Synthesis and characterization of novel Pd(II) and Pt(II) complexes with 5-ring chelating iminoylcarbene ligands

A novel N  -iminoylimidazolium salt serves as a precursor to an iminoyl-substituted N-heterocyclic carbene ligand system with the potential to form 5-ring chelates. Reaction of 3-Me-1-[C(C6H5)N(2,6-iPr2C6H3)]C3H3N2+Cl- (3; (C–N)H+Cl−) with Ag2O leads to the silver carbene complex (C–N)AgCl 4. A crystallographic analysis of 4 reveals a monomeric (carbene)AgCl moiety with a κ1-(C) bonded iminoylcarbene ligand, in accord with NMR and IR spectroscopic data. Carbene transfer from Ag to Pd occurs upon reaction of 4 with (COD)PdCl2, resulting in the κ2-(C,N) iminoylcarbene complex (C–N)PdCl2 (5). Carbene transfer from 4 to Pt takes place with Pt2Me4(μ-SMe2)2 yielding (C–N)PtMe2 (6), which was characterized by X-ray crystallography. The monomeric Pt complex contains a 5-ring chelate with a κ2-(C,N)-bonded iminoylcarbene ligand. The Pt–Me bond distances in 6 are nearly identical (2.071(5) Å trans to carbene-C; 2.051(4) Å cis) but the 2J(195Pt–H) coupling constants are significantly different (63.1 Hz trans; 92.0 Hz cis), as are the 1J(195Pt–C) coupling constants (618 Hz trans; 799 Hz cis).

Graphical abstractPd and Pt complexes bearing a novel 5-membered iminoylcarbene chelate ring system have been prepared by carbene transfer from an Ag carbene precursor; the Ag and Pt complexes have been crystallographically characterized.Figure optionsDownload full-size imageDownload as PowerPoint slide