Reactivity of Permethylzirconocene and Permethyltitanocene toward Disubstituted 1,3-Butadiynes: η4- vs η2-Complexation or C−C Coupling with the Permethyltitanocene

摘要: This paper describes the reactivity of permethylzirconocene and permethyltitanocene toward different 1,3-butadiynes. A pointed dependence on metals diyne substituents was found. Unusual, but still stable, five-membered zirconacyclocumulenes (η4-diyne complexes, zirconacyclopenta-2,3,4-trienes) Cp*2Zr(η4-1,2,3,4-RC4R), R = Ph SiMe3, were prepared using two new effective synthetic routes. One starts with bisacetylides Cp*2Zr(C⋮CR)2, (1a), SiMe3 (1b), which rearrange in sunlight to form stable (2a), (2b). The alternative route 2a 2b is reduction Cp*2ZrCl2 Mg presence adequate disubstituted butadiynes RC⋮C−C⋮CR. Both methods failed produce analogous titanacyclocumulenes, seemed extremely unstable. Nevertheless, we able obtain distinct products employing pathway permethyltitanocene. For novel tit...