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

单核钴(III)配合物中的S原子与其他金属离子结合形成S桥联的多核配合物。事实上，含有[Co(Aet)(En)_2]^&lt；2&gt；或fac(S)-[Co(Aet)_3]单元的S桥联多核配合物(aet=2-氨基乙硫酸酯，en=乙二胺)的化学研究已经取得了相当大的进展。另一方面，由于作为起始单核配合物的[Co(Aet)_2(En)]^的制备难度较大，所以对含有[Co(Aet)_2(En)]^单元的S桥联多核配合物的研究还很少。我们最近发现，[Ni(Aet)_2]与[CoCl2(En)_2]^反应生成了一个S桥联的CO^&lt；III&gt；Ni^&lt；II&gt；Co^&lt；III&gt；[Ni{Co(Aet)_2(En)}_2]^&lt；4&gt；(1)，其中中心的Ni^&lt；原子由两个C_2-顺(S)-[Co(Aet)_2(En)]^单元的四个配位单元配位。为了更好地理解由八面体…组成的S桥联多核配合物的化学随着[Co(Aet)_2(En)][Co(Aet)_2(En)]和[Co(Aet)_2(En)]^单元的引入，进一步研究[Co(Aet)_2(En)]和[Co(Aet)_2(En)}]Cl4中的Ni^&lt；lt；II和gt；但反应产物不是相应的S桥联Co^&lt；III&gt；Cd^&lt；II&gt；Co^&lt；III&gt；三核配合物[Cd{Co(Aet)_2(En)_2(En)_2]^&lt；4&gt；，而是一个中性的双核配合物[Cd_3{Co(Aet)_2(En)}](2)，其中Cd原子处于三角-双锥环境中。当2在水中与大量的NaNO_3反应时，生成阳离子Co^&lt；III&gt；_4Cd^&lt；II&gt；_2六核配合物[Cd_2Cl{Co(Aet)_2(En)}_4]^&lt；7&gt；(3)。在3中，每个Cd^&lt；II&gt；原子也采用三角-双锥构型，除了两个C_2-顺(S)-[Co(Aet)_2(En)]^单元中的四个S原子外，还有一个桥联的氯原子配位。用水中大量的NaNO_3处理来去除3中的桥式氯原子的尝试失败了。因此，可以合理地假设由C_2-cis(S)-[Co(Aet)_2(En)]^单元组成的Co^&lt；III&gt；Cd^&lt；II&gt；多核结构是由于Cd(II)择优为三方双锥构型而稳定的。C_2-cis(S)-[Co(Aet)_2(En)]金属配位所限制的大的共价半径和较小的Cd-Cd-S咬合角似乎是造成这种几何择优的原因。较少

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