Multiple bonding modes exhibited by heteroscorpionate N2S(alkylthiolate) ligands with Zn(II) and Fe(II)

• DOI: 10.1016/j.poly.2003.11.034
• Publication Date: 2004-01-20T05:19:34Z
• Authors: Vivek V Karambelkar; Robert C diTargiani; Christopher D Inc...; Lev N Zakharov; Arnold L Rheingold; Charlotte L Stern; David P Goldberg
• Keywords: 01 natural sciences; 0104 chemical sciences

Abstract Two related heteroscorpionate N2S(thiolate) ligands L1 and L2 have been employed in the synthesis of new zinc(II) and iron(II) complexes. These ligands contain two imidazolyl donors and one alkylthiolate donor connected by a central carbon atom. The ligand L1 was reacted with ZnBr2 to give the trinuclear zinc complex [(L1)3Zn3Br2]Br (1). The X-ray structure of 1 reveals one of the zinc ions to be coordinated by two L1 ligands in a tripodal arrangement resulting in a distorted octahedral geometry, while the other two zinc ions are both held in a distorted tetrahedral geometry and are coordinated to another molecule of L1 in an unusual tridentate, multibridging coordination mode. Modification of L1 to include phenyl substituents on the imidazole groups leads to L2, and these substituents cause quite a different result to be obtained in the reaction with ZnBr2. The combination of L2 and ZnBr2 leads to the dimeric zinc complex (L2)2Zn2Br2, (2). Characterization of 2 by X-ray diffraction shows this complex to be a dimer with a central Zn2(μ-SR)2 rhomb. Each zinc ion is found in a distorted tetrahedral geometry coordinated by L2 in a bidentate, N,S fashion. The 1H NMR spectrum of 2 provides strong evidence this structure is retained in solution. In comparison, reaction of L2 with FeCl2 leads to the monomeric complex (L2)2FeII (3), which has each ligand coordinated in the same bidentate, N,S bonding mode. Interestingly, the methoxy groups of the two ligands in 3 are close enough to the iron center for a possible bonding interaction, suggesting an unexpected N2O coordination mode.