Tetrakis(trialkylsilylethynyl)butatriene and 1,1,4,4‐Tetrakis(trialkylsilylethynyl)‐1,3‐butadiene: Novel Cross‐Conjugated Chromophores
Tetrakis(trialkylsilylethynyl)butatriene and 1,1,4,4‐Tetrakis(trialkylsilylethynyl)‐1,3‐butadiene: Novel Cross‐Conjugated Chromophores
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四(三烷基甲硅烷基乙炔基)丁三烯和1,1,4,4-四(三烷基甲硅烷基乙炔基)-1,3-丁二烯：新型交叉共轭发色团
DOI：
10.1002/anie.199311871
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发表时间：
1993
影响因子：
--
通讯作者：
F. Diederich
中科院分区：
文献类型：
--
作者：
J. V. Loon;P. Seiler;F. Diederich
观察结果支持了在 D、O 存在下 3b 的还原仅产生二氘代丁二烯 7b。以前，仅描述了活化烯烃 HRC= CRH (R= CO, Me, COPh)，['3a1 以及 7, 7, 8, 8-四氰基醌甲烷 (TCNQ) 和四氰基乙烯 (TCNE) 的双键还原。''3b1 我们认为 3b 容易发生还原，因为 a) 具有 sp 碳原子的两个二乙炔亚甲基片段发挥了激活中心双键的吸电子效应，从而促进 PPh 的攻击，b) 这些片段有助于通过阴离子电荷的离域来稳定所得的两性离子！ 14] 因此，1, 4-双（五亚甲基）-1, 2, 3-b~-tatriener6I 没有被充分激活以被 PPh 还原，已知铑@) 可以与丁三烯" 51 和炔烃形成稳定的'1''复合物，[16] 并且我们有兴趣确定是否与 3b 发生区域选择性络合，其具有两种类型的 K 系统。当 3b 是在 20" C 下，用一当量的 [Rh (PPh,), Cl] 在 CH、Cl 中处理，得到络合物 8（熔点 202-203" C），为橙黄色固体，产率为 57%。 在该转化中，丁二烯 7a 始终作为副产物以 40% 的产率分离，可能是由于 3b 与一当量的 PPh 反应，PPh 在形成过程中释放出来。 8. 8在CDCl中的1H NMR谱显示了TIPS基团质子的复杂模式，这可能是由于络合物中的空间位阻导致这些基团的旋转受阻。 I3C NMR 谱显示在 6= 108.4 和 104.3 (Si-CGC) 以及 93.6 和 92.7 (Si-CC) 处有两组炔属碳，这表明由中心累积键络合产生的对称结构。由于与铑和磷的偶联，两个金属环碳原子在 6= 146.7 处表现出多重态。对丙酮溶液中生长的晶体进行低温X射线分析，明确证明了8中丁三烯单元中心双键的选择性络合。['* l 该化合物在空间群Pi中结晶，不对称单元包含两个独立的分子，其中分子1如图3所示。2.00 f 0.01 A的Rh-C键长在之前发现的范围内。累积烯-铑配合物。['51 金属环中的 CC 键 (1.35 A) 比 3b 中的 C= C 键 (1.25 A) 长得多，这反映了由于与铑配位而导致的较低键级。两个PPh配体轴向配位； I3C NMR 谱中 C (pheny1)-P 耦合常数的分析也为溶液络合物中膦的反式配位提供了支持。由四乙炔基累积烯碳原子、铑和氯原子组成的络合物中心框架的几何形状在分子 1（图 3 B）和 2 中大致呈平面（在 0.34 A 以内）。
supported by the observation that reduction of 3b in the presence of D, O affords exclusively the dideuterated butadiene 7 b. Previously, the reduction of double bonds with phosphanes had only been described for activated olefins HRC= CRH (R= CO, Me, COPh),['3a1 and for 7, 7, 8, 8-tetracyanoquinomethane (TCNQ) and tetracyanoethylene (TCNE).''3b1 We propose that facile reduction of 3b occurs, since a) the two diethynylmethylene fragments with their sp carbon atoms exert an activating, electron-withdrawing effect on the central double bond, therefore facilitating the attack of PPh,, and b) these fragments help to stabilize the resulting zwitterion through delocalization of the anionic charge! 14] Accordingly, 1, 4-bis (pentamethylene)-l, 2, 3-b~-tatriener6I is not sufficiently activated to be reduced with PPh,.Rhodium@) is known to form stable'1''complexes with both butatrienes" 51 and alkynes,[16] and we were interested to determine whether regioselective complexation occurs with 3b, which features both types of K systems. When 3b was treated at 20" C with one equivalent of [Rh (PPh,), Cl] in CH, CI,, complex 8 (mp 202-203" C) was obtained in 57% yield as an orange-yellow solid."'In this conversion, butadiene 7a was consistently isolated as a by-product in 40% yield, presumably due to the reaction of 3b with the one equivalent of PPh, that is liberated during the formation of 8. The'H NMR spectrum of 8 in CDCl, shows a complex pattern for protons of the TIPS group, presumably due to hindered rotation of these groups as a result of steric hindrance in the complex. The I3C NMR spectrum shows two sets of acetylenic carbons at 6= 108.4 and 104.3 (Si-CGC) and at 93.6 and 92.7 (Si-CC), which is indicative of the symmetrical structure resulting from complexation at the central cumulenic bond. The two metallacyclic carbon atoms exhibit a multiplet at 6= 146.7 due to coupling to both rhodium as well as phosphorous. Unambiguous proof for the selective complexation at the central double bond of the butatriene unit in 8 was provided by the low-temperature X-ray analysis on crystals grown from acetone solution.['* l The compound crystallizes in the space group Pi, and the asymmetric unit contains two independent molecules of which molecule 1 is shown in Figure 3. The Rh-C bond lengths of 2.00 f 0.01 A are within the range of those previously found in cumulene-rhodium complexes.['51 The CC bond in the metallacycle (1.35 A) is considerably longer than the C= C bond in 3b (1.25 A), which reflects the lower bond order due to the coordination with the rhodium. The two PPh, ligands are axially coordinated; the analysis of the C (pheny1)-P coupling constants in the I3C NMR spectrum also provides support for trans coordination of the phosphanes in the solution complex. The geometry of the central framework of the complex, consisting of the tetraethynylcumulene carbon atoms, the rhodium, and the chlorine atoms, is roughly planar (within 0.34 A) in both molecules 1 (Fig. 3 B) and 2. However, the