Gómez-Iglesias Patricia, Arroyo Marta, Bajo Sonia, Strohmann Carsten, Miguel Daniel, Villafañe Fernando
GIR MIOMeT-IU Cinquima-Química Inorgánica, Facultad de Ciencias, Campus Miguel Delibes, Universidad de Valladolid , 47011 Valladolid, Spain.
Inorg Chem. 2014 Dec 1;53(23):12437-48. doi: 10.1021/ic5018054. Epub 2014 Nov 7.
Mixed pyrazole-acetonitrile complexes, both neutral fac-[ReBr(CO)3(NCMe)(pzH)] (pzH = pzH, pyrazole; dmpzH, 3,5-dimethylpyrazole; or indzH, indazole) and cationic fac-[Re(CO)3(NCMe)(pzH)2]A (A = BF4, ClO4, or OTf), are described. Their role as the only starting products to obtain final pyrazolylamidino complexes fac-[ReBr(CO)3(NH═C(Me)pz-κ(2)N,N)] and fac-[Re(CO)3(pzH)(NH═C(Me)pz-κ(2)N,N)]A, respectively, is examined. Other products involved in the processes, such as fac-[ReBr(CO)3(pzH)2], fac-[Re(CO)3(NCMe)(NH═C(Me)pz-κ(2)N,N)]A, and fac-[Re(CO)3(pzH)2(OTf)] are also described. Warming CD3CN solutions of fac-[Re(CO)3(NCMe)(pzH)2]A at 40 °C gives cleanly the pyrazolylamidino complexes [Re(CO)3(pzH)(NH═C(Me)pz-κ(2)N,N)]A as the only products, pointing to an intramolecular process. This is confirmed by carrying out reactions in the presence of one equivalent of a pyrazole different from that coordinated, which affords complexes where the pyrazolylamidino ligand contains only the pyrazole previously coordinated. When the reactions lead to an equilibrium mixture of the final and starting products, the reverse reaction gives the same equilibrium mixture, which indicates that the coupling reaction of pyrazoles and nitriles to obtain pyrazolylamidino ligands is a reversible intramolecular process. A systematic study of the possible factors which may affect the reaction gives the following results: (a) the yields of the direct reactions are higher for lower temperatures; (b) the tendency of the pyrazoles to give pyrazolylamidino complexes follows the sequence indzH > pzH > dmpzH; and (c) the reaction rates do not depend on the nature of the anion even when a large excess is added. The presence of a small amount of aqueous solution of NaOH catalyzes the reaction. Thus, addition of 0.5-1% of NaOH (aq) to solutions of fac-[ReBr(CO)3(NCMe)(pzH)] (in CD3CN) or fac-[Re(CO)3(NCMe)(pzH)2]A (in CD3CN, CD3NO2 or (CD3)2CO) allowed the syntheses of the corresponding pyrazolylamidino complexes [ReBr(CO)3(NH═C(Me)pz*-κ(2)N,N)] or [Re(CO)3(pzH)(NH═C(Me)pz-κ(2)N,N)]A with better yields, more rapidly, and in milder conditions.
本文描述了混合吡唑 - 乙腈配合物，包括中性的面式 - [ReBr(CO)₃(NCMe)(pzH)]（pzH = pzH，吡唑；dmpzH，3,5 - 二甲基吡唑；或indzH，吲唑）和阳离子面式 - [Re(CO)₃(NCMe)(pzH)₂]A（A = BF₄、ClO₄或OTf）。研究了它们分别作为获得最终吡唑基脒配合物面式 - [ReBr(CO)₃(NH═C(Me)pz - κ(2)N,N)]和面式 - [Re(CO)₃(pzH)(NH═C(Me)pz - κ(2)N,N)]A的唯一起始产物的作用。还描述了该过程中涉及的其他产物，如面式 - [ReBr(CO)₃(pzH)₂]、面式 - [Re(CO)₃(NCMe)(NH═C(Me)pz - κ(2)N,N)]A和面式 - [Re(CO)₃(pzH)₂(OTf)]。在40℃加热面式 - [Re(CO)₃(NCMe)(pzH)₂]A的CD₃CN溶液，可干净地得到吡唑基脒配合物[Re(CO)₃(pzH)(NH═C(Me)pz - κ(2)N,N)]A作为唯一产物，表明这是一个分子内过程。在存在一当量不同于配位吡唑的吡唑的情况下进行反应，证实了这一点，该反应得到的配合物中吡唑基脒配体仅包含先前配位的吡唑。当反应导致最终产物和起始产物的平衡混合物时，逆反应给出相同的平衡混合物，这表明吡唑与腈的偶联反应以获得吡唑基脒配体是一个可逆的分子内过程。对可能影响反应的因素进行的系统研究给出了以下结果：(a) 较低温度下直接反应的产率更高；(b) 吡唑生成吡唑基脒配合物的倾向遵循indzH > pzH > dmpzH的顺序；(c) 即使加入大量过量的阴离子，反应速率也不取决于阴离子的性质。少量NaOH水溶液的存在催化了反应。因此，向面式 - [ReBr(CO)₃(NCMe)(pzH)]（在CD₃CN中）或面式 - [Re(CO)₃(NCMe)(pzH)₂]A（在CD₃CN、CD₃NO₂或(CD₃)₂CO中）的溶液中加入0.5 - 1%的NaOH（水溶液），能够在更温和的条件下更快地合成相应的吡唑基脒配合物[ReBr(CO)₃(NH═C(Me)pz* - κ(2)N,N)]或[Re(CO)₃(pzH)(NH═C(Me)pz - κ(2)N,N)]A，且产率更高。
