Structural Conversion of Sulfur-Bridged Polynuclear Complexes by Metal Replacement Reaction

单核Co （III）配合物中的配位硫代硫原子可以与其他金属离子结合形成S桥式多核配合物。事实上，含有[Co (aet) (en) _2] ^<2+>或fac (S) - [Co (aet) _3]单元（aet=2-氨基乙硫酸酯，en=乙二胺）的S桥多核配合物的化学性质已经取得了相当大的进展。另一方面，由于用[Co (aet) _2 (en)] ^+作为起始单核配合物制备困难，长期没有对含有[Co (aet) _2 (en)] ^+单元的s桥多核配合物进行研究。我们最近发现，[Ni (aet) _2]与[CoCl_2 (en) _2] ^+的反应得到了一个S桥的CO^<III>Ni^<II> CO^<III>三核配合物[Ni {CO (aet) _2 (en)} _2] ^<4+>(1)，其中Ni^<II>原子由两个C_2-cis (S) - [CO (aet) _2 (en)] ^+的四个原子配位。为了更好地理解由八面体组成的s -桥式多核配合物的化学性质，有必要研究其他由[Co (aet) _2 (en)] ^+组成的s -桥式多核配合物。本研究发现，[Ni {Co (aet) _2 (en)} _2] Cl_4中的Ni^<II>原子是通过与水中过量的CdCl_2反应而被取代的。然而，反应产物不是相应的s桥式Co^<III>Cd^<II>Co^<III>三核配合物[Cd {Co (aet) _2 (en)} _2] ^<4+>，而是中性的双核配合物[CdCl_3 {Co (aet) _2 (en)}](2)，其中Cd原子处于三角双锥体环境。在水中用大量NaNO_3处理2时，生成阳离子Co^<III>_4Cd^<II>_2六核配合物[Cd_2Cl {Co (aet) _2 (en)} _4] ^<7+>(3)。在3中，每个Cd^<II>原子也采用三角-双锥体的几何结构，除了来自两个C_2-cis (S)- [Co (aet) _2 (en)] ^+单元的四个S原子外，还有一个Cl原子桥接。用大量NaNO_3处理水中的3，试图去除桥接Cl原子，但没有成功。因此，我们有理由认为，由C_2-cis (S) - [Co (aet) _2 (en)] ^+组成的Co^<III>Cd^<II>多核结构是由于Cd （II）对三角-双锥体的偏好而稳定的。Cd^<II>原子的大共价半径和受C_2-cis (S) - [Co (aet) _2 (en)] ^+金属配体限制的小S-Cd-S咬角似乎是造成这种几何偏好的原因。少

Coordinated thiolato S atoms in mononuclear Co (III) complexes have been recognized to bind with other metal ions to form S-bridged polynuclear complexes. In fact, considerable progress has been made in the chemistry of S-bridged polynuclear complexes containing [Co (aet) (en) _2] ^<2+> or fac (S) - [Co (aet) _3] units (aet=2-aminoethanethiolate, en=ethylenediamine). On the other hand, no S-bridged polynuclear complexes containing [Co (aet) _2 (en)] ^+ units have long been studied, because of the difficulty in preparation of [Co (aet) _2 (en)] ^+ used as a starting mononuclear complex. We have recently found that the facile reaction of [Ni (aet) _2] with [CoCl_2 (en) _2] ^+ gives an S-bridged CO^<III>Ni^<II>Co^<III> trinuclear complex, [Ni {Co (aet) _2 (en)} _2] ^<4+> (1), in which the central Ni^<II> atom is coordinated by four Satoms from two C_2-cis (S) - [Co (aet) _2 (en)] ^+ units. In order to better understand the chemistry of S-bridged polynuclear complexes composed of octahedra … More l thiolato units, it is desirable to investigate other S-bridged polynuclear complexes composed of [Co (aet) _2 (en)] ^+ units.In the present study, it was found that the replacement of the Ni^<II> atom in [Ni {Co (aet) _2 (en)} _2] Cl_4 is achieved by the reaction with excess CdCl_2 in water. However, the reaction product was not a corresponding S-bridged Co^<III>Cd^<II>Co^<III> trinuclear complex [Cd {Co (aet) _2 (en)} _2] ^<4+>, but a neutral dinuclear complex [CdCl_3 {Co (aet) _2 (en)}] (2), in which the Cd atom is situated in a trigonal-bipyramidal environment. When 2 was treated with a large amount of NaNO_3 in water, a cationic Co^<III>_4Cd^<II>_2 hexanuclear complex [Cd_2Cl {Co (aet) _2 (en)} _4] ^<7+> (3) was produced. In 3 each Cd^<II> atom also adopts a trigonal-bipyramidal geometry, coordinated by a bridging Cl atom besides four S atoms from the two C_2-cis (S)- [Co (aet) _2 (en)] ^+ units. Attempts to remove the bridging Cl atom from 3 by treating with a large amount of NaNO_3 in water were unsuccessful. Accordingly, it is reasonable to assume that the Co^<III>Cd^<II> polynuclear structures composed of C_2-cis (S) - [Co (aet) _2 (en)] ^+ units are stabilized by the preference of Cd (II) for the trigonal-bipyramidal geometry. The large covalent radius of the Cd^<II> atom and the small S-Cd-S bite angle restricted by the C_2-cis (S) - [Co (aet) _2 (en)] ^+ metalloligand seem to be responsible for this geometrical preference. Less