Cyclic Bis‐alkylidene Complexes of Titanium and Zirconium: Synthesis, Characterization, and Reaction. Issue 69 (27th October 2020)

• Record Type: Journal Article
• Authors: Zhang, Yongliang; Wu, Botao; Zhong, Mingdong; Zhang, Wen‐Xiong; Xi, Zhenfeng
• Is Part Of: Chemistry. Volume 26:Issue 69(2020)
• Page Start: 16472
• Page End: 16479
• Publication Date: 2020-10-27
• Subjects: alkylidenes -- cyclic bis-carbene complexes -- group 4 metals -- metallacycles -- metallacyclopentatriene; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202003240
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: 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. Abstract : In for a Schrock : The synthesis and characterization of five‐membered cyclic Schrock‐carbene‐like bis‐alkylidenes of titanium and zirconium are realized. These Schrock‐carbene‐like bis‐alkylidenes show unique reactivity toward N, N ′‐diisopropylcarbodiimide, CO, cyclooctatetraene, and azobenzene.