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Cyclic Bis‐alkylidene Complexes of Titanium and Zirconium: Synthesis, Characterization, and Reaction
Author(s) -
Zhang Yongliang,
Wu Botao,
Zhong Mingdong,
Zhang WenXiong,
Xi Zhenfeng
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003240
Subject(s) - zirconium , titanium , cyclooctatetraene , chemistry , carbene , transition metal , cycloaddition , organometallic chemistry , metal , polymer chemistry , medicinal chemistry , catalysis , organic chemistry , molecule
Transition‐metal alkylidenes have exhibited wide applications in organometallic chemistry and synthetic organic chemistry, however, cyclic Schrock‐carbene‐like bis‐alkylidenes of group 4 metals with a four‐electron donor from an alkylidene have not been reported. Herein, the synthesis and characterization of five‐membered cyclic bis‐alkylidenes of titanium ( 4 a , b ) and zirconium ( 5 a , b ) are reported, as the first well‐defined group 4 metallacyclopentatrienes, by two‐electron reduction of their corresponding titana‐ and zirconacyclopentadienes. DFT analyses of 4 a show a four‐electron donor (σ‐donation and π‐donation) from an alkylidene carbon to the metal center. The reaction of 4 a with N , N ′‐diisopropylcarbodiimide (DIC) leads to the [2+2]‐cycloaddition product 6 . Compound 4 a reacted with CO, affording the oxycyclopentadienyl titanium complex 7 . These reactivities demonstrate the multiple metal–carbon bond character. The reactions of 4 a or 5 a with cyclooctatetraene (COT) or azobenzene afforded sandwich titanium complex 8 or diphenylhydrazine‐coordinated zirconacyclopentadiene 9 , respectively, which exhibit two‐electron reductive ability.