Low-spin iron(III) complexes with N,S coordination: syntheses, structures,and properties of bis(N-2-mercaptophenyl-2 '-pyridylmethyleniminato)iron(III) tetraphenylborate and bis(N-2-mercapto-2-methylpropyl-2 '-pyridylmethyleniminato)iron(III) tetraphenylborate

The chemistry of the iron complexes of two Schiff-base ligands namely, N-2- mercaptophenyl-2'-pyridylmethylenimine (PyASH, 1) and N-2-mercapto-2-methyl propyl-2'-pyridylmethylenimine (PyMSH, 2) has been explored in a systematic manner. Use of DMF as solvent allows one to isolate the Fe(II) complexes i n pure forms. The Fe(III) complexes [Fe(PyAS)(2)]X (X = BF4, BPh4 (3)) and [Fe(PyMS)(2)]BPh4 (4) have been synthesized via oxidation of the correspond ing Fe(II) complexes with ferrocenium salts. In 3 and 4, the deprotonated l igands are coordinated in mer fashion with two thiolato S donors cis to eac h other. The deprotonated PyAS(-) ligand frames in 3 are essentially planar due to extensive electron delocalization. The Fe(III) centers of these two complexes remain low-spin in the temperature range 8-300 K and exhibit rho mbic EPR signals with small (g(max) - g(min)) values. Results of this and o ther previously reported works suggest that tridentate Schiff-base ligands with N2S donor set (L) readily afford low-spin Fe(III) centers in [Fe-III(L )(2)](+) complexes. (C) 1999 Elsevier Science S.A. All rights reserved.