Synthesis and Isolation of Di-n-butylhafnocene and Its Application as a Versatile Starting Material for the Synthesis of New Hafnacycles

• Published in: Organometallics 2009-05, Vol.28 (9), p.2864-2870
• Main Authors: Burlakov, Vladimir V, Beweries, Torsten, Bogdanov, Vyacheslav S, Arndt, Perdita, Baumann, Wolfgang, Petrovskii, Pavel V, Spannenberg, Anke, Lyssenko, Konstantin A, Shur, Vladimir B, Rosenthal, Uwe
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om900122w

The previously described hafnocene alkyne complexes are of limited applicability for the generation of the hafnocene fragment in stoichiometric and catalytic reactions. For this reason di-n-butylhafnocene (1-Hf) was fully characterized and used as a hafnocene source in reactions with alkynes and diynes. With bis(trimethylsilyl)acetylene and pyridine the alkyne complex Cp2Hf(py)(η2-Me3SiC2SiMe3) (2-Hf) was obtained and coordination of di-tert-butylbutadiyne yielded the first structurally characterized hafnacyclocumulene, Cp2Hf(η4-t-BuC4-t-Bu) (4-Hf). By the coupling of 2 equiv of the 1,3-butadiyne RC4R at the hafnocene center, hafnacyclopentadienes were formed regioselectively (R = t-Bu, 5- t -Bu-Hf; R = SiMe3, 5-SiMe 3 -Hf). In the case of 1,4-diphenylbutadiyne the hafnocene-substituted [4]radialene 6-Hf was formed. Treatment of the latter with acid gave the free [4]radialene 7. In the reaction of 4-Hf with diphenylacetylene, the alkyne inserted into the Hf−Cα bond to give the hafnacyclopentadiene 8.