Structure determination and DFT studies of some new phosphite-based cycloplatinated(II) complexes containing biphosphine ligands

• The works investigates a series of monomeric and dimeric phosphite-based cycloplatinated(II) complexes.
• Dppm (bis(diphenylphosphinomethane)) and dppf (1,1′-bis(diphenylphosphino)ferrocene) act as bridging ligands between two cyclometalated parts.
• Dppe has too much tendency to produce a chelate product with cyclometalated precursor complex.
• Investigation of the nature of transition shows that that the CP cyclometalate ligand does not play a π-acceptor role.

The starting complex [PtCl{(κ2-P,C)P(OC6H4) (OPh)2}SMe2], 3, was prepared by a new method using the reaction of [PtCl2(P(OPh)3)2] with 1 equiv of PtCl2 in xylene under reflux condition followed by treatment with an excess amount of SMe2. Reaction of [PtCl{(κ2-P,C)P(OC6H4) (OPh)2}SMe2], 3, with 0.5 equiv of dppf (1,1′-bis(diphenylphosphino)ferrocene), dppm (bis(diphenylphosphinomethane)) ligands and 1 equiv of dppe ligand, PˆP, gave the dinuclear complexes [Pt2Cl2{(κ2-P,C)P(OC6H4) (OPh)2}2(μ-dppf)], 4a, [Pt2Cl2{(κ2-P,C)P(OC6H4) (OPh)2}2(μ-dppm)], 4b, and mononuclear bis-chelated [Pt{(κ2-P,C)P(OC6H4) (OPh)2}2(dppe)]Cl, 5, respectively. The complexes were fully characterized using multinuclear (1H and 31P) NMR spectroscopy and elemental analysis. The structure of typical complex 4a was further determined by X-ray crystallography. The optimized structures of the complexes in their dichloromethane solutions were obtained from DFT calculations. These optimized structures were used to determine the frontier molecular orbitals of the complexes and also the nature of their electronic transitions.

Reaction of [Pt (CˆP)Cl(SMe2)] with 0.5 or 1 equiv of a number of biphosphine ligands gave the neutral dimeric and cationic monomeric complexes. The products were fully characterized by multinuclear 1H and 31P NMR and X-ray crystallographic determination. DFT calculations were used to obtain the molecular orbitals of the complexes and also the nature of electronic transitions.Figure optionsDownload as PowerPoint slide