Protolysis of Seven-Membered Zirconacyclocumulene Complexes of Zirconocene

• Published in: Organometallics Vol. 39; no. 13; pp. 2365 - 2374
• Main Authors: Burlakov, Vladimir V, Andreev, Maxim V, Bogdanov, Vyacheslav S, Arndt, Perdita, Baumann, Wolfgang, Spannenberg, Anke, Rosenthal, Uwe, Shur, Vladimir B
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 13.07.2020; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; CHEMISTRY
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.0c00182

The interaction of the seven-membered zirconacyclocumulene complex Cp2Zr­[η4-Me3SiC4(SiMe3)–C­(C2SiMe3)=CSiMe3] (1) with an equimolar amount of HCl in dioxane at 20 °C results in the formation of the complex Cp2Zr­(Cl)–C­(CCSiMe3)C­(SiMe3)–C­(CCSiMe3)=CH­(SiMe3) (4), wherein one of the CC groups is coordinated with the Zr atom. Under similar conditions, the reaction of 1 with an excess of HCl affords Cp2ZrCl2 and a mixture cis,cis- and cis,trans-unsaturated compounds H­(Me3Si)­CC­(C2SiMe3)–C­(SiMe3)CH­(C2SiMe3) (5) and H­(Me3Si)­CC­(C2SiMe3)–C­(SiMe3)C­(H)­C2SiMe3 (6). The isomeric seven-membered zirconacyclocumulene Cp2Zr­[η4-Me3SiC4(SiMe3)–C­(SiMe3)C­(C2SiMe3)] (2) reacts with 2 equiv of HCl in dioxane to give Cp2ZrCl2, H­(Me3SiC2)­CC­(SiMe3)–C­(SiMe3)C­(C2SiMe3)H (7), and H­(Me3SiC2)­CC­(SiMe3)–C­(SiMe3)CCC­(SiMe3)H (8). The subsequent reaction of this mixture with Mg in THF yields zirconabicycles 9 and 10, respectively, containing fused zirconacyclopentadiene and cyclohexadiene rings, and, correspondingly, zirconacyclopentene and cyclopentadiene cycles. From the interaction of 7 with Cp*2ZrCl2 and Mg in THF, complex 11, analogous to 9, was isolated. The protolysis of the seven-membered zirconacyclocumulene Cp2Zr­[η4-PhC4(Ph)–(o-C6H4)] (3) with 2 equiv of HCl yields Cp2ZrCl2 and Ph2CC­(H)–CCPh (16). The structures of 4, 7, 10, and 11 have been established by X-ray crystallography. The mechanisms of the reactions found are discussed.