Organometallic complexes with chiral cyclometallated ligands. The synthesis of cyclo-platinated complexes containing the (S)- or (R)-[2-NMe2C6H4CH(SiR3)](R= Me, Ph) monoanion. X-ray crystal and molecular structure of [PtCl[Ch(SiMe3)C6H4-2-NMe2](ET2S)]

Cyclometallated platinum complexes of the monoanionic ligand 2-NMe2C6H4CH(SiR3)− (R = Me, Ph; dmat-SiR3−) have been synthesized via the reaction of the organolithium reagent with both [PtCl2(Et2S)2] and [PtCl2(Et2COD] (COD = 1,5-cyclooctadiene). The 1:1 reaction of Li(dmat-SiR3) with [PtCl2(Et2S)2] affords the mono-alkylated platinum complexes [PtCl(dmat-SiR3)Et2S]. The X-ray crystal structure of one of these (R = Me) was determined. The platinum centre has a square-planar geometry with a trans-C-Pt-Cl arrangement and the chelate dmat-SiMe3 ring has a conformation that places the bulky SiMe3 substituent out of the aryl ring plane. From the 2:1 reaction of Li(dmat-SiR3) with [PtCl2(Et2S)2] no stable organoplatinum compound could be isolated. However with [PtCl2(Et2S)2COD] this 2:1 reaction affords complexes of [Pt(dmat-SiR3)2COD] stoichiometry. These latter monomeric complexes contain one cyclometallated dmat-SiR3 ligand and a COD ligand that, after having undergone an addition of the second dmat-SiR3 ligand to one of its double bonds, is η2, η1−bound to the metal.