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

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 [H22][MeOSO3]2 and [H22][EtOSO3]2, treatment of which with base leads to neutral 2. The structure of [H22][EtOSO3]2 · H2O has been established by single crystal X-ray diffraction. The complexes [Fe(2)2][PF6]2 and [Ru(2)2][PF6]2 have been prepared and characterized, and the single crystal structure determination of [Ru(2)2][PF6]2 is reported; [Fe(2)2][PF6]2 is isostructural with [Ru(2)2][PF6]2. Treatment of [Fe(2)2]2+ with PdCl2 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 PdCl2 and [H22][MeOSO3]2 in refluxing methanol.

The salts [H22][MeOSO3]2 and [H22][EtOSO3]2 where 2 = 4′-(3,5-dimethylpyrazol-1-yl)-2,2′:6′,2″-terpyridine, have been prepared and characterized; 2 is isolated by treating these salts with base. The syntheses and structural characterizations of the complexes [Fe(2)2][PF6]2, [Ru(2)2][PF6]2 and [Pd(2)Cl][PF6] are reported; [H22][ROSO3]2 (R = Me or Et) is a more convenient precursor for complex formation than neutral ligand 2.Figure optionsDownload as PowerPoint slide