A pyrazolyl-terminated 2,2′:6′,2″-terpyridine ligand: Iron(II), ruthenium(II) and palladium(II) complexes of 4′-(3,5-dimethylpyrazol-1-yl)-2,2′:6′,2″-terpyridine

Abstract

The preparation of 4′-(3,5-dimethylpyrazol-1-yl)-2,2′:6′,2″-terpyridine ( 2) under acidic conditions results in the formation of the salts [H 2 2][MeOSO 3] 2 and [H 2 2][EtOSO 3] 2, treatment of which with base leads to neutral 2. The structure of [H 2 2][EtOSO 3] 2 · H 2O has been established by single crystal X-ray diffraction. The complexes [Fe( 2) 2][PF 6] 2 and [Ru( 2) 2][PF 6] 2 have been prepared and characterized, and the single crystal structure determination of [Ru( 2) 2][PF 6] 2 is reported; [Fe( 2) 2][PF 6] 2 is isostructural with [Ru( 2) 2][PF 6] 2. Treatment of [Fe( 2) 2] 2+ with PdCl 2 produces [Pd( 2)Cl] +, isolated and structurally characterized as the hexafluoridophosphate salt, illustrating that metal exchange within the tpy-binding domain occurs in preference to palladium(II) coordination by the N-donor atom of the pendant 3,5-dimethylpyrazol-1-yl unit in 2. [Pd( 2)Cl] 2+ can also be prepared from PdCl 2 and [H 2 2][MeOSO 3] 2 in refluxing methanol.