Insertion of Terminal and Internal Acetylenes into the Zr−μ-Methylene Bond of the Dinuclear Cationic Zirconium Complex [{Zr(η5-C5H5)}2(μ-CH2)(μ-Cl)(μ-η5-C5H4-η5-C5H4)][BMe(C6F5)3]. Synthetic Aspects, NMR Spectroscopic Study, and Dynamic Behavior in Solution

The dinuclear cationic zirconium species [{Zr(η5-C5H5)}2(μ-CH2)(μ-Cl)(μ-η5-C5H4-η5-C5H4)][BMe(C6F5)3] (1) reacts in dichloromethane at −78 °C with terminal alkynes, via insertion into the Zr−μ-methylene bond, to give various dinuclear cationic derivatives. Reaction of 1 with Me3SiC⋮CH gives the hydrido complex [{Zr(η5-C5H5)}2(μ-Cl)(μ-H)(CH2C⋮CSiMe3)(μ-η5-C5H4-η5-C5H4)][BMe(C6F5)3] (2), whereas 1-pentyne and 3,3-dimethyl-1-butyne give the μ-η1-η3-(2-alkyl)allyl derivatives [{Zr(η5-C5H5)}2(μ-Cl){μ-[η1-η3-CHC(nPr)CH2]}(μ-η5-C5H4-η5-C5H4)][BMe(C6F5)3] (3) and [{Zr(η5-C5H5)}2(μ-Cl){μ-[η1-η3-CHC(tBu)CH2]}(μ-η5-C5H4-η5-C5H4)] [BMe(C6F5)3] (4). Compounds 3 and 4 show dynamic behavior in solution involving an interchange between two enantiomeric structures through a suprafacial migration of the “−RCCH2” moiety. When compound 1 was treated with a molar equivalent of internal alkynes RC⋮CR (R = Et, nPr), formation of [{Zr(η5-C5H5)}2(μ-Cl){μ-CH2C(Et)C(Et)}(μ-η5-C5H4-η5-C5H4)][BMe(C6F5)3] (5) and [{Zr(η5-C5H5)}2(μ-Cl)...