Stereochemically non-rigid transition metal complexes of 2,6-bis[1-(phenylimino)ethyl]pyridine (BIP). Part 3. Dynamic NMR studies of fac-[PtXMe 3(BIP)] (X=C1, Br, or I). Crystal structure of fac-[PtIMe 3(BIP)

Abstract

The complexes fac-[PtXMe 3(BIP)] (X=Cl,Br or I;BIP=2,6-bis[1-(phenylimino)ethyl]pyridine) have been synthesised and characterised as involving BIP as a bidentate chelate ligand. In solution the metal-bound ligand exists in four conformational forms, namely distal and proximal E,E and E,Z-isomers. 2D-EXSY NMR has been used to measure 1,4-metallotropic shifts of the PtXMe 3 moiety between equivalent distal E,E forms, E,Z isomerisation of the pendant imine function and restricted CC rotation of the pendant arm of the BIP ligand. Activation energies, Δ G ≠ (298.15 K), for all these processes are in the range 67–96 kJ mol −1 and are essentially halogen independent. A crystal structure of fac-[PtIMe 3(BIP)] shows that the pendant imine function is in the E-conformation and is rotated at an angle of 80.1° to the plane of the pyridine.