119850-87-2Relevant academic research and scientific papers
Diverse reaction courses in the controlled carbometalation of heterocumulenes with zirconium-diene complexes and molecular structures of carbon dioxide, isocyanate, and ketene 1:1 and 1:2 inserted compounds
Yasuda, Hajime,Okamoto, Takuji,Matsuoka, Yoshihiko,Nakamura, Akira,Kai, Yasushi,Kanehisa, Nobuko,Kasai, Nobutami
, p. 1139 - 1152 (2008/10/08)
The carbometalation of various heterocumulenes (carbon dioxide, isocyanates, ketenes) was systematically investigated by using a series of zirconium-diene complexes of the type ZrL2(s-cis-diene) and ZrL2(s-trans-diene) (L = η5-C5H5, η5-C5Me5; diene = butadiene, isoprene) to clarify the essential factor(s) in determining the regio- and stereochemistry of the products. The mode of CO2 insertion reaction changes drastically depending upon the bulkiness of the auxiliary ligand and the geometry (s-cis, s-trans) of ligated dienes. The 1:1 reactions of the ZrL2(butadiene) complex with t-C4H9NCO, C6H5NCO, or C6H5(CH3)CCO yield Zr-O bound complexes having (σ,syn-η3-allyl)metal structures, while the isoprene derivatives always give seven-membered-ring (Z)-oxametallacyclic isomers. The use of a bulky ketene, Ph2CCO, resulted in an abnormal addition that provides a unique six-membered oxametallacycle. (C5Me5)2Zr[C4H6C(=O)O] belongs to the monoclinic space group P21/n with a = 8.816 (1) A?, b = 28.916 (3) A?, c = 9.388 (1) A?, β = 108.89 (1)°, and Z = 4. (C5Me5)2Zr[C4H 6C(=N-t-Bu)O] crystallizes in space group Pbca with a = 14.458 (2) A?, b = 16.677 (3) A?, c = 22.446 (3) A?, and Z = 8. A 1:2 adduct, (C5Me5)2Zr[OC(=NC6H 5)C4H6C(=NC6H5)O], crystallizes in space group P212121 with a = 9.082 (2) A?, b = 17.275 (3) A?, c = 22.301 (4) A?, and Z = 4. The six-membered oxametallacycle (C5Me5)2Zr[CH=C(CH3)CH(CH 3)C(=C(C6H5)2)O] crystallizes in space group P21/c with a = 12.282 (3) A?, b = 16.082 (3) A?, c = 17.981 (4) A?, β = 108.56 (3)°, and Z = 4. Thus, the configuration of the β-carbon (sp2, sp3) in the product together with the steric bulk of substituents on C(2) and/or C(3) of the ligated diene is found to be crucial in determining the reaction courses and the regio- and stereochemistry of the products.
