Sengar Raghvendra S, Miller Jonathan J, Basu Partha
Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15282, USA.
Dalton Trans. 2008 May 21(19):2569-77. doi: 10.1039/b714386a. Epub 2008 Mar 27.
Presence of the hydrogen bonding near a metal center can influence the properties of the complex. Here, we describe changes in redox and spectral properties in discrete dioxo-molybdenum centers coordinated by a single thiolato ligand that can support an intra-ligand hydrogen bond. We have utilized thiophenolato ligands that can harbor hydrogen bonding between the thiophenolato sulfur with an amide functionality creating either a five- or a six-membered ring. Methylation of the amide functionality removes the NH...S hydrogen bonding thus providing a basis for understanding the effect of hydrogen bonding. These thiophenolato ligands have been used in synthesizing dioxo-MoVI complexes of type Tp*MoO2(S-o-RC6H4), where R=CONHMe (), CONMe2 (), NHCOMe (), and N(Me)COMe (). The complexes have been characterized by NMR, infrared, and UV-visible spectroscopy. Spectroscopic data clearly indicate the presence of hydrogen bonding in both and , and stronger in , where hydrogen bonding stabilizes a five-membered ring. All complexes exhibit a Mo(VI)/Mo(V) redox couple and redox potentials are modulated by the nature of H-bonding. Compound with the electron-releasing N(Me)COMe group has the highest reduction potential and is more difficult to reduce.
金属中心附近氢键的存在会影响配合物的性质。在此，我们描述了由单个硫醇盐配体配位的离散二氧代钼中心的氧化还原和光谱性质的变化，该硫醇盐配体可支持配体内氢键。我们使用了苯硫酚盐配体，其在具有酰胺官能团的苯硫酚盐硫原子之间可形成氢键，从而形成五元或六元环。酰胺官能团的甲基化消除了NH...S氢键，从而为理解氢键的作用提供了基础。这些苯硫酚盐配体已用于合成Tp*MoO2(S-o-RC6H4)型的二氧代MoVI配合物，其中R = CONHMe ()、CONMe2 ()、NHCOMe ()和N(Me)COMe ()。这些配合物已通过核磁共振、红外和紫外可见光谱进行了表征。光谱数据清楚地表明和中均存在氢键，且中更强，其中氢键稳定了五元环。所有配合物均表现出Mo(VI)/Mo(V)氧化还原对，氧化还原电位受氢键性质的调节。具有供电子N(Me)COMe基团的化合物具有最高的还原电位，更难被还原。
