Migratory Insertion of an Isocyanide into 1-Zirconacyclopent-3-ynes

The reactions of the 1-zirconacyclopent-3-ynes Cp‘2Zr(η4-H2C4H2) with Cp‘2 = Cp2 (1), (η5-t-Bu-C5H4)2 (2), and Me2Si(η5-C5H4)2 (3) and of the zirconacyclopropene Me2Si(η5-C5H4)2Zr(THF)(η2-Me3SiC2SiMe3) (8) toward t-Bu-NC are described. In the case of the 1-zirconacyclopent-3-ynes 2 equiv of
t-Bu-NC were inserted into the β-Zr−C bonds of the zirconacycle. After subsequent rearrangement the
substituted 1-zircona-2,5-diazacyclopent-3-enes 4, 5, and 6, possessing an anellated cyclobutene ring
having two exocyclic double bonds, were obtained. In the protolysis of 6 with MeOH the metal-free
cyclobutene 7 was formed. The alkyne complex 9 reacted with the isocyanide to give end-on complexation
instead of an expected insertion, resulting in the alkyne complex Me2Si(η5-C5H4)2Zr(η1-CN-t-Bu)(η2-Me3SiC2SiMe3) (11).

本研究详述了1-锆杂环戊-3-炔（1-zirconacyclopent-3-ynes）类化合物Cp'₂Zr(η⁴-H₂C₄H₂)（其中Cp'₂分别为Cp₂（1，Cp为环戊二烯基cyclopentadienyl）、(η⁵-叔丁基环戊二烯基)₂（2）以及二甲基硅基桥联二(η⁵-环戊二烯基)（3）），以及锆杂环丙烯（zirconacyclopropene）类化合物Me₂Si(η⁵-C₅H₄)₂Zr(四氢呋喃(THF, tetrahydrofuran))(η²-1,2-双(三甲基硅基)乙炔)（8）与叔丁基异氰（t-Bu-NC, tert-butyl isocyanide）的反应。针对1-锆杂环戊-3-炔类底物，2当量的叔丁基异氰插入至锆杂环的β-Zr-C键中；经后续重排后，得到带有双环外双键的稠合环丁烯结构的取代1-锆杂-2,5-二氮杂环戊-3-烯（1-zircona-2,5-diazacyclopent-3-enes，4、5、6）。将化合物6以甲醇（MeOH, methyl alcohol）进行质子解反应，可得到不含金属的环丁烯产物7。而炔烃配合物9与叔丁基异氰反应时，并未发生预期的插入反应，而是发生端基配位，最终生成炔烃配合物Me₂Si(η⁵-C₅H₄)₂Zr(η¹-叔丁基异氰基)(η²-1,2-双(三甲基硅基)乙炔)（11）。