Crown Thioether Complexes of Low-valent Transition Metals

冠硫醚的各种低价过渡金属络合物，例如1，4，8，11-四硫杂环十四烷（[14]aneS_4）及其6，6，13，13-四甲基类似物合成了1，5，9，13-四硫杂环十六烷（[16]aneS_4）及其3，3，7，7，11，11，15，15-八甲基类似物（Me_8[16]aneS_4）。它们是RhL^+（L=R_4[14]aneS_4，R_8[16]aneS_4），顺式和反式RuCl_（L=R_4[14] aneS_4，R_8 [16]aneS_4），反式RuH（Cl）L（L=Me_4[14] aneS_4，Me_8 [16]aneS_4），反式RuH（BH_4，Ru_2H（Cl）（<nu>-H）[Me_4[14]aneS_4]_2^+，和反式MoL_2Me_8 [16]aneS_4（L '= Cl，Br，N_2，CO，<congruent>HC CH，PhC <congruent>CH，CH_2=CH_2）。这些配合物的电化学、光谱和X射线结构研究以及对模型RH（SH_2）_4）^+和trans-Mo（N_2）_2（SH_2）_4的扩展Huckel MO计算表明，冠硫醚表现为p_&lt;<pi>&gt;给体配体。通过CH_2Cl_2的简单氧化加成反应得到trans-RHCl（CH_2Cl）L^+，以及在室温条件下用PhX与trans-Mo（N_2）_2Me_8[16]aneS_4中的配位N_2分子直接芳基化反应得到trans-MoX（N_2Ph）Me_8 [16]-aneS_4（X=Br，I），进一步证实了冠硫醚的这种电子特性。研究发现，配合物的化学性质受大环的环尺寸和配合物的几何形状的影响。例如，顺式RuCl_2 R_4[14]-aneS_4与Al_2Me_6在芳烃中通过分子间C（sp^2）-H键活化反应生成反式RuCl（Ar）R_4[14]aneS_4（Ar=Ph，tolyl），而反式异构体通过类似的反应生成反式MoCl（Me）Me_4[14]aneS_4。相比之下，顺式RuCl_2 Me_8[16]aneS_4给出了预期的RuCl（Me_8[16]aneS_4。反式-Mo（N_2）_2Me_8[16]aneS_4代表了第一个只含硫配体的双氮配合物，它一直被期望作为模拟固氮酶功能的化学模型来制备。

Avariety of low-valent transition metal complexes of crown thioethers such as 1,4,8,11-tetrathia- cycloteetradecane ([14]aneS_4), its 6,6,13,13-tetramethyl analogue (Me_4[14]aneS_4), 1,5,9,13-terathiachclo-hexadecane ([16]aneS_4), and its 3,3,7,7,11,11,15,15-octamethy analogue (Me_8[16]aneS_4) have been prepared. They are RhL^+ (L=R_4[14]aneS_4, R_8[16]aneS_4), cis- and trans-RuCl_<>L (L=R_4[14]aneS_4,R_8[16]aneS_4), trans-RuH(C1)L (L=Me_4[14]aneS_4,Me_8[16]aneS_4), trans-RuH(BH_4,Ru_2H(C1)(<nu>-H) [Me_4[14]aneS_4]_2^+, and trans-MoL_2Me_8[16]aneS_4 (L'=Cl, Br, N_2, CO, HC<congruent>CH, PhC<congruent>CH, CH_2=CH_2). The elctrochemical, spectral, and x-ray structural studies of these complexes as well as extended Huckel MO calculations on the models, RH(SH_2)_4)^+ and trans-Mo(N_2)_2(SH_2)_4 revealed that the crown thioethers behave as p_<<pi>> donor ligand. this eelctronic feature of the crown thioether was further verified by the facile oxidative addition of CH_2Cl_2 to give trans-RHCl(CH_2Cl)L^+ and also by an unpercedented direct arylation of the coordinated N_2 molecule in trans-Mo(N_2)_2Me_8[16]aneS_4 with PhX under ambient conditions affording trans-MoX(N_2Ph)Me_8[16]-aneS_4 (X=Br, I). The chemical properties of the above complexes are found to be affected by the ring size of the macrocycles and the geometry of the complexes. For example, a reaction of cis-RuCl_2R_4[14]-aneS_4 with Al_2Me_6 in aromatic hydrocarbons proceeds through an intermolecular C(sp^2)-H bond activation to give trans-RuCl(Ar)R_4[14]aneS_4 (Ar=Ph, tolyl), while a similar reaction of trans-isomer afforded trans-MoCl(Me)Me_4[14]aneS_4. By contrast, cis-RuCl_2Me_8[16]aneS_4 gave an expected RuCl(Me_8[16]aneS_4. It is to be noted that trans-Mo(N_2)_2Me_8[16]aneS_4 represents the first example of dinitrogen complex containing only sulfur ligand which has been long desired to prepared as a chemical model to mimic the function of nitrogenase.