Intramolecular hydrogen bonds in thiolato-, sulfenato-, and sulfinato-Co(III) complexes

The formation of intramolecular hydrogen bonds is investigated for transition metal complexes in infrared (IR) spectroscopy experiments and B3LYP/LANL2DZ computational study. Three series of complexes are considered: [Co(en)2XCH2CH2NH2]2+, [Co(en)2XCH2CH(COO)NH2]+, and [Co(en)2XCH2COO]+ (en = NH2CH2CH2NH2, XS, SO, SOO). Both experimental and theoretical results confirm the formation of the intramolecular hydrogen bond between the NH2 group of the ethylene diamine ligand and the oxygen of the COO group, as well as between the NH2 and oxygen added to coordinated sulfur. In the second and third series, the interplay between SO (or SOO) and COO results in different patterns of red‐shifted bands in model IR spectra. The relationship between strength of the intramolecular hydrogen bond and some molecular parameters (H…O distance, IR red shift, size of the quasi‐ring) is discussed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006