Platinum and palladium bis(diphenylphosphino)ferrocene (dppf) complexes with heterocyclic N-acetamide ligands: Synthesis and molecular structures of [MCl(sac)(κ2-dppf)] (M = Pt, Pd, sac = saccharinate), [PtCl(ata)(κ2-dppf)] and [Pt(ata)2(κ2-dppf)] (ataH =

Room temperature addition of sodium saccharinate, Na(sac), to [MCl2(κ2-dppf)] (M = Pd, Pt; dppf = 1,1′-bis(diphenylphosphino)ferrocene) results in the formation of [MCl(sac)(κ2-dppf)] in which the sac ligand is coordinated in a monodentate fashion through nitrogen. All attempts to coordinate a second saccharinate ligand were unsuccessful. In contrast, reaction of [PtCl2(κ2-dppf)] with N-(2-thiazolyl)acetamide (ataH) in the presence of KOH results in successive replacement of both chlorides affording [PtCl(ata)(κ2-dppf)] and [Pt(ata)2(κ2-dppf)]. Crystal structures have determined for all four complexes. In both saccharinate complexes and [PtCl(ata)(κ2-dppf)] the heterocyclic amide ligand is coordinated as expected through the amide-nitrogen. In contrast in Pt(ata)2(κ2-dppf) both ligands are bound through the nitrogen atom of the thiazole ring. In order to understand the adoption of these different ligand binding modes, geometry optimization calculations were carried out on different isomers of both ata complexes. For [PtCl(ata)(κ2-dppf)] an energy difference of 10.5 kJ mol−1 was found between observed and unobserved isomers, while for [Pt(ata)2(κ2-dppf)] the difference was 9.3 kJ mol−1. The reasons for the adoption of these different coordination modes are not clear but steric factors are likely to be a major contributory factor.

Palladium and platinum saccharinate complexes MCl(sac)(κ2-dppf) have been prepared in which sac ligand is coordinated in a monodentate fashion through nitrogen. Reaction of PtCl2(κ2-dppf) with N-(2-thiazole)acetamide (ataH) in the presence of KOH affords successively PtCl(ata)(κ2-dppf) and Pt(ata)2(κ2-dppf). In PtCl(ata)(κ2-dppf) the heterocyclic amide ligand is coordinated through the amide-nitrogen, while in Pt(ata)2(κ2-dppf) both ligands are bound through the nitrogen atom of the thiazole ring. In order to understand the adoption of these different ligand binding modes geometry optimization calculations were carried out on different isomers of both ata complexes.Figure optionsDownload as PowerPoint slideHighlights
► New palladium and platinum N-bound saccharinate complexes have been prepared.
► Platinum N-(2-thiazole)acetamide complexes have been prepared.
► Two different coordination modes of the N-(2-thiazole)acetamide ligands are seen.
► DFT calculations have been used to probe energy differences between different linkage isomers.