The new ligands 4Ј-nitro-2,2Ј:6Ј,2ЈЈ-terpyridine and 4Ј-prepared and the electrochemistry of the complexes has been investigated. amino-2,2Ј:6Ј,2ЈЈ-terpyridine and their homoleptic and heteroleptic iron(II) and ruthenium(II) complexes have been 2,2Ј:6Ј,2ЈЈ-Terpyridine (tpy) is a versatile ligand for com-(2) in the presence of 1 mol-% of Pd(PPh 3 ) 4 to give O 2 Ntpy (3) in 50% yield as a pale yellow microcrystalline solid plex formation with transition metals. Particular interest rests in 4Ј-substituted tpy ligands and many substituents (Scheme 1). can be directly inserted by the Kröhnke methodology [1] .
Scheme 1. a) 1 mol-% of Pd(PPh 3 ) 4 , toluene, 110°C, 16 h, 50% Some of these substituents may then be further derivatised. Some functionalised 2,2Ј:6Ј,2ЈЈ-terpyridines, such as 5,5ЈЈdimethyl-4Ј-hydroxy-2,2Ј:6Ј,2ЈЈ-terpyridine (Me 2 -HOtpy) , 4Ј-hydroxy-2,2Ј:6Ј,2ЈЈ-terpyridine (HO-tpy) and 4Ј-chloro-2,2Ј:6Ј,2ЈЈ-terpyridine (Cl-tpy), in which the functional groups are directly linked to C-4Ј, have also been reported. The placing of electron-withdrawing or electrondonating substituents in the 4Ј-position of 2,2Ј:6Ј,2ЈЈ-terpyridine alters the electronic properties of the whole ligand. This is the first example of a tpy with such a strong elec-A nitro substituent is electron-withdrawing with respect to tron-withdrawing group directly linked to C-4Ј. The withhydrogen, whilst the amino group is electron-donating.
drawing effect of this group can be observed in the deshielding of protons at C-3Ј in the 1 H-NMR spectrum, and this To the best of my knowledge, only one synthesis of a is consistent with the known σ values . The shifts of the nitrogen substituent directly attached to C-4Ј of tpy, 4Ј-disignals of protons at C-3Ј of this new tpy may be compared methylamino-2,2Ј:6Ј,2ЈЈ-terpyridine (Me 2 N-tpy), has been with two related ligands with electron-withdrawing groups reported . Dimethylamine and Cl-tpy were allowed to reat C-4Ј (Table ). act in the presence of iron(II) salts to give the iron(II) complex of Me 2 N-tpy, which was then oxidised with hydrogen