metal oxidation. This product may also be prepared by treatment of the previously reported [Ru(η-p-PriC6H4Me){η2-(NPh)2CNHPh}Cl] with bases (KOH, LiNiPr2, NEt3). Complexes containing chelating guanidinate ligands are also available by means of metathesis of the monolithiated ligands Li[C(NR)2NR2] with metal halide complexes, as exemplified by the synthesis of the square planar bis-chelate [Pt{η2-(NPh)2CNHPh}2] from [Pt(PhCN)2Cl2] and [Ti{η2-(NPh)2CN(Et)2}2Cl2] from [TiCl4(THF)2]. The characterisation of these complexes allows a comparison of the co-ordination properties of chelating guanidinates with early, middle and late transition metals.