Physical and chemical properties of squarate complexes. II. Mössbauer spectroscopy and magnetic susceptibility studies of several dimeric and trimeric iron(III) complexes containing the squarate dianion

✍ Scribed by James T Wrobleski; David B Brown

• Publisher: Elsevier Science
• Year: 1979
• Tongue: English
• Weight: 814 KB
• Volume: 35
• Category: Article
• ISSN: 0020-1693
• DOI: 10.1016/s0020-1693(00)93426-1

✦ Synopsis

Products obtained by the reaction of certain bases with pdihydroxo-bis [squaratodiaquoiron(III)] dihydrate, [Fe(C404)(HZO)2(OH)] 22Hz0, I, have been isolated and studied by the complementary methods of 57Fe Miissbauer spectroscopy and magnetic susceptibility. Reaction of I with pyridine or substituted pytiine bases gives materials with formula [Fe(C.,O,,) (L)z(OH)]~~H~O where L = pyridine, I-methylpyridine, or Imethylpyridine. l%e FeZ(OHj2 bridging unit is maintained in these complexes as evidenced by their variable-tempemture magnetic susceptibility behavior. The data are very well described with a HDVV S1 = SZ = 512 dimer model where Jr -8 cm-' and g = 2.00. Dimethylsulfoxide (DMSO) reacts with I to give a p3-oxo complex containing coordinated DMSO, [Fe3O/C,O,)3(DMsO)3(H20),1 (OH). Magnetic susceptibility data for this complex are analyzed with a HDVV S1 = S2 = S3 = 5f2 trimer model by assuming equivalen t spin sites. Results of this analysis give J = -39 cm-' and g = 2.00. The proposed trimeric structure of this complex is also inferred from the presence of a strong infrared absorption near 550 cm-l assigned to the Fe-O stretching mode, v,,,(Fe30). Reaction of I with KOH in

ethanol yields a material whose magnetic susceptibility versus tempemture behavior is indicative of a S1 = S2 = 512 dimer with J = -96 cm-' and g = 2.00. Presence of a strong infrared absorption at 820 and 7.50 cm-', assigned to the Fe-O-Fe stretching mode, v,,,(Fe2-0) is additional evidence for the proposed p-oxo structure for this complex, [Fe(C404)(H20),] 20. Miissbauer spectral parameters for these fem'csquarate complexes are consistent with proposed structures.