849926-75-6Relevant articles and documents
Zinc-zinc bonded zincocene structures. Synthesis and characterization of Zn2(η5-C5Me5)2 and Zn2(η5-C5Me4Et)2
Grirrane, Abdessamad,Resa, Irene,Rodriguez, Amor,Carmona, Ernesto,Alvarez, Eleuterio,Gutierrez-Puebla, Enrique,Monge, Angeles,Galindo, Agustin,Del Rio, Diego,Andersen, Richard A.
, p. 693 - 703 (2007/10/03)
While, in general, decamethylzincocene, Zn(C5Me 5)2, and other zincocenes, Zn(C5Me 4R)2 (R = H, But, SiMe3), react with dialkyl and diaryl derivatives, ZnR′2, to give the half-sandwich compounds (η5-C5Me4R) ZnR′, under certain conditions the reactions of Zn(C5Me 5)2 with ZnEt2 or ZnPh2 produce unexpectedly the dizincocene Zn2(η5-C 5Me5)2 (1) in low yields, most likely as a result of the coupling of two (η5-C5Me 5)Zn. radicals. An improved, large scale (ca. 2 g) synthesis of 1 has been achieved by reduction of equimolar mixtures of Zn(C 5Me5)2 and ZnCl2 with KH in tetrahydrofuran. The analogous reduction of Zn(C5Me 4R)2 (R = H, SiMe3, But) yields only decomposition products, but the isotopically labeled dimetallocene 68Zn2(η5-C5Me5) 2 and the related compound Zn2(η5-C 5Me4Et)2 (2) have been obtained by this procedure. Compound 2 has lower thermal stability than 1, but it has been unequivocally characterized by low-temperature X-ray diffraction studies. As for 1 a combination of structural characterization techniques has provided unambiguous evidence for its formulation as the Zn-Zn bonded dimer Zn 2(η5-C5Me4Et)2, with a short Zn-Zn bond of 2.295(3) A indicative of a strong Zn-Zn bonding interaction. The electronic structure and the bonding properties of 1 and those of related dizincocenes Zn2(η5-Cp′)2 have been studied by DFT methods (B3LYP level), with computed bond distances and angles for dizincocene 1 very similar to the experimental values. The Zn-Zn bond is strong (ca. 62 kcal-mol-1 for 1) and resides in the HOMO-4, that has a contribution of Zn orbitals close to 60%, consisting mostly of the Zn 4s orbitals (more than 96%).
