Probing the ‘Venus fly-trap’ parameters of cyclo-octadiene in selected β-diketonato complexes of platinum(II) and the nickel-triad from a spectroscopic, X-ray crystallographic and DFT study

Synthetic, structural and theoretical studies of Pt(II) complexes of a series of β-diketonato ligands with a variation of sterics, namely acetylacetonato (acac) and thenyoltrifluoroactonato (thtfac), are reported. The crystal structures of [Pt(cod)(acac)]PF6(I), [Pt(cod)(acac)]BF4(II) and [Pt(cod)(thtfac)]BF4(III) are presented while the complexes were characterized spectroscopically by IR, 1H and 13C NMR spectroscopy. DFT calculations of the group 10 transition metals in the nickel triad, utilising the model complex, [M(cod)(acac)]+, to gain further insights in the variation of the transition metal within the complex and the interactions with both the β-diketonato and cis,cis-1,5-cyclo-octadiene (cod) co-ordinating ligands are reported. In particular, the variation in the ‘Venus fly-trap’ bite and jaw dihedral angles, χ and ψ, is ca. 2° and 4°, respectively, and therefore quite small, but significant. The HOMO and LUMO energy gaps between the Ni(II) and Pd(II) complexes were insignificant, while that of Pt(II) is >1 eV higher than the corresponding 3rd and 4th row congener complexes.

Single crystal structures of platinum(II) 1,5-cyclo-octadiene (cod) complexes are reported, describing solid state packing modes, bond distances, hydrogen bonds, metal chelate ring and halogen interactions, while a correlation with DFT optimised structures of the nickel triad is presented, evaluating comparative properties and in particular the geometry (ψ angle) of the cod ligand as a ‘Venus fly-trap’ mimic.Figure optionsDownload as PowerPoint slide