UNIQUE REACTIVITY CHARACTERISTICS OF MO-COORDINATED S-2(2-) AND S-4(2-) LIGANDS
UNIQUE REACTIVITY CHARACTERISTICS OF MO-COORDINATED S-2(2-) AND S-4(2-) LIGANDS
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DOI：
10.1016/s0277-5387(00)84932-3
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发表时间：
1986-01-01
期刊：
影响因子：
2.6
通讯作者：
ILEPERUMA, O
中科院分区：
文献类型：
--
作者：
COUCOUVANIS, D;HADJIKYRIACOU, A;ILEPERUMA, O
报道了新的二硫杂环戊烯配合物[{(MeOOC)2C2S2}2Mo(μ2-S)]−2和[OMo(S2C2(Coome)2)2]−的合成。它们分别与[(S4)Mo(S)(μ2-S)2Mo(S)(S4)]2−或[(CS4)Mo(S)(μ2-S)2Mo(S)(CS4)]2−和[OMo(S4)2]2−反应得到。[(S4)Mo(O)(μ2-S)2Mo(O)(S2)]2−与二甲基甲胺反应生成了新的二硫烯配合物[{(MeOOC)2C2S2}Mo(O)(μ2-S)]−2，它是[(S2)Mo(O)(μ2-S)2Mo(O)(S2)]2−与二甲基甲酰胺反应生成的乙烯基二硫醚配合物的异构体。含有相同[Mo2O2S2]2+核的两个配合物之间的反应性差异归因于S2−4和S2−2配体本质上不同的反应特性。作为Mo-SDπ-pπ成键的结果，在几乎所有结构表征的Mo-S4单元中观察到SS键长的交替。与MoS键相邻的SS键的减弱使得S02容易从Mo配位的S2−4配体上解离出来。这种弱化也解释了在炔烃与Mo-S4单元的环加成反应中容易形成二硫烯的原因。相比之下，在Mo配位的S22配体中，由于配体−*-轨道的布居减少而加强了SπS键。后者与炔烃的反应不通过环加成进行。相反，至少有一个这样的反应被报道插入到MoO键中。讨论了活性多硫化物配体在加氢脱硫反应中的重要性。
The synthesis of the new dithiolene complexes, [{(MeOOC)2C2S2}2Mo(μ2-S)]−2and [OMo(S2C2(COOMe)2)2]−, is reported. These complexes are obtained by the reaction of dicarbomethoxyacetylene (DMA) with either [(S4)Mo(S)(μ2-S)2Mo(S)(S4)]2−or [(CS4)Mo(S)(μ2-S)2Mo(S)(CS4)]2−and [OMo(S4)2]2−, respectively. The reaction of [(S4)Mo(O)(μ2-S)2Mo(O)(S2)]2−with DMA results in the new dithiolene complex [{(MeOOC)2C2S2}Mo(O)(μ2-S)]−2, which is the isomeric form of the vinyl disulfide complex obtained in the reaction of the [(S2)Mo(O)(μ2-S)2Mo(O)(S2)]2−complex with DMA. The difference in reactivity between the two complexes that contain the same [Mo2O2S2]2+core is attributed to the intrinsically different reactivity characteristics of the S2−4and S2−2ligands. As a result of Mo-Sdπ-pπbonding an alternation in the SS bond lengths is observed in virtually all of the structurally characterized Mo-S4units. The consequent weakening of the SS bonds adjacent to the MoS bonds allows for the ready dissociation of S02from the Mo-coordinated S2−4ligands. This weakening also accounts for the facile formation of dithiolenes in cycloaddition reactions of alkynes with the Mo-S4units. By comparison, the SS bond in side-on Mo-coordinated S2−2ligands is strengthened as a result of depopulation of the ligand π*-orbitals. Reactions of the latter with alkynes do not proceed by cycloaddition. Instead, insertion into the MoO bond has been reported for at least one such reaction. The importance of activated polysulfide ligands in the hydrodesulfurization reaction is discussed.