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

Abstract

The complexes fac-[PtXMe3(BIP)] (X Cl,Br or I;BIP 2,6-bis[1-(phenylimino)ethyl]pyridine) have been synthesised andcharacterised as involving BIP as a bidentate chelate ligand. In solution the metal-bound ligand exists in four conformationalforms, namely distal and proximal E,E and E,Z-isomers. 2D-EXSY NMR has been used to measure 1,4-metallotropic shifts ofthe PtXMe3 moiety between equivalent distal E,E forms, E,Z isomerisation of the pendant imine function and restricted C Crotation of the pendant arm of the BIP ligand. Activation energies, DG (298.15 K), for all these processes are in the range 67–96kJ mol 1 and are essentially halogen independent. A crystal structure of fac-[PtIMe3(BIP)] shows that the pendant imine functionis in the E-conformation and is rotated at an angle of 80.1° to the plane of the pyridine.